. 4
( 10)


Post Post

The male genital tract anteriorly. Laterally are the anterior ¬bers of the levator ani. Posteriorly
The prostate gland lie the paired seminal vesicles. A ¬brous sheath containing the peripro-
The prostate gland is a pyramidal ¬bromuscular gland, 3.5 cm long, static venous plexus surrounds it.
which surrounds the prostatic urethra from the bladder base to the The ejaculatory ducts pierce the upper part of the posterior
urogenital diaphragm (Figs. 6.9, 6.10, and 6.11). The base, superiorly, surface of the prostate and open into the prostatic urethra as
is continuous with the bladder neck. The arch of the pubis lies described above.

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

The gland is divided into glandular and non-glandular tissue. The Imaging On TRUS, the seminal vesicles appear as convoluted tubules,
glandular tissue is subdivided into the peripheral zone or PZ (70%), which contain transsonic ¬‚uid. They are less echogenic than the adja-
the central zone or CZ (25%) and the transition zone or TZ (5%). cent prostate. On CT, the seminal vesicles characteristically form a
The non-glandular ¬bromuscular stroma encircles the urethra “bow tie” appearance in the groove between the bladder base and
anteriorly. Fig. 6.11 illustrates the zonal anatomy of the prostate prostate (Fig. 6.8). On T2W MR sequences the ¬‚uid-containing seminal
diagrammatically. vesicles return a high signal (Fig. 6.10). The seminal vesicles are sepa-
The arterial supply to the prostate gland is from the inferior vesical rated from the bladder by a high signal fat plane (Fig. 6.9).
and middle rectal arteries. Venous drainage is via the periprostatic
The testis, epididymis, spermatic cord and vas deferens
plexus to the internal iliac veins and the vertebral venous plexus.
Lymphatic drainage is to the internal iliac and obturator lymph nodes. The testes are ovoid reproductive and endocrine organs responsible
for sperm production (Fig. 6.13). They lie within the scrotum, an out-
pouching of the lower anterior abdominal wall, suspended by the
Imaging The prostate gland can be imaged by transabdominal ultra-
spermatic cord. Each testis has an upper and lower pole and measures
sound but transrectal ultrasound (TRUS) is superior (Fig. 6.12). The
4 cm by 2.5 cm by 3 cm. Each testis is surrounded by a tough ¬brous
seminal vesicles are seen as hypoechoic sacculated structures postero-
capsule, the tunica albuginea, thickened posteriorly to form a ¬brous
superior to the gland.
septum, the mediastinum of the testis, in which the testicular vessels
On CT, the prostate is seen as a rounded homogeneous soft tissue
run. From here, ¬brous septa divide the gland into 200“300 seminifer-
mass up to 3 cm in diameter.
ous lobules, each containing 1“3 seminiferous tubules. These drain to
On MRI, the gland is of uniformly low signal on T1W sequences, but
the mediastinum, from whence 10“15 efferent ducts pierce the tunica
T2W sequences demonstrate the zonal anatomy. The normal PZ has
high signal intensity, as does the ¬‚uid within the seminal vesicles,
whereas the CZ and TZ have relatively low signal. The term ˜central (b)
gland™ is often used to indicate the combined CZ and TZ. The anterior
¬bromuscular stroma is low signal on all sequences. Figures 6.8, 6.9,
and 6.10 demonstrate the anatomy of the bladder and male genital
tract in the sagittal, axial and coronal planes.

Inner gland “
The seminal vesicles and ejaculatory ducts transition zone,
The seminal vesicles are two lobulated sacs, about 5 cm long, which
glands and
lie transversely behind the bladder and store semen. The terminal muscle
parts of the vasa deferentia lie medially. Posteriorly, the seminal vesi-
cles are separated from the rectum by Denonvillier™s fascia. Inferiorly, zone
each seminal vesicle narrows and fuses with the ampulla of the vas
deferens to form the ejaculatory ducts, each about 2 cm long.

Rectal wall

(a) Transducer

Bladder Urethra stroma


Seminal Peripheral Inner Transrectal Apex of gland
vesicle zone gland ultrasound

Fig. 6.12. Transrectal ultrasound of the prostate gland: (a) longitudinal scan
through the midline demonstrating the line of urethra, (b) transverse images of
the prostate.

