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The third part of the duodenum is the longest and most posterior.
retroperitoneal as is the rest of the duodenum. It is distensible on
It lies horizontally and crosses the midline from right to left. The
barium studies and is known as the duodenal cap. It has the poste-
pancreas is superior to it. It passes behind the superior mesenteric
rior surface of the liver and the gall bladder as anterior and superior

38
The abdomen dominic blunt


vessels and anterior to the aorta and inferior vena cava. The superior differences in the appearance of the mucosal fold pattern. The
mesenteric vessels enter the root of the small bowel mesentery which mucosal folds (valvulae conniventes) are more prominent in the
passes across its anterior surface. jejunum becoming less visible or even absent towards the distal
The shortest part of the duodenum is the fourth part which passes ileum. The jejunum is slightly wider than the ileum (2.5 cm vs. 2 cm).
superiorly and to the left. It lies on the psoas muscle and left side of the The loops are convoluted and coiled within the peritoneal cavity and
aorta and loops of small bowel lie anterior to it. It becomes jejunum anchored by the small bowel mesentery to the posterior abdominal
where it emerges from the retroperitoneum at the level of L2. wall. The root of this mesentery runs inferiorly and across the midline
The duodenum receives its blood supply from branches of the from the duodenojejunal ¬‚exure on the left side, to the right lower
celiac artery, mainly via the gastroduodenal branch, and from part of the posterior abdominal wall overlying the right sacroiliac
branches of the superior mesenteric artery. These arteries give rise to joint. This mesentery consists of two layers of peritoneum within
a network of small vessels supplying the duodenum and pancreas. which run the vessels supplying the small and much of the large
Barium studies (Fig. 5.6) and cross sectional imaging (Fig. 5.7) are bowel and lymphatics as well as some fat. As the small intestine is so
the main radiological tools used for studying the duodenum. convoluted, this fan-like mesentery has a similarly folded appearance.
Endoscopy has replaced barium for much of its investigation. The blood supply is via the superior mesenteric artery, the branches
of which radiate out within the mesentery. The venous drainage and
lymphatic drainage is within the mesentery also.
Jejunum and ileum
The anterior relation is the transverse colon and the greater
omentum. The posterior relation is peritoneum overlying the struc-
The jejunum and ileum comprise the most important part of the
tures within the retroperitoneum.
alimentary tract for absorption of nutrients and form the longest
section. The transition from jejunum to ileum is a gradual one, the Radiologically, as with the rest of the gut, barium studies are com-
jejunum being the initial two-¬fths of this length of bowel. There monly used to investigate the small bowel (Fig. 5.8). This can be drunk
are differences in the arterial anatomy from jejunum to ileum, and by the patient as a barium follow-through, or introduced via a nasojeju-
nal tube as a small bowel enema (enteroclysis). Particularly in cases of
bowel obstruction, gas is seen within the small intestine on plain radi-
ographs of the abdomen. CT and MRI investigate the small bowel and
its relationship to other organs (Fig. 5.9), and both of these cross-
sectional techniques can be employed with contrast in the bowel lumen
Pyloric canal

to produce cross-sectional images.
First
Gastric antrum
Ultrasound may show small bowel pathology particularly when
Part of
Second
duodenum there is an obstruction or free peritoneal ¬‚uid, and radionuclide scans
are also used to assess in¬‚ammation in in¬‚ammatory bowel disease,
Third
or ectopic gastric mucosa in a Meckel™s diverticulum (an embryologi-
cal remnant) which may produce bleeding into the gut.

Fig. 5.6. Duodenum on barium meal. Barium coats the mucosa with its
characteristic mucosal folds, and it is partly distended with gas. The short
pyloric canal accounts for the constriction between the gastric antrum and the
well-distended ¬rst part of the duodenum.




Liver

Portal vein

Pancreatic head
Jejunum
Duodenum


Ascending colon
Jejunum




Ileum




Fig. 5.7. The second, third, and fourth part of the duodenum are seen here on a
coronal reconstruction from an axial CT scan. Lying on the inside of the curve
Fig. 5.8. Small intestine on barium follow-through. Barium remains in the
formed by the duodenum is the pancreatic head and the portal vein passes
stomach.
obliquely towards the liver.


39
The abdomen dominic blunt




Transverse
colon
Superior Descending
mesenteric vein colon
Ascending
colon
Part of
superior
mesenteric artery


Sigmoid
Ileum colon

Cecum

Jejunum


Tube in
rectum




Fig. 5.10. Whole colon demonstrated on barium enema. White barium coats the
Fig. 5.9. Small intestine on a coronal CT reformat. Note the similarity with the
mucosa and the lumen is distended with gas. This image is taken with the
small bowel barium study. Some of the mesenteric vessels passing in the
patient lying on the left side, accounting for the ¬‚uid levels. There is variation in
mesentery (fat within mesentery here is black) are well shown (compare these
the length of the colon and the con¬guration of the non ¬xed parts (transverse
with the angiographic images elsewhere in this book).
and sigmoid colon).



Colon (including rectum)
The large bowel connects the terminal ileum to the anal canal. It con-
sists of the cecum, in the right iliac fossa, the ascending colon, the Stomach
Liver
transverse colon extending from the hepatic ¬‚exure on the right to
the splenic ¬‚exure in the left upper quadrant. From the left upper Transverse
colon
quadrant, the descending colon passes inferiorly to the sigmoid colon,
thence the rectum and anal canal (Fig. 5.10).
Small
The cecum is that portion of the right side of the colon inferior to bowel
the ileocecal valve where the terminal ileum enters the large bowel.
It is a blind-ended sac, which is the widest part of the large bowel and
into it enters the vermiform appendix. The cecum is a variable length
and is usually covered anteriorly and on each side by peritoneum, but
this does not completely surround it. There is some variability in this
Fig. 5.11. Coronal reformat CT showing the transverse colon. Note the stomach
and the cecum may be long and completely intraperitoneal. The
and liver superiorly and small bowel loops inferiorly.
appendix has its own mesentery (the meso-appendix) in which runs its
own artery. The length and position of the appendix is quite variable;
it may be retrocaecal and pass superiorly, or extend inferiorly into the
true pelvis. The ileocecal valve is variable in its appearance and may The splenic ¬‚exure is where the colon once more becomes
protrude into the lumen of the cecum or be ¬‚at. retroperitoneal. From the phrenicocolic ligament beneath the left
The ascending colon extends superiorly to the hepatic ¬‚exure. It is hemidiaphragm, the descending colon passes inferiorly. At the pelvic
retroperitoneal, the peritoneal re¬‚ection on its lateral side forming brim it becomes the sigmoid colon, a variable length of colon, which
a shallow potential channel called the right paracolic gutter. The is once more intraperitoneal, with its own mesocolon, the root of
hepatic ¬‚exure usually lies below the right lobe of the liver. which lies over the left sacroiliac joint and sacrum in an inverted
The transverse colon (Fig. 5.11) is invested by layers of peritoneum V-shape. As this becomes the rectum, the peritoneum is con¬ned to its
and is bowed anteriorly and inferiorly. In some subjects it may have a anterior and lateral surfaces in the upper third, over some of its ante-
long inferior loop extending into the pelvis. The peritoneal surfaces rior surface in the mid rectum. Inferiorly it is below the peritoneal
around the transverse colon anchor it to the posterior abdominal wall cavity. It joins the anal canal at the ¬‚oor of the true pelvis.
as the transverse mesocolon. The peritoneum surrounding the The cecum, ascending and descending colon lie anterior and lateral
stomach and ¬rst part of the duodenum extends inferiorly to join that to their respective psoas muscles and femoral nerves as well as to the
around the transverse colon and together these form the greater muscles of the posterior abdominal wall. Laterally lie the iliolumbar
omentum (described above). ligaments and origins of the transversus abdominis muscles. More