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

The vas deferens is a muscular tube, 45 cm long, which conveys
Fig. 6.13. Ultrasound
Sup images of the testis: sperm to the ejaculatory ducts. The vas traverses the scrotum and
(a) longitudinal, spermatic cord to the deep inguinal ring, then runs back on the
(b) transverse and
lateral pelvic wall to the ischial spine, where it turns medially to the
Head (c) longitudinal scans
bladder base, looping over the ureter. Its terminal dilatation, the
through the head of the
ampulla, joins the seminal vesicle as described above.
epididymis (note typical
streak artifact).
Imaging At ultrasound, the testis has homogeneous medium level
echoes throughout (Fig. 6.13). Coronal scans show the mediastinum as
a line of high echogenicity posteriorly.
The epididymis is of similar, or slightly greater, echogenicity to the

testis. The head of the epididymis, approximately 7“8 mm diameter,
Mediastinum testis

rests on the superior pole of the testis (Fig. 6.13).
The body and tail gradually decrease in thickness inferiorly to
(b) Sup
1“2 mm. Duplex and color ¬‚ow Doppler studies can demonstrate
¬‚ow within the testicular arteries and veins.
At CT, the spermatic cord can be seen within the inguinal canal as a
thin-walled, oval structure of fat attenuation containing small struc-
Lat M
tures representing the vas and spermatic vessels (Fig. 6.8).
MR also provides excellent detail of the testis, having a homoge-
neous medium to low signal intensity on T1W images and high signal
intensity on T2W images. The ¬brous tunica albuginea is of low signal
on all sequences. T2W images best depict the lower signal intensity of
the mediastinum testis.

Vas deferens Epididymis
The penis
The root of the penis is described in the section on the perineum. The
(c) body of the penis comprises the two corpora cavernosa dorsally,
separated by an incomplete ¬brous septum, and the ventral corpus
spongiosum surrounding the urethra. All three corpora are covered
Globus Testis
by a tough tube of fascia, the tunica albuginea, and Buck™s fascia,
continuous with the suspensory ligament of the penis, attached to the

symphysis pubis. Distally, the corpus spongiosum expands to form the
glans penis, which covers the distal corpora cavernosa. The arterial
supply to the penis is from the dorsal artery, the artery to the bulb
and the arteries to the crura. Venous drainage is mainly via the cav-
ernous veins and the deep dorsal vein, which then drain to the inter-
nal pudendal veins. Lymphatic drainage from the body is to the
super¬cial and deep inguinal nodes.

near the upper pole to enter the head of the epididymis. The efferent
Imaging Ultrasound examination of the penis demonstrates low-
ducts fuse to form a single convoluted tube, which makes up the body
level echoes within the corpora; the urethra is seen as a circular
and tail of the epididymis.
anechoic structure. Color ¬‚ow and pulsed wave Doppler techniques
The epididymis lies posterolateral to the testis. It has a head superi-
allow visualization of the penile arteries, which is important in
orly, a body, and tail. Its overall length is 6“7 cm and it consists of the
the assessment of erectile dysfunction. MRI may be used in the assess-
single convoluted duct. From the tail, the vas deferens ascends medi-
ment of congental anomalies of the penis.
ally to the deep inguinal ring, within the spermatic cord.
The spermatic cord extends from the posterior border of the testis,
The female genital tract
on its medial side, to the deep inguinal ring. It contains the vas defer-
The labia majora
ens, the testicular artery, and veins, the genital branch of the gen-
The labia majora correspond to the scrotal sac of the male. The
itofemoral nerve and lymph vessels.
vestibular bulbs lie on either side of the vestibule into which
The testicular artery arises from the aorta at the level of the renal
the vagina and urethra open; they have erectile tissue and are covered
vessels. The scrotum is supplied by the external pudendal branch of the
by the bulbospongiosus muscles and the skin of the labia minora.
femoral artery. Venous drainage is via the pampiniform plexus of veins
above and behind the testis, which becomes one single vein in the
The vagina
region of the inguinal ring. The testicular vein ascends to the IVC on
the right and the renal vein on the left. Lymphatic drainage accompa- The vagina is a muscular tube, approximately 8 cm long, which
nies the testicular vessels to para-aortic lymph nodes at the level of Ll-2, extends up and back from the vulva to surround the cervix of the
whereas the scrotum drains to the super¬cial inguinal lymph nodes. uterus (Fig. 6.14). The vagina has anterior and posterior walls,