40
The abdomen dominic blunt


inferiorly, the colon lies anterior to the iliac bones and the iliacus
muscles. The anterior relations of each side are similar, being mainly
loops of small bowel and the lateral part of the anterior abdominal
wall. The splenic ¬‚exure lies inferior to the spleen and lower slips of
the left hemidiaphragm, the hepatic ¬‚exure is usually beneath the
Sacrum
right lobe of the liver, although it may interpose between this and the
right hemidiaphragm.
The transverse colon is the ¬rst structure encountered with the Bladder
greater omentum on opening the peritoneum. Posterior to it lie small
Rectum
Seminal
bowel loops, and the second part of the duodenum, and a part of the
vesicle
pancreatic head.
The sigmoid colon is variable in length (Fig. 5.12) and the relations
Prostate
will be dictated by this and the state of bladder ¬lling. The bladder gland
and uterus in the female lie inferiorly and anteriorly to it and, for the
most part elsewhere, it is bordered by loops of ileum. Posteriorly lies
its mesentery, the sacrum and rectum.
The rectum is bordered posteriorly by the sacrum and coccyx, the
origins of muscles of the pelvic ¬‚oor, and sympathetic nerves.
Anteriorly lie the peritoneal re¬‚ection and small bowel and sigmoid
colon superiorly, then the seminal vesicles, vas deferens, bladder, and
prostate in the male, and the vagina, cervix, and uterus in the female.
The blood supply of the large bowel is derived from the superior
Fig. 5.13. Sagittal MRI image to show the rectum surrounded by fat (white on
mesenteric artery as far as the distal transverse colon and thereafter this sequence) and small vessels anteriorly to the sacrum and posterior to the
via branches of the inferior mesenteric artery. These are discussed seminal vesicles, bladder and prostate in this male patient. Note also the angle
elsewhere. Lymphatics drain along the lines of the arteries. at the ano-rectal junction.
Gas in the colon is usually appreciated on a plain abdominal radi-
ograph. It can be imaged with barium and air in a double contrast
barium enema to give mucosal detail after strong purgative laxatives ment of the wall and the relationship of pathology to surrounding
have emptied it of stool (Figs. 5.10, 5.12), or with a water-soluble single structures (Fig. 5.11).
contrast enema simply to demonstrate a level if obstruction is sus- In cases of colonic bleeding, angiography may be used to assess
pected. During a barium enema, the patient is moved on the examina- for a bleeding point, or radionuclide scans may be used if the bleed-
tion couch to allow coating of the entire colon and optimal ing is less acute. Ultrasound may be used to assess for suspected
demonstration of the length of the colon in different projections to appendicitis and occasionally is used to observe sites of bowel wall
separate overlapping loops (although in a long tortuous bowel this thickening.
may be dif¬cult). On a barium enema, the folds of the colon wall The rectum being relatively ¬xed is well evaluated with MRI
(haustra) are demonstrated readily. These are sometimes less promi- (Fig. 5.13) particularly to investigate rectal tumors.
nent within the lower descending colon and sigmoid.
The ileocecal valve is usually identi¬able as a ¬lling defect on the
posteromedial wall of the cecum. The appendix often ¬lls with barium
Anal canal
or air.
The anal canal (Fig. 5.14) represents the ¬nal part of the alimentary
When insuf¬‚ated with air, a CT scan can give detail of the bowel
tract. It is a short (around 3 cm) tubular canal surrounded by the inter-
wall also (CT pneumocolon) and both CT and MRI may allow assess-
nal and external anal sphincter. At its junction with the rectum, the
puborectalis muscle loops posteriorly around it making the anorectal
junction of around 90 degrees. From this point, the anal canal runs
posteriorly and inferiorly to the anal verge.
The internal sphincter is continuous with the circular muscle of the
rectum, while the external sphincter superiorly is continuous with
the levator ani muscles of the pelvic ¬‚oor. More inferiorly, it com-
Sigmoid
prises a muscle sling, that runs from the perineal body to the tip of
colon
the coccyx, and below this circular ¬bers completely surround the
canal. These three components of the sphincter are often not sepa-
rated clearly from each other, and are under voluntary control. The
arterial supply to the anal canal is from the superior rectal artery and
inferiorly from the inferior rectal artery. The lymphatic drainage is
Rectum
important. Superiorly, the lymphatic channels drain to internal iliac
nodes, while the lower anal canal drains to the inguinal nodes. This
division is a function of the anal canal marking the junction between
Fig. 5.12. Barium enema image of the rectum and sigmoid colon. Note the tube in
the embryonic hindgut and the skin surface of the perineum.
the rectum. This view is taken obliquely.


41
The abdomen dominic blunt




Hepatic
flexure of Head of
colon pancreas

Gall Second part
bladder of duodenum

Inferior vena
cava
Right lobe
of liver
Splenic vein




Fig. 5.15. Axial CT image through the right lobe of the liver at the level of the gall
External anal
bladder. At this level also lies much of the head and body of the pancreas and
sphincter
Internal anal the spleen. The splenic vein is well seen posterior to the tail of pancreas.
sphincter




Fig. 5.14. Oblique Coronal MRI image through the anal canal. The thin external Hepatic
sphincter muscle laterally surrounds thicker internal sphincter. Laterally lies the veins
ischio-anal fat, superiorly is the prostate gland and bladder.
Inferior vena
Diaphragm cava



Below the pelvic ¬‚oor muscles, the anal canal is surrounded by fat.
The pyramidal-shaped fat deposits on each side are called ischiorectal
Fig. 5.16. Ultrasound image through the liver superiorly. The hepatic veins are
fossae.
seen as black tubular structures converging on the inferior vena cava. The heart
Imaging of the anal canal itself is not commonly performed as it can
lies to the right of the image.
be viewed directly from the mucosal surface. Imaging is used in the
investigation of sphincter damage (most commonly following birth
trauma) when MRI or endoluminal ultrasound are used most com- To investigate the liver tissue itself, CT (Fig. 5.16) or MRI are fre-
monly, and in the investigation of perianal abscesses and ¬stulae to quently used, and these will show focal abnormalities against the
plan the surgery needed to drain these effectively. CT is employed to background of the normal liver tissue. Injections of contrast agents
assess spread of anal tumors and MRI can also be used for this. into the bloodstream are commonly used to accentuate the differ-
ences between the normal and abnormal liver tissue. Some of these
demonstrate differences in the blood supply to the different tissues,
Liver
while some are taken up within liver tissue or tumor and therefore
allow differentiation of normal from abnormal areas. Ultrasound has
The liver is the largest solid organ and has complex anatomy. It is very
also been used recently with contrast agents with similar aims.
commonly the subject of imaging investigations as it is affected by
Liver diseases often produce variations in the ¬‚ow of blood into or
spread of tumors, as well as having its own range of diseases.
out of the liver and can be imaged with arteriography or hepatic
Ultrasound is usually the initial investigation (Fig. 5.15) and is useful
venography. Much of this information can now be shown with CT or
to categorize liver disease, suspected on blood tests, into disease
MRI. Information on ¬‚ow and its direction and velocity can be shown
affecting the drainage of bile from the liver via the bile ducts, or
with doppler ultrasound, and during operations on the liver, the ultra-
disease affecting the liver parenchyma itself. If disease is obstructing
sound probe may be placed directly onto the surface of the liver.
the bile ducts, further investigations may involve injecting iodinated
Nuclear medicine techniques also exist for evaluating the functional
contrast agents into the biliary tree. This can be performed via an
anatomy of the liver using agents excreted into the bile or taken up
endoscope in the duodenum, with access to the biliary tree via the
by the liver tissue.
ampulla of Vater (endoscopic retrograde cholangiopancreatogram
(ERCP)), or alternatively the bile ducts within the liver can be punc-
tured through the wall of the abdomen and the liver tissue (percuta-
Anatomy
neous transhepatic cholangiogram (PTC)). Magnetic resonance
imaging can also be used to show the ducts and this is less invasive The liver has a smooth anterior and superior surface, which has a rela-
than the other techniques. Oral or intravenous agents which are tively straight lower border from deep to the lower left costal margin
excreted into the bile have been used to show these on CT or plain across the midline running inferiorly and to the right deep to the right
radiographs, but this is largely superseded by newer techniques. costal margin to the lateral abdominal wall. Most of it is therefore deep

42
The abdomen dominic blunt


to ribs and costal cartilages. The posterior and inferior surface is irregu-
lar and borders numerous other intrabdominal structures. The liver is
sometimes described as containing four lobes: right, left, quadrate, and
caudate. For planning surgery, a segmental anatomical description is
used based on segments bordered by the main portal vein branches and
Liver
the three main hepatic veins. This seems initially complex, but less so Gall bladder
Common
once the plains of this division are appreciated.
bile duct Portal vein
Key to the liver anatomy is the fact that it has a dual blood
supply: arterial blood accounts for around 10% to 20% of its blood Inferior
Vena
supply and the portal vein providing the rest. This vein carries nutri-
Cava
ent-rich blood from the gut and is much larger than the hepatic
artery. The artery and portal vein branches run with the bile ducts
taking bile in the opposite direction towards the duodenum. The
hepatic veins drain directly into the inferior vena cava (Fig. 5.15). Fig. 5.17. Ultrasound image of the gall bladder. Note the thin wall. It lies beneath
the liver.
Usually there are three main veins (right, middle, and left) entering
the vena cava immediately below the diaphragm, close to the right
atrium, and a smaller one draining only segment 1 (caudate). In
of the cystic duct, the origin of the cystic artery (usually from the right
conditions restricting ¬‚ow of blood through the portal circulation
hepatic artery). These are important for laparoscopic gall bladder
(including cirrhosis of the liver), portal venous blood may enter
surgery when their appreciation is vital to avoid complications.
the systemic circulation via collateral vessels which enlarge. These are
The inferior relations of the gall bladder are the second part of the
commonly seen in the lower esophagus as varices, or within the ante-
duodenum and hepatic ¬‚exure of the colon.
rior abdominal wall where these can be visible around the umbilicus.
Such portosystemic anastomoses may also be seen in the anal canal
and around the hilum of the spleen and left kidney.
The smooth anterior surface is related to the inner aspect of ribs
Spleen
and costal margins, the inferior posterior surface is related to the
The spleen is a vascular organ located under the left hemidiaphragm.
esophagus and stomach on the left, and on the right to the gall
In normal adults it measures around 12 cm in maximum length
bladder, the second part of the duodenum, the hepatic ¬‚exure of the
and, like the liver, it has a curved superior and lateral surface
colon and the right kidney, and adrenal gland.
lying against the diaphragm and overlain by the lower ribs, and an
The site where the artery and portal vein enter the liver, and the
inferomedial surface bearing impressions from its anatomical rela-
common hepatic duct (draining bile) exits the liver, is referred to as
tions. These are the kidney posteroinferiorly, the splenic ¬‚exure
the hepatic hilum. These structures then run in the hepatoduodenal
of the colon anteriorly, and the gastric fundus posteromedially.
ligament towards the duodenum and pancreatic head. This is in a fold
Centrally in its inferior surface, the tail of the pancreas lies in
of peritoneum behind which is the entrance to the lesser sac (see
contact with it. The anterior surface has a notch between the gastric
peritoneum section).
and colic areas, which can be easily palpable when the spleen
Entering the anterior surface of the liver is the obliterated umbilical
enlarges signi¬cantly.
vein, which extends from the anterior abdominal wall within the free
The spleen is surrounded by peritoneum. Two layers from the poste-
edge of the falciform ligament. This ¬ssure within the anterior surface
rior abdominal wall separate to surround it, and rejoin at the splenic
is an easily identi¬able landmark on imaging. The peritoneal
hilum from where they continue to surround the stomach. These
re¬‚ections are described in the appropriate section.
layers form the gastrosplenic ligament.
The splenic artery is a large tortuous branch of the celiac artery,
Gall bladder
which runs superior to the body and tail of pancreas to enter the
spleen at its hilum. The splenic vein exits the hilum and runs poste-
This blind-ended sac is an outpouching from the biliary system. It
rior to the tail and body of the pancreas, forming the portal vein at its
lies immediately beneath the inferior surface of the liver (below
union with the superior mesenteric vein. There are numerous poten-
segment 4b, the quadrate lobe) in which it produces a smooth inden-
tial collateral channels that can drain splenic venous blood if the
tation. It is around 10 cm long and connected to the common hepatic
portal ¬‚ow is reduced in liver disease and these drain into the venous
duct by the cystic duct. The con¬‚uence of these gives rise to the
systems of neighboring organs, most commonly the gastric fundus
common bile duct. The fundus of the gall bladder lies close to,
and lower esophagus, and the renal vein.
or against, the anterior abdominal wall at the point where the
The spleen is easily seen with ultrasound in most individuals, but in
lateral margin of the rectus abdominis muscle meets the right
some cases CT (Fig. 5.16) or MRI are used to assess perfusion and the
costal margin.
vessels, especially following trauma to the lower chest when rib frac-
The gall bladder is most commonly evaluated with ultrasound
tures may also be present. Rarely, arteriography is used if there is
(Fig. 5.17), and gall stones or in¬‚ammatory thickening are easily appre-
disease affecting the blood supply, and an injection into the artery
ciated. It is usually covered on its inferior surface with peritoneum
allows a delayed image to show the venous drainage and the portal
although this may surround it completely. Further variations exist for
vein. White cells labelled with radio-isotopes can also be used to assess
much of the gall bladder anatomy, including variation in the relation-
splenic function.
ship of the cystic duct to the hepatic artery, the length and insertion

43
The abdomen dominic blunt




Intrahepatic
bile ducts
Splenic vein
Left lobe
of liver
Cystic duct
Superior
Pancreatic mesenteric
head artery
Pancreatic
Common duct
Left renal vein
bile duct
Inferior
vena cava Gall
bladder
Aorta




Fig. 5.18. Transverse ultrasound image of the left lobe of the liver and pancreas. Fig. 5.19. ERCP image showing the intrahepatic biliary tree, the common bile
The stomach is collapsed and accounts for the thin black lines between them. duct. The cystic duct, which is characteristically tortuous, runs from the gall
The light gray pancreas can be seen curving around the black vessels of the bladder. The pancreatic duct is also opaci¬ed. On this view the patient is
splenic vein and the beginning of the portal vein. Behind this lie the inferior oblique, which accounts for the apparent “loop” of the pancreatic duct as it
vena cava and the aorta. passes towards the X-ray detector.