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

(a) (b)
L5 CSF in thecal sca
Thecal sac and
nerve roots
Subcutaneous fat
S1 Anterior fornix
Rectus abdominis
of vagina
Mesentery and
mesenteric vessels
L5/S1 intervertebral Internal os
Cervical canal
small bowel
Fluid-filled bowel
Posterior fornix Rectum
of vagina
Myometrium Endocervical canal
Junctional zone
External cervical os
Junctional zone
Bladder Fibrous cylinder
of cervix
Pre-vesical space
Anterior fornix
Anococcygeal body Urinary bladder
Bladder neck of vagina

Anal canal Symphysis pubis

Crus of clitoris
Superficial transverse perineal m. Levator ani
Vagina Vestibule Perineal body

Fig. 6.14. (a) Sagittal and (b) parasagittal T2 weighted images of the female pelvis, demonstrating the zonal anatomy of the uterus.

normally in apposition. Superiorly, the cervix divides the vagina into
Rectus abdominis m. Bladder
shallow anterior and deep posterior and lateral fornices.
Anterior to the vagina are the bladder base and urethra. Posteriorly
is the rectouterine pouch of Douglas and the ampulla of the rectum. External iliac
Acetabulum artery and vein
The urethra, vagina, and rectum are all parallel to each other and to
the pelvic brim. Iliopsoas m.
Blood supply is via the vaginal artery and the vaginal branch of the minimus m.
uterine artery. The vaginal veins form a plexus that drains to the inter- Follicular cyst
in ovary
nal iliac veins. Lymphatic vessels from the upper two-thirds drain to
the internal and external iliac nodes and from the lower third to the Ovary
inguinal nodes. medius m.
Superiorly the vagina is supported by the levator ani, the transverse
Uterus Piriformis m.
cervical (cardinal), pubocervical, and uterosacral ligaments, all (myometrium)
attached to the vagina by pelvic fascia. Inferiorly, support is provided
by the urogenital diaphragm and perineal body.
Endometrium Sacrum Gluteus maximus m.

The uterus (Fig. 6.14 and 6.15) Fig. 6.15. Axial CT of the female pelvis at a level above the acetabulum to show
The uterus is a pear-shaped muscular organ, approximately 8 cm long, the normal uterus and ovaries.
5 cm across and 3 cm thick. It has a fundus, body and cervix. The
Fallopian tubes enter each superolateral angle (the cornu). The body
narrows to a waist, the isthmus, below which lies the cervix,
embraced by the vagina. accompanies the artery and drains into the internal iliac vein.
The cavity of the uterus is triangular in coronal section, but is a Lymphatic vessels drain to internal and external iliac lymph nodes
mere cleft in the sagittal plane. The cavity communicates with the cer- and para-aortic nodes.
vical canal via the internal os, and the cervical canal opens into the Uterine ligaments and supports include: (a) the levator ani muscles;
vagina via the external os. (b) the transverse cervical, pubocervical, and uterosacral ligaments,
Peritoneum covers the entire uterus except below the level of the (c) the broad and round ligaments.
internal os anteriorly, where it is re¬‚ected on to the bladder, and later- The broad ligaments are formed by anterior and posterior
ally between the layers of the broad ligament. The thick smooth re¬‚ections of peritoneum passing over the Fallopian tubes. They
muscle myometrium is related directly to the endometrium with no enclose the parametrial connective tissue in addition to the round
intervening submucosa. The endometrium is continuous with the ligaments, uterine vessels, and accompanying lymph channels and
mucous membrane of the uterine tubes and the endocervix. ovarian ligaments laterally.
The main arterial supply of the uterus is the uterine artery, which The uterine tubes
passes to the uterus in the base of the broad ligament, crossing above Each Fallopian tube is about 10 cm long and lies in the free edge of
the ureter. The artery anastomoses with the ovarian artery. The vein the broad ligament, extending out from the uterine cornua to form a