Pancreas of two separate buds, whose ducts fuse variably). The most important
point is that a second more superior opening into the duodenum may
The pancreas is a non-encapsulated retroperitoneal organ with
drain the majority of the gland, with a smaller contribution from the
exocrine and endocrine function. It lies in the upper abdomen and
lower, more typical duct opening.
contains a variable amount of fat between lobules of tissue. It tapers
The relations of the pancreas are anteriorly the lesser sac of the
in size from the pancreatic head to the right of the midline, into a
peritoneum, which is a potential space between it, and the posterior
thinner neck, body, and tail, which run obliquely to the left, superi-
wall of the stomach. Superiorly and anteriorly lies the left lobe of the
orly, and posteriorly. The endocrine portion comprises the Islets of
liver. Posteriorly lie the splenic vein, the superior mesenteric vessels,
Langerhans, and these cannot be shown by standard imaging tech-
the aorta, and inferior vena cava and on the right, the portal vein and
niques. Most imaging is performed to investigate pathology relating
hepatic artery, and bile duct. The body and tail overlie the upper part
to the exocrine gland, its duct, and anatomically related structures.
of the left kidney and the tail extends towards the splenic hilum. The
The pancreas is variably seen with ultrasound due to the presence
main lateral relation of the head is the duodenum. Most of these
of overlying gas. When well seen this is a good modality for assessing
anatomical relations are separated from it by variable amounts of
it; however, CT and MRI are more reliably able to demonstrate it, as
retroperitoneal fat. In thin patients this may be almost completely
well as allowing assessment of its perfusion. Nuclear medicine tech-
absent, but in some cases there may be many centimeters separating
niques are used particularly in the assessment of endocrine tumours
it from adjacent structures.
of the pancreas by labelling, with radio-isotopes, chemical precursors
The pancreas receives its blood supply from branches of the
to the hormones they produce. Assessment of the pancreatic duct in
coeliac artery via the splenic and hepatic arteries. The main
conditions such as chronic pancreatitis can be made via direct cannu-
named branches are the pancreatica magna from the splenic artery
lation of it at endoscopy (endoscopic retrograde pancreatography)
and the gastroduodenal artery from the hepatic. This forms anasto-
(Fig. 5.19), although magnetic resonance imaging can also give some of
moses around the head and uncinate with arterial contributions
this information.
from the superior mesenteric artery. The venous drainage is simi-
The head of the pancreas lies on the inside of the curve formed by
larly into splenic vein, superior mesenteric vein and portal vein.
the ¬rst three parts of the duodenum. The superior mesenteric artery
Local lymph nodes, analogous to the arterial supply, drain towards
and vein run posterior to this, the vein being joined by the splenic vein
coeliac nodes.
to form the portal vein which then ascends behind the head and neck
to the right, obliquely towards the liver. The uncinate process of the
pancreas is the most inferior and posterior portion and hooks medially
Peritoneum and peritoneal spaces
from the head, behind the mesenteric vessels which are thus sur-
rounded by pancreatic tissue anteriorly, on the right and posteriorly. The peritoneum is the enveloping membrane, which encloses the
In the same direction as the portal vein, the hepatic artery passes intra-abdominal organs. It is essentially a closed sac, between the
towards the liver and the common bile duct transmits bile from the outer boundaries of the abdominal and pelvic cavity and the organs
liver and gall bladder towards the duodenum. These three important contained within.
tubular structures make an important landmark running parallel to The parietal peritoneum is the outer surface, which lies deep to
each other between the pancreatic head and the hepatic hilum. the abdominal wall muscles, beneath the diaphragm, above the
The pancreatic duct extends from the tail to the head of the gland pelvic organs and anterior to the structures of the retroperitoneum
and opens into the second part of the duodenum with the common posteriorly.
bile duct at the ampulla of Vater. There are a number of anatomical The visceral peritoneum is the complex, folded surface, which
variation owing to the gland™s embryology (it is formed by the fusion encloses most of the organs within the abdominal cavity.

44
The abdomen dominic blunt


In health, the peritoneal cavity contains only a small volume of ¬‚uid the main cavity behind the vessels running towards the liver hilum
enabling the structures to move freely over each other with respira- from the second part of the duodenum. This small communication is
tion, movement and gut peristalsis. There is usually slightly more called the epiploic foramen (of Winslow). This sac can accumulate ¬‚uid
¬‚uid within the peritoneum in females (and the Fallopian tubes open when the pancreas has been in¬‚amed (Fig. 5.20).
into the peritoneum, as the only site where the surface is incomplete).
Subhepatic space
The intra-abdominal alimentary tract lies within the peritoneal
cavity for the most part, but most of the duodenum and the ascending This is in free communication with the main peritoneal cavity, but
and descending colon lie in the retroperitoneum. The rectum is may be a site of local ¬‚uid accumulation in gall bladder disease.
covered anteriorly by peritoneum in its upper third. More inferiorly,
Pelvic recesses
it passes beneath the pelvic re¬‚ection of the peritoneum.
The vessels passing to abdominal organs lie within folds of peri- The uterovesical pouch is the pelvic recess between bladder and
toneum known as mesenteries. Where two layers of peritoneum pass uterus in the female, and the rectouterine pouch (also known as the
from the parietal surface to surrounding organs, these are called liga- pouch of Douglas) lies posteriorly and is frequently seen to contain
ments or omenta. These are of variable length and serve to anchor the ¬‚uid in in¬‚ammatory or malignant disease affecting the peritoneum
abdominal contents to different extents. For example, the mesentary (Fig. 5.21).
containing vessels and lymphatics passing to the small bowel is long,
allowing for the necessary changes in position during peristalsis and
The most important ligaments and omenta
following meals, while the short re¬‚ections of peritoneum from the
Greater omentum
diaphragm onto the liver keep this organ relatively ¬xed in position
as is also the case for the spleen. An apron-like fold of several layers of peritoneum extending inferiorly
Because of its complex folded nature, and because the gut passes in from the greater curve of the stomach and the transverse colon, often
several places from retroperitoneum to intraperitoneal position, there for a considerable distance. This frequently contains much fat and is
are a large number or recesses or blind-ended sacs. Many of these have the ¬rst structure seen once the abdominal cavity is opened at surgery.
names, but it must be remembered that, unless there is in¬‚ammation
Lesser omentum
causing these to be walled off, or following surgery, the whole peri-
toneal cavity is continuous, and material ¬‚ows freely within it tending These are the two layers from the inferior surface of the liver to the
to track towards the pelvic re¬‚ections as a result of gravity, and lesser curve of the stomach.
toward the subphrenic spaces (beneath the diaphragms), as these
develop a small negative pressure during respiration.


The most clinically important recesses of peritoneum
Bladder
Subphrenic spaces Uterovesical
pouch
These are where it re¬‚ects onto the spleen and liver (although a small
Uterus
area of the liver is in direct contact with the right hemidiaphragm,
Rectouterine
known as the bare area) (Fig. 5.20). pouch
(pouch of
Rectum
Douglas)
Lesser sac
This lies between the posterior surface of the stomach and the anterior
surface of the pancreas and is a blind-ended sac, communicating with
Fig. 5.21. Axial CT with contrast in peritoneal cavity to show the paravesical
spaces, the uterovesical pouch, and the rectouterine pouch (pouch of Douglas).