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

funnel-shaped lateral part, the infundibulum, which extends beyond (a)
the broad ligament and overhangs the ovary with its ¬nger-like
Bladder wall Bladder
Arterial supply is from the ovarian and uterine arteries and there is Fundus of
corresponding venous drainage. Lymphatic drainage is chie¬‚y to para-
aortic lymph nodes. Endometrium
Vagina with
thin echogenic
The ovaries
These paired almond-shaped reproductive and endocrine organs lie Cervix uteri
in the ovarian f™ossae, situated in the lateral pelvic sidewalls. Their
size and appearance varies with age. Normal adult dimensions are
3 1.5 2 cm with a weight of 2“8 g and each ovary contains a few
mature follicles, 70 000 immature follicles, and postovulatory (b)
corpora lutea and corpora albicantia (scarred areas marking the site
of previously ruptured follicles). After the menopause, the ovary atro-
The ovary is attached to the back of the broad ligament by the
mesovarium. It is attached to the infundibulum of the Fallopian tube
as described above. That part of the broad ligament lateral to the
mesovarium running to the lateral pelvic wall is known as the suspen-
sory ligament of the ovary and within it run the ovarian vessels and
lymphatics. Inferiorly lies the levator ani muscle.
Arterial supply is by the ovarian artery, which arises from the
aorta at Ll/2. Venous drainage is from the pampiniform plexus into
the ovarian veins, which drain into the IVC on the right and the
renal vein on the left. Lymph drainage is along the ovarian vessels to
preaortic lymph nodes at the level of the ¬rst and second lumbar

Imaging The commonest method of investigation of the female
Fig. 6.16. Longitudinal transabdominal scans of the uterus: (a) secretory phase,
genital tract is with ultrasound. The full urinary bladder provides an
(b) proliferative phase. Note the difference in thickness of endometrium.
acoustic window through which the uterus and ovaries may be visual-
ized. In the adult the myometrium is of uniform low echogenicity
and the endometrium is seen as a highly echogenic stripe on longitu-
dinal images. The thickness of the central echogenic stripe depends
on the phase of the menstrual cycle, being maximal perimenstrually
(Fig. 6.16). Postmenopausally, the thickness and echogenicity of the
endometrium is reduced. Ovarian
The vagina is seen inferiorly on sagittal scans as a highly echogenic Developing
stripe making an acute angle with the body of the uterus. The ovaries
can usually be identi¬ed in the adnexal areas and in the adult it is
possible to see up to ¬ve or six small transsonic follicles. It is normal iliac artery
to see a small amount of ¬‚uid in the pouch of Douglas. Endovaginal
ultrasound provides much improved resolution (Fig. 6.17). It is possible
to demonstrate the vascular supply of the ovaries with color Doppler.
Fig. 6.17. Transvaginal ultrasound of the ovary, longitudinal section. The detailed
Ultrasound is capable of demonstrating most congenital abnormalities structure of the ovary and follicles can be visualized.
of the uterus.
On CT scans, the uterus is seen as a homogeneous soft tissue mass
dorsal to the bladder (Fig. 6.15), but it is not usually possible to recog- myometrium is of intermediate signal intensity, which increases in
nize the ovaries unless they are enlarged or contain cysts. The broad the midsecretory phase.
ligament appears as a thin, soft tissue density extending anterolater- On T2W images the cervix has an inner cylinder of low signal
ally from the uterus to the pelvic sidewalls. stroma continuous with the JZ. The appearances do not change with
On T2W MRI sequences in the adult (Fig. 6.14), three distinct zones the menstrual cycle or with oral contraceptives.
are seen within the uterus: the endometrium, junctional zone (JZ), Normal ovaries are low to medium signal on T1W images and
and myometrium. The endometrium and uterine cavity appear as a higher signal on T2W images. Follicles stand out as round hyperin-
high signal stripe, bordered by the low signal intensity JZ. This repre- tense foci.
sents the inner myometrium and, at the level of the internal os, it The anatomy of the Fallopian tubes and ¬ne mucosal detail of the
blends with the low signal band of ¬brous cervical stroma. The outer uterine cavity are best demonstrated by hysterosalpingography (HSG)