Stomach
Transverse
Greater
mesocolon
omentum
Jejunum
Head of Liver Root of small
pancreas bowel mesentery
Hepatoduodenal
at duodenojejunal
ligament
Liver
flexure
Root of Left paracolic
Right posterior Spleen transverse gutter
subhepatic space
mesocolon
(Morison™s pouch)
Pancreas
Duodenum

Left kidney
Right posterior
subhepatic space
(Morison™s pouch)
Kidneys


Fig. 5.20. Axial CT with contrast in peritoneal cavity to show the anterior right Fig. 5.22. Axial CT with contrast in peritoneal cavity to show the root of the
subhepatic space, the posterior right subhepatic space (Morison™s pouch), and transverse mesocolon, the root of the small bowel mesentery, the greater
the inferior recess of the lesser sac. omentum, and the duodenocolic ligament.


45
The abdomen dominic blunt


Falciform ligament
This contains the obliterated umbilical vein and therefore runs from
the umbilicus and anterior abdominal wall to a ¬ssure on the anterior
Rectum
surface of the liver.
Free fluid in
rectouterine
Uterus Coronary ligaments
pouch
(pouch of
These are the re¬‚ections of peritoneum onto the liver.
Douglas)
Bladder

Transverse mesocolon and small bowel mesentery
Fat in Utero-
These broad mesenteries fan out towards their respective parts of the
vesical pouch
gut and contain vessels and variable fat (Figs. 5.22, 5.23).
In health, the peritoneum is too thin to be demonstrable, but it can
be thickened when in¬‚amed, or in¬ltrated by tumors. Fluid within it
makes its recesses and folds easy to demonstrate, and the folds and
Fig. 5.23. Sagittal MRI which shows free ¬‚uid in the rectouterine pouch (pouch
spaces are frequently referred to when assessing pathology within the
of Douglas).
abdominal cavity.




46
Section 3 The abdomen and pelvis

Chapter 6 The renal tract, retroperitoneum
and pelvis

ANDREA G. ROCKALL
and S A R A H J . V I N N I C O M B E




Imaging methods • The kidneys and ureters
• The adrenal glands
The gross bony anatomy of the pelvis, as well as the detailed trabecu-
• The abdominal aorta and inferior vena cava (IVC) and associated
lar pattern of bone, is well demonstrated on conventional radi-
lymphatics
ographs. CT provides superior three-dimensional spatial relationships,
• The pancreas and part of the duodenum (see Chapter X)
for example, in the demonstration of bone fragments in pelvic frac-
• The posterior aspects of the ascending and descending colon
tures or the position of a ureteric calculus. MRI provides unique infor-
(see Chapter X)
mation regarding bone marrow components such as fat, hemopoietic
• The lumbosacral nerve plexus and sympathetic trunks.
tissue, and bone marrow pathology. The soft tissues of the renal tract
and pelvis are demonstrated using ultrasound, CT, and MRI, which
The kidneys
all provide complementary information. Ultrasound and MRI have the
Gross anatomy of the kidneys
advantage of not utilizing ionizing radiation. Ultrasound is the ¬rst
imaging modality used to assess the kidneys and renal tract as a basic The kidneys lie in the superior part of the retroperitoneum on either
screen, due to its easy accessibility, lack of radiation, and low cost. In side of the vertebral column at approximately the levels of L1“L4. The
the pelvis, a full bladder is needed to act as an acoustic window and right kidney usually lies slightly lower than the left, due to the bulk
to displace gas-¬lled loops of bowel out of the pelvis. Endovaginal and of the liver. The kidneys move up and down by 1“2 cm during deep
transrectal ultrasound, though invasive, can provide exquisite detail inspiration and expiration. In the adult, the bipolar length of the
of the internal anatomy of the female genital tract, male prostate and kidney is usually approximately 11 cm. Discrepancy between right and
seminal vesicles without the necessity of a full bladder. MRI provides left renal length of up to 1.5 cm is within normal limits. The upper
similar detail. The hysterosalpingogram (HSG) still has an important poles of the kidneys lie more medial and posterior than the lower
role in the evaluation of the uterine cavity and Fallopian tubes. poles (Fig. 6.1). The kidneys are surrounded by a layer of fat, the per-
Arteriography and venography are the gold standards for demon- inephric fat, which is encapsulated by the perinephric fascia (Gerota™s
strating the vasculature of the retroperitoneum and pelvis, although fascia) (Figs. 6.1 and 6.2).
MRI and contrast-enhanced CT (particularly multidetector CT) are
Structure of the kidney
used increasingly as non-invasive angiographic techniques.
The urinary tract is also investigated using iodinated contrast The kidney is covered by a ¬brous capsule, which is closely applied to
studies. These include the intravenous urogram (IVU) and the mic- the renal cortex. The renal cortex forms the outer third of the kidney.
turating cystourethrogram (MCUG). The former will normally demon- Columns of cortex (columns of Bertin) extend medially into the
strate the pelvicalyceal systems, lower ureters, and the full bladder medulla between the pyramids (Figs. 6.1 and 6.2). The renal medulla
outline, whereas the MCUG demonstrates the entire urethra during lies deep to the cortex and forms the inner two thirds. The medulla
micturition. Nuclear medicine techniques (scintigraphy) give impor- contains the renal pyramids, which are cone-shaped, with the apex
tant functional information on the renal tract. (the papilla) pointing into the renal hilum (Fig. 6.1). The medullary
rays run from the cortex into the papilla. Each papilla projects into
The renal tract and retroperitoneum the cup of a renal calyx, which drains via an infundibulum into the
The retroperitoneum is the space that lies posterior to the abdominal renal pelvis (Fig. 6.3). The renal pelvis is a funnel-shaped structure at
peritoneum and anterior to the muscles of the back. This space con- the upper end of the ureter. It normally divides into two or three
tains the following major structures: major calyces: the upper and lower pole calyces and in some cases




Applied Radiological Anatomy for Medical Students. Paul Butler, Adam Mitchell, and Harold Ellis (eds.) Published by Cambridge University Press. © P. Butler,
A. Mitchell, and H. Ellis 2007.

47
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


(a)
Gollbladder
Right adrenal gland Aorta Stomach
Superior
Spleen
mesenteric vein
Head of
Pyramid
pancreas
Superior
mesenteric
Duodenum
Papilla artery
Left adrenal gland
Inferior vena Left renal vein
Upper pole cava
left kidney
Perinephric
Renal sinus
foot
Cortex fat
Left renal cortex
Column
Medullary
of Bertin
pyramids
Gerota™s
Renal hilum Gerota™s fascia
fascia
Renal cortex
Quadratus Psoas Insertion of Aorta Perinephric fat
lumborum right crus of
Right psoas muscle Lower pole of left kidney
diaphragm


Fig. 6.1. Coronal T1W MRI through the kidneys. The upper poles lie medial in rela-
(b)
tion to the lower poles. The renal cortex has an intermediate signal intensity Inferior
vena cava
and the medullary pyramids have a low signal intensity. The renal sinus fat is of
Superior
high signal intensity. mesenteric
Pancreas
vein



a third calyx between those at each pole (Fig. 6.3). Each major calyx Duodenum
Superior
then divides into two or three minor calyces, which have a cup-shape, mesenteric
artery
indented by the apex of the accompanying renal pyramid. The renal
Right renal
hilum contains the renal pelvis, the renal artery, the renal vein and vein
left renal vein
lymphatics, all of which are surrounded by renal sinus fat (Figs. 6.1
and 6.2).
Renal Gerota™s fascia
sinus fat