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

Venacaval foramen


L5 Median arcuate
Free spill
of contrast
cecum Sacrum
cornu Sacroiliac
and colon
Uterine joint Aorta
Isthmus of fundus
fallopian tube Ampulla of
Cavity of body
fallopian tube
of uterus Medial and
lateral arcuate
Left ovary in
broad ligament
Internal os
Quadratus lumborum
canal Psoas major
pubic ramus

Fig. 6.18. Normal hysterosalpingogram (HSG).

(Fig. 6.18). The uterine cavity is usually triangular and smooth walled,
leading to the narrow Fallopian tubes. Contrast should spill freely into
the peritoneal cavity.

The posterior abdominal wall Fig. 6.19. The muscles of the posterior abdominal wall.
Bones and muscles of the posterior abdominal wall
The ¬ve lumbar vertebrae run down the midline of the posterior
Diaphragm This is formed by a peripheral muscular component and
abdominal wall, separated by the intervertebral discs. The 12th rib
a central tendinous component.
forms the superior margin of the posterior abdominal wall.
The muscular part of the diaphragm is composed of:
Muscles and fascia (Fig. 6.19)
• vertebral component (the crura and the medial and lateral arcuate
Psoas The paired psoas muscles arise from the roots of the transverse
processes, the vertebral bodies and intervertebral discs of the 12th tho-
• costal component, which attaches to the inferior costal margin
racic to 5th lumbar vertebrae (Fig. 6.1 and 6.2). Each is enclosed in a
• sternal component, which attaches to the xiphisternum.
¬brous sheath derived from the lumbar fascia, which covers the inter-
The crura insert onto the anterior vertebral bodies from L1 to L3 on
nal layer of the posterior abdominal wall musculature. Each psoas
the right and L1 to L2 on the left. The crura join in the midline to form
muscle runs inferolaterally, where it is joined by the ¬bers of iliacus
a tendon, the median arcuate ligament. The medial and lateral arcuate
to form the iliopsoas muscle, passing behind the inguinal ligament to
ligaments are the fascial thickenings over the psoas and quadratus
insert into the lesser trochanter of the femur (Fig. 6.8). The nerve
lumborum muscles, giving origin to the diaphragm.
supply is from the lumbar plexus.
The central tendinous part of the diaphragm is fused with
the pericardium. It is pierced by the IVC (at T8). The aorta passes
Iliacus This paired fan-shaped muscle arises from the upper part of
through the diaphragm posterior to the median arcuate ligament,
the iliac fossa. The ¬bres join the lateral side of psoas tendon as
in the retro-crural space (at T12). The esophagus passes through
described above.
th muscular part of the diaphragm in the region of the right
crus (at T10).
Quadratus lumborum This paired ¬‚at muscle arises below from
the iliolumbar ligament, adjoining iliac crest and the tips of the trans-
Muscles of the pelvis
verse processes of the lower lumbar vertebrae (Fig. 6.2). Fibers run
The major muscles include the paired psoas and iliacus muscles,
superiorly and medially to insert into the lower border of the 12th rib.
described above. Within the true pelvis, the piriformis muscles,
The anterior surface is covered by the lumbar fascia. The nerve supply
covered by parietal fascia, arise on either side of the anterior sacrum
is via the lumbar plexus.
and pass laterally through the greater sciatic foramen to insert onto
the greater trochanter of the femur, so forming part of the posterior
Transversus abdominis This is the deepest of the three sheets of
wall of the pelvis (see Fig. 6.15).
muscle that form the anterior abdominal wall. Near the lateral border
The lateral wall of the pelvis is formed by the obturator internus
of quadratus lumborum, the muscle becomes a ¬brous aponeurotic
muscle, covering the tough obturator membrane, which overlies the
sheet that splits into two layers to surround the muscles of the poste-
obturator foramen (Fig. 6.10). A small de¬ciency anteriorly forms the
rior abdominal wall, forming the anterior and posterior parts of the
obturator canal, through which the obturator vessels and nerve pass to
thoracolumbar fascia.