Renal arteries, veins and lymphatic drainage Unopacified
Left renal
Retro-aortic
Aorta
left renal pelvis
artery
left renal vein
The right and left renal arteries arise from the abdominal aorta, at
approximately the level of the superior margin of L2, immediately
(c)
caudal to the origin of the superior mesenteric artery (see Fig. 6.22).
Right lobe
There is usually a single artery supplying each kidney, although there of liver
Aorta
are many anatomical variants, with up to four renal arteries supplying
Intrahepatic
each kidney (Fig. 6.2c). The renal artery divides in the renal hilum into IVC
three branches. Two branches run anteriorly, supplying the anterior
Right renal
upper pole and entire lower pole, and one runs posteriorly supplying Two right renal
vein
arteries
the posterior upper pole and mid pole.
Right renal
Five or six veins arise within the kidney and join to form the hilum
renal vein, which runs anterior to the artery within the renal pelvis
(Fig. 6.2). The right renal vein has a short course, running directly into
IVC
the IVC. The left renal vein runs anterior to the abdominal aorta and
then drains into the IVC. Occasionally, the left renal vein runs poste-
Fig. 6.2. (a) CT scan at the cortico-medullary phase, 40 seconds after
rior to the aorta, known as a retro-aortic renal vein. The left renal vein
administration of intravenous contrast medium. The renal cortex is brightly
receives tributaries from the left inferior phrenic vein, the left
enhancing. The renal medulla is of lower attenuation. The aorta and its branches
gonadal and the left adrenal vein.
(superior mesenteric and renal arteries) are homogeneously enhanced. (b) CT
The lymphatic drainage of the kidneys follows the renal arteries to scan at the cortico-medullary phase, just below Fig. 6.2 (a). Note the left renal
nodes situated at the origin of the renal arteries in the para-aortic vein passing posteriorly to the aorta (retro-aortic). The renal pelves are
region. unopaci¬ed at this early stage following contrast administration. (c) MR
venogram in the coronal plane demonstrates the right renal vein draining directly
into the IVC. There are two right renal arteries, an anatomical variant.
Nerve supply
Fascial spaces around the kidney
The sympathetic nerves supplying the kidney arise in the renal sympa-
thetic plexus and run along the renal vessels. Afferent ¬bres, includ- The kidney is surrounded by perirenal fat, which is completely encir-
ing pain ¬bers, travel with the sympathetic ¬bers through the cled by a fascial plane (Gerota™s fascia), which also encases the
splanchnic nerves and join the dorsal roots of the 11th and 12th tho- suprarenal gland (Figs. 6.1 and 6.2). Medially, Gerota™s fascia blends
racic and the 1st and 2nd lumbar levels. with the fascia surrounding the aorta and IVC.

48
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


(a) (b)
Upper pole Right
upper pole
right kidney nephrogram
minor calyces
T12 upper ureter
Major calyx
upper pole Right
major calyx pelviureteric
Renal pelvis
junction Sacroiliac joint
L1
Midpole minor
Infundibulum
calyx Mid-ureter
Minor calyx Lower ureter
L2
lower pole
Pelviureteric Position of
Narrowing of right
minor calyces
junction vesico-ureteric
ureter where it
junction
crosses the common
L3
Tip of L3
iliac vessels at
transverse Bladder, distended
Upper ureter pelvic brim
process with contrast


Fig. 6.3. (a) Intravenous urogram (compression view) demonstrating bilateral smooth nephrograms and opaci¬cation of the renal collecting systems. The ureters
pass anteriorly to the transverse processes of the lumbar vertebrae. (b) Intravenous urogram, full-length view of the renal tract.



Relations of the right kidney
Superiorly and anteriorly: the right suprarenal gland and the liver.
Cecum
Descending
Anteriorly: the second part of the duodenum and the right colic
colon
¬‚exure. Posteriorly: the diaphragm, costodiaphragmatic recess of the Right ureter
pleura, the 12th rib and muscles of the posterior abdominal wall. Left ureter
Right common
Left common
iliac artery
iliac artery
Relations of the left kidney Right common
Left psoas
iliac vein
Anteriorly: The left suprarenal gland, the spleen, the stomach, the muscle
pancreas, the left colic ¬‚exure, and loops of jejunum. Posteriorly: as Right iliac blade Left iliacus
muscle
for the right kidney. Right sacroiliac
Left common
joint
iliac vein

Ureters Fig. 6.4. CT scan at the level of the pelvic brim, 10 minutes following intravenous
Anatomy of the ureters contrast administration. At this time, contrast is seen within the ureters, which
Each ureter is a ¬bromuscular tube, lined with transitional mucosa, run down along the medial aspect of the psoas muscles, just anterior to the
common iliac vessels.
which is formed as the funnel of the renal pelvis narrows, at the pelvi-
ureteric junction (PUJ) (Fig. 6.3). The ureters are approximately 1 cm in
diameter and 25 cm long and run down the posterior abdominal wall Relations of the ureters
inferiorly, along the psoas muscles (Fig. 6.3). At the pelvic brim, the Anteriorly (right): the duodenum (2nd part), the right gonadal, right
ureters run anterior to the bifurcation of the common iliac vessels, colic and ileocolic vessels and the root of the small bowel mesentery,
in front of the sacro-iliac joint (Fig. 6.4). They then run down the pos- the terminal ileum and appendix. The right ureter lies lateral to the
terolateral wall of the pelvis in close relation to the internal iliac IVC.
vessels and, at the level of the ischial spines, turn anteromedially to Anteriorly (left): left gonadal and left colic vessels, loops of small
join the trigone of the bladder at the vesico-ureteric junction (VUJ), and large bowel and the sigmoid mesocolon. The left ureter lies lateral
which lies at the posterolateral angle of the bladder (Fig. 6.3). There to the aorta.
are three normal narrowings of the ureters (where stones most com- Posteriorly (right and left): the psoas muscles, and in the pelvis, the
monly impact): bifurcation of the left common iliac vessels. In the male pelvis, the
ureter passes over the seminal vesicles and then hooks under the vas
• at the pelvi-ureteric junction
deferens before entering the bladder. In the female pelvis, the ureter
• as the ureter crosses the pelvic brim
runs inferior to the uterine artery in the broad ligament of the uterus,
• at the vesico-ureteric junction.
and lies adjacent to the lateral fornix of the vagina prior to entering
the bladder.
Blood supply and lymphatic drainage of the ureters
The arterial supply to the upper ureter is from the ureteric branch of
Anatomical variants of the renal tract (Figs. 6.2(c), 6.5)
the renal artery. Branches of the gonadal artery supply the mid ureter.
Several normal anatomical variants are seen which include:
Branches of the internal iliac artery supply the lower ureter. There is
• persistent fetal lobulation
accompanying venous drainage. Lymphatic drainage is into the lateral
• vascular anomalies (see above)
para-aortic nodes and the internal iliac nodes in the pelvis.
• renal duplication (the most common type of variant)
• incomplete or aberrant migration of the kidneys during
Nerve supply to the ureters
embryogenesis.
Sympathetic nerves to the ureters arise from the renal and gonadal
plexuses (T12“L2) and, in the pelvis, from the hypogastric plexus. Persistent fetal lobulation is a relatively common ¬nding.
Afferent ¬bers return along the sympathetic pathways to enter the Embryologically, each kidney arises from separate lobes that fuse
spinal canal at the L1 and L2 intervertebral foramina. together; in some cases, the lobulation remains visible (Fig. 6.5).

49
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


Fig. 6.5. Anatomical
(a) (b)
variations of the kidney
and ureters: (a) duplex
kidney wth partial
ureteric duplication, (b)
duplex kidney, complete
ureteric duplication and
ectopic insertion of
ureter from upper pole
moiety into proximal
ureter, (c) fetal
lobulation, (d) cross-
fused ectopia.




(c) (d)




Renal duplication has an incidence of 2% and is bilateral in 20% Intravenous urogram (IVU) (Fig. 6.3) A plain ¬lm of the abdomen is
of cases. In a classical duplex kidney, there are upper and lower ¬rst obtained to identify calci¬ed renal tract stones. Iodinated contrast
pole moieties. Each moiety has a separate renal pelvis that drains into medium is then injected intravenously. The contrast medium is imme-
a separate ureter. The two ureters may join part of the way down diately concentrated in the renal tubules, resulting in a nephrogram,
between the kidney and bladder, forming a single distal ureter or, and progresses through the collecting tubules, draining into the renal
less commonly, may be duplicated throughout their length. calyces and pelvis. The cupped appearance of the calyces is well demon-
Abnormalities of migration occur less commonly. A pelvic kidney strated (Fig. 6.3). The distribution of the major calyces to the upper,
occurs in approximately 1 in 1500 deliveries. A horseshoe kidney mid, and lower poles can be seen. Each major calyx drains through an
(1 in 700 deliveries) occurs if there is fusion of the lower poles of both infundibulum into the smooth funnel-shaped renal pelvis. The upper
kidneys in the midline, with the upper poles lying on either side of ureters form at the pelvi-ureteric junction and are depicted as smooth
the vertebral column. Crossed fused ectopia is where the lower pole tubular structures running just medial to the tips of the transverse
of a normally sited kidney fuses with the upper pole of the contralat- processes of the lumbar vertebrae, joining the bladder at the vesico-
eral kidney. ureteric junction (see below).

Imaging the kidneys and ureters CT may be performed without intravenous contrast (non-contrast CT).
Ultrasound (Fig. 6.6) The renal cortex has a smooth border, may This technique is very sensitive in the identi¬cation of renal tract
be slightly lobulated and is of intermediate echogenicity. The renal stones. The structure of the kidney is best demonstrated at the
pyramids lie within the cortex and are relatively hypoechoic. The “cortico-medullary phase,” which is at approximately 40 seconds
echogenic centre of the kidney consists of the renal pelvis surrounded following the intravenous administration of iodinated contrast
by fat within the renal hilum. The renal pelvis and calyces are not medium (Fig. 6.2). The brightly enhancing renal cortex can be depicted
usually seen unless they are distended due to distal obstruction, clearly from the medulla at this phase. The central hilar fat is of
though the upper or lower parts of the ureter may be seen. The renal low attenuation. The renal hilar vessels may be clearly depicted.
artery and vein are seen within the renal hilum. On delayed imaging (at about 10 minutes), the kidney appears

50
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


(b)
(a)




Renal cortex
Renal cortex
Liver
Gall bladder


Renal pyramid Renal sinus


Renal vein

Renal sinus

IVC
Vertebral body
Psoas


Fig. 6.6. Ultrasound images showing the right kidney: (a) longitudinal and (b) axial.



homogeneous and contrast may be seen in the renal pelvis and ureters
down to the bladder (Fig. 6.4).
Liver
MRI (Fig. 6.1) The renal cortex and medulla are best depicted on T1 Inferior vena cava
weighted images, where the cortex is intermediate and the medulla is Origin of celiac
low signal intensity. The renal pelvis and ureters are best depicted on artery
Head
T2 weighted images, where the urine within them appears of very Right Lateral Pancreas
adrenal limb
high signal. left adrenal
gland
Medial gland
The anatomy of the renal vasculature may be depicted limb
Left crus
non-invasively following bolus contrast injection at CT and of diaphragm
MRI. Early images demonstrate the arterial anatomy, which is then Spleen
followed by the venous anatomy after a short delay (Fig. 6.2). Modern
Upper pole left
workstation software allows reformatting of the vessels in three Kidney
dimensions. Right crus Retrocruval Aorta
of diaphragm space

Conventional angiography Since the advent of non-invasive CT and
Fig. 6.7. CT of the adrenal glands (arterial phase image). The adrenal glands are of
MR angiography, this invasive technique is reserved as the de¬nitive
soft tissue attenuation, surrounded by low attenuation fat.
test for demonstrating renal arterial anatomy and accessory vessels
prior to a procedure such as stenting.
the kidneys by the perinephric fat, within Gerota™s fascia. The glands
The suprarenal glands (Figs. 6.1, 6.7) consist of an outer cortex and an inner medulla.
The right and left suprarenal glands (suprarenal glands) are endocrine The glands measure up to 5 cm in length and each limb measures
glands, which lie anterior and superior to the medial aspect of the between 2 mm and 6 mm transversely. The right adrenal gland usually
upper pole of the kidneys, at the level of T12. They are separated from has an “arrowhead” con¬guration. It lies posterior to the IVC, just

51
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


above the upper pole of the right kidney. The left adrenal gland may CT The glands are usually clearly seen as arrowhead or triangular soft
have a pyramidal or crescentic con¬guration and lies along the antero- tissue density structures, surrounded by the perinephric fat (Fig. 6.7).
medial aspect of the left upper pole of kidney, between the upper pole The glands are best depicted using ¬ne sections through the gland (3“5
and the renal hilum. mm) following intravenous contrast medium. The limbs should be
approximately the same width as the adjacent crus of diaphragm.

Blood supply and lymphatic drainage of the suprarenals
MRI (Fig. 6.1) The glands may be seen clearly on both axial and
The arterial supply of the adrenals is from branches of the aorta,
coronal images, particularly if surrounded by adequate perinephric fat.
renal, and inferior phrenic arteries. A solitary vein drains directly into
the IVC on the right and into the left renal vein on the left. Lymphatic
The pelvic viscera
drainage is to the lateral para-aortic nodes.
The bladder and urethra
The bladder
Nerve supply of the suprarenals This is situated behind the pubic bones (Figs. 6.8 and 6.9). In the adult
The nerve supply derives from the preganglionic sympathetic ¬bers of the empty bladder, which is pyramical in shape, lies entirely within the
the splanchnic plexus. Preganglionic ¬bres from the splanchnic pelvis. The apex lies behind the upper border of the symphysis. The
nerves also directly innervate cells of the adrenal medulla, to produce ureters enter the posterolateral angles of the triangular bladder base.
catecholamines. The inferior angle or neck gives rise to the urethra, surrounded by the
involuntary internal urethral sphincter. Posteriorly lies the vagina in
the female and the vasa deferentia and seminal vesicles in the male.
Relations of the suprarenal glands
These structures are separated from the rectum by the rectovesical
Right: The diagphragm lies posteriorly, with the right crus of
fascia. The superior surface of the bladder is completely covered by
diaphragm lying posteromedially. The upper pole of the right kidney
peritoneum. In the male, the neck of the bladder rests on the prostate
lies inferolaterally and posteriorly. The IVC and right lobe of liver lie
gland, whereas in the female it rests directly on the pelvic fascia above
anteriorly.
the urogenital diaphragm. When the bladder ¬lls, it becomes ovoid and
the superior surface rises extraperitoneally into the abdomen.
Left: The diaphragm and left crus of diaphragm lie posteromedially.
Internally, the bladder wall is trabeculated except at the trigone, the
The upper pole of the left kidney lies posterolaterally. The peritoneum
triangular area between the two ureteric ori¬ces superiorly and the
of the lesser sac, the stomach, the spleen, the splenic vein, and pan-
urethral ori¬ce inferiorly.
creas lie anteriorly.
The blood supply to the bladder is from the superior and inferior
vesical arteries. The veins of the vesical plexus drain to the internal
iliac veins. Lymph drainage is to the internal iliac, thence to the para-
Imaging the suprarenal glands
aortic lymph nodes.
Ultrasound The suprarenal glands may be imaged in neonates when
they are relatively large in relation to the kidneys. The glands gradu-
Imaging The bladder and ureters are opaci¬ed after intravenous
ally atrophy and are much more dif¬cult to visualize on ultrasound in
urography (Fig. 6.3). In women, the fundus of the uterus indents the
adults.