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

Right Left
Deep dorsal vein
Body of clitoris
of penis
Glans of clitoris Corpus cavernosum
Crus of clitoris Corpus spongiosum
Bulb of vestibule
Crus of penis
Ischiocavernosus m.
Greater vestibular
Ischiocavernosus m.
gland Bulbospongiosus m.
Bulbospongiosus m.
Perineal body Perineal membrane
Crus of penis
Perineal membrane
Superficial transverse
Perineal branches
perineal m.
of pudendal nerve Perineal body
and internal
External anal
pudendal artery Superficial transverse
sphincter perineal m.

External anal
Inferior rectal Puborectalis Inferior rectal sphincter
artery and nerve Levator ani m.
Pubococcygeus artery
Anus Puborectalis
Levator ani m.
Gluteus maximus m.
Anococcygeal body Iliococcygeus
maximus Coccyx Coccyx

Fig. 6.20. Diagrams of (a) the female and (b) male peritoneum, viewed from below. The cross-hatching indicates the muscles overlying the crura and bulb of the
clitoris and vestibule (female) and the penis (male).

enter the thigh. The tendon of obturator internus runs through the The same muscles are present in the female although they are less
lesser sciatic foramen to insert onto the lesser trochanter of the femur. well developed (Fig. 6.20). In the midline, at the junction of the anterior
and posterior perineum, lies the ¬bromuscular perineal body, to which
the anal sphincter and perineal muscles attach (Fig. 6.20).
The pelvic ¬‚oor
The anal triangle, between the ischial tuberosities and coccyx, con-
MR, with its multiplanar capability, is particularly well suited to
tains the anus and its sphincters, levator ani and, laterally, the
demonstration of the pelvic ¬‚oor (Figs. 6.10 and 6.14). On T1-weighted
ischiorectal fossae (¬gure 10). These lie below and lateral to the poste-
sequences (T1W) the high signal pelvic fat provides excellent contrast
rior ¬bres of levator ani.
with the low signal pelvic musculature.
The pelvic ¬‚oor supports the pelvic viscera and is composed of a
The blood and lymph supply to the abdomen and pelvis
funnel-shaped sling of muscles and fascia pierced by the rectum,
The abdominal aorta
the urethra and, in the female, the vagina. The muscle groups are
The abdominal aorta is a continuation of the thoracic aorta as it
divided into:
passes through the diaphragmatic hiatus, just anterior to the 12th tho-
racic vertebra (Figs. 6.1 and 6.2), accompanied by the thoracic duct,
(a) the pelvic diaphragm superiorly: levator ani and coccygeus
azygous and hemi-azygous veins splanchnic nerves and sympathetic
(b) the perineal muscles inferiorly (Fig. 6.20): the urogenital perineum
trunks. The diaphragmatic crura envelope the anterolateral aspect of
anteriorly and the anal perineum posteriorly.
the aorta and then insert into the 1st or 2nd lumbar levels (Fig. 6.7).
The levator ani is the most important muscle of the pelvic ¬‚oor. It
The aorta runs along the anterior aspect of the lumbar vertebrae,
arises from the posterior aspect of the pubis, the pelvic fascia over
slightly to the left of the midline, down to the 4th lumbar vertebra,
obturator internus and the ischial spine.
where its terminal divisions are the common iliac arteries and the
The levatores ani act as a muscular support and have a sphincter
median sacral artery. The IVC, the cysterna chyli and the origin of the
action on the anorectal junction and vagina. They are assisted by the
azygous vein lie to the right of the aorta. The sympathetic trunk runs
small coccygeus muscles posteriorly (Fig. 6.20).
closely applied to the left side of the aorta.
The perineum is a diamond-shaped space that lies within the
Many of the branches of the aorta may be demonstrated with ultra-
ischiopubic rami and the coccyx. A line drawn between the ischial
sound (Fig. 6.21) and angiography (including CT, MR angiography and
tuberosities will pass just anterior to the anus, demarcating the
direct angiography) (Fig. 6.22):
urogenital triangle anteriorly and the anal triangle posteriorly
The branches of the aorta include:
(Fig. 6.20).
Three anterior arteries:
The anterior urogenital triangle contains the musculofascial urogen-
• celiac artery (at T12/L1), dividing into the hepatic artery and
ital diaphragm, which is pierced by the urethra in both sexes, forming
splenic arteries, supplying the liver, stomach, pancreas,
the voluntary sphincter urethrae, and by the vagina in the female.
and spleen
Below this is the super¬cial perineal pouch, which in the male con-
• superior mesenteric artery (at L1), dividing into the inferior pancre-
tains: (a) the bulbospongiosus muscle which covers the corpus spon-
aticoduodenal artery, the jejunal and ileal arteries, the middle colic,
giosum and surrounds the urethra, the whole forming the bulb of the
right colic, and ileocolic arteries, supplying the mid-gut, to the mid-
penis; (b) the paired ischiocavernosus muscles which arise from the
transverse colon
ischial ramus and cover the corpora cavernosa of the penis (Fig. 6.20).