(a) (b)
Superficial epigastric artery External iliac artery and
Prostate Preprostatic space
vein with calcification Spermatic cord
in wall of artery
Rectus abdominis m. Inferior epigastric
Femoral vein Symphysis pubis
vessels and vas deferens Superficial and
profunda femoris
Iliopsoas m.
Sartorius m. arteries
Full bladder
Sartorius m. Rectus
femoris m. Pectineus m.
Gluteus
Tensor fascia
Acetabulum medius m. Adductor
lata m. longus m.
Gluteus
Iliotibial tract
Iliopsoas m.
minimus m.
Obturator
Greater
internus m. Vastus
Obturator trochanter
lateralis m.
vessels and
Quadratus
nodes
femoris m.
Obturator
externus m.
Ureter
Seminal
Coccyx Ischium Gluteus maximus m.
vesicle Obturator
internus m.
Levator Anus Ischiorectal Sciatic nerve
Internal iliac Rectum Sacrum, coccyx Gluteus maximus m.
ani m. fossa
vessels (air filled)




Fig. 6.8. Axial CT of the male pelvis at the levels of (a) the acetabulum and (b) the symphysis pubis.


52
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


(b)
(a)
Common iliac vessels L5/S1 disc


Thecal sac
Thecal sac
Subcutaneous
Spinous
fat
Rectum
process of L5
Rectus
abdominis
S1 vertebral
Rectus Seminal
body
abdominis m. vesicle

Bladder
Seminal vesicle Urethra
Urinary
bladder
Rectum Transition
Symphysis
zone and
pubis
Prevesical space central
Coccyx
(extraperitoneal) zone of
Buck™s fascia prostate
around corpora
Levator ani m. (inner gland)
of penis
Symphysis
pubis Prostate Denonvillier™s
Corpus fascia
cavernosum
Tunica Anal canal
albuginea Peripheral zone
around corpora of prostate
Puboprostatic
of penis Testis
ligament
Anal canal

Corpus Bulbospongiosus m. Bulb of penis
Corpus spongiosum Bulbospongiosus Perineal body
cavernosum



Fig. 6.9. Sagittal MR images of the male pelvis: (a) Tl weighted and (b) T2 weighted.




dome of the bladder. In the male, the prostate gland may protrude up (a)
into the bladder base (the “prostatic impression”). The full bladder
Iliac arteries
Psoas m.
outline is smooth and regular, whereas after micturition, small
amounts of contrast medium are seen trapped between the mucosal Iliacus m.

folds. The bladder can be ¬lled with contrast retrogradely as part of a Ilium
Bowel loops
micturating cystourethrogram (MCUG).
Acetabulum
On ultrasound of the full bladder, the echogenic wall should not Urinary bladder
exceed 4 mm in thickness (see Fig. 6.16). The bladder contents are Femoral head
Obturator
trans-sonic. On CT, the bladder is best appreciated when ¬lled with externus m.
Perivesical
urine or contrast (Fig. 6.8). It has a rectangular shape and a wall thick- plexus
Corpus
ness less than 4“5 mm. MR is ideal to demonstrate the relationships of cavernosum
Superior pubic
the bladder in the coronal and sagittal planes (Figs. 6.9 and 6.10). ramus
Ischiocavernosus m.

The male urethra Symphysis
pubis Bulb of penis
The male urethra is approximately 20 cm long and is divided into pos-
Suspensory
terior (prostatic and membranous) and anterior (spongy) parts. The Bulbospongiosus m.
ligament of
posterior urethra is 4 cm long and the anterior approximately 16 cm. penis

The prostatic urethra is 3 cm long. It is the widest part of the Dorsal vein
urethra. On its posterior wall is a ridge, the urethral or prostatic crest. of penis
Buck™s fascia Penile urethra
In the middle of the crest is a further prominence, the verumon-
tanum. On either side of this, the ejaculatory ducts (the common ter-
mination of the seminal vesicles and vasa deferentia) open.
Fig. 6.10. Coronal T2 weighted MR images of the male pelvis: (a) to (c), from
The membranous urethra, 1.5 cm long, runs through the external
anterior to posterior. (Note chemical shift artifact from superior mid inferior
urethral sphincter within the urogenital diaphragm. This is the nar- bladder walls, anterior.)
rowest, most ¬xed part of the urethra and is therefore most prone to
injury.
The spongy urethra is further subdivided into the bulbous and urethra is well visualized in this way, but demonstration of the poste-
penile urethra. It is surrounded by the corpus spongiosum. The long rior urethra may necessitate an MCUG (see above). It is also possible to
penile urethra is relatively narrow apart from a dilatation within the image the anterior urethra with ultrasound.
glans penis, the navicular fossa. The external urethral ori¬ce is narrow
The female urethra
and calculi may lodge at this site.
This is 3“4 cm in length and extends from the neck of the bladder to
Imaging The urethra may be outlined with contrast medium retro- the vestibule, where it opens 2.5 cm behind the clitoris. The female
gradely, with a balloon catheter in the navicular fossa. The anterior urethra may be visualized during MCUG.

53
andrea g. rockall and sarah j. vinnicombe
The renal tract, retroperitoneum and pelvis


(b) (c)
S1 (sacral promontory) Median sacral artery Ventral sacral foramen


Sacroiliac joint
Bifurcation of
common iliac Gluteus medius
artery

Sigmoid colon
Sacral plexus
Sigmoid colon
Periprostatic Seminal vesicle
venous plexus Superior gluteal
Bladder
vessel
Obturator
Obturator internus m.
Inner gland of Periprostatic
internus m.
prostate and perivesical
(predominantly Levator ani m.
venous plexus
central zone)
Levator
prostatae Ischium
Anal canal
Peripheral zone
(anterior fibres
of prostate
levator ani m.)
Quadratus
Ischiorectal fossa femoris m.
Bulb of penis
Urogenital
Superficial
diaphragm
transverse
Bulbospongiosus m.
perineal m.



Crus of penis Ischiocavernosus m.



Fig. 6.10. Continued



(a) Fig. 6.11. Diagrams of
(b)
the zonal anatomy of
Ampulla of
Vas deferens
seminal vesicle the gland. (a) coronal;
Sup.
Ejaculatory
Base (b) sagittal; (c) and
duct
(d) axial at two different
Post Ant
levels.
Anterior
Level 1
¬bromuscular stroma
Central zone
Level 2 Transition zone
Verumontanum
Urethra
Peripheral zone
Inf.
Urethra
Apex




(c) (d)

Level 1 Ant Level 2 Ant




Urethra
Ejaculatory
duct

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