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

Left hepatic artery Left gastric artery

Intercostal artery

Hepatic artery

hepatic artery
Splenic artery
Superior Left renal
mesenteric arteries (2)
Celiac axis

Right renal

Vertebrae mesenteric
Ileocolic artery
Jejunal branches

Fig. 6.21. Longitudinal ultrasound scan through the aorta, celiac, and superior
Lumbar arteries
mesenteric arteries.
Distal superior
mesenteric artery

• inferior mesenteric artery (at L3), dividing into the superior left colic
Fig. 6.22. Flush aortogram, frontal projection. Note the left hepatic artery arises
artery, inferior left colic arteries, and the superior rectal artery.
from the left gastric artery (a variant seen in 25% of normal individuals). The
Three pairs of lateral visceral arteries: patient has two left renal arteries.

• adrenal arteries
• renal arteries
are always visible when normal. The inferior mesenteric artery and
• gonadal arteries (testicular or ovarian).
several lumbar arteries may also be seen. Multi-detector CT or MR
Five pairs of lateral abdominal wall arteries:
angiography enable image reformatting, to demonstrate the vessels in
any anatomical plane.
• inferior phrenic arteries (supplying the diaphragm)
• four pairs of lumbar arteries (supplying the abdominal wall).
Angiography: A pigtail catheter introduced into the upper abdominal
aorta is used to inject iodinated contrast medium directly into the
Imaging the aorta
aorta, followed by rapid imaging (Fig. 6.22). Selective catheterization
Ultrasound: The abdominal aorta may be imaged from the diaphragm
of the aortic branches may also be performed.
to the bifurcation, although occasionally the distal aorta is obscured by
overlying bowel gas. It is normally 2“3 cm in diameter (Fig. 6.21).
Inferior vena cava (IVC) (Figs. 6.2, 6.7)
The IVC is formed by the union of the common iliac veins from the
CT and MRI: The aorta and its main branches are well depicted on CT
pelvis, just behind the right common iliac artery, at the level of the 4th
and MRI following intravenous contrast enhancement (Figs. 6.1, 6.2
or 5th lumbar vertebra. The IVC runs up along the anterior aspects of
and 6.7). The celiac axis, superior mesenteric artery and renal arteries

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

the lumbar vertebral bodies, just to the right of the aorta. It runs ante-
rior to the right adrenal gland and right crus of diaphragm. Superiorly,
the IVC runs through the liver (the intrahepatic IVC). It then crosses Inferior mesenteric artery
through the central tendon of the diaphragm at the level of the 8th tho-
Common iliac artery
racic vertebra to drain into the right atrium of the heart.
Median sacral artery
Tributaries that drain into the IVC closely follow the branches of
the aorta (apart from the venous drainage of the small and large
bowel, which is via the mesenteric veins that drain into the portal Internal iliac

• abdominal wall veins drain into the IVC via the right and left Iliolumbar
phrenic veins and the 3rd and 4th lumbar veins Posterior
of internal
• the right gonadal, renal and adrenal veins each drain directly into iliac artery
External iliac
the IVC
Lateral sacral
• the left gonadal and adrenal veins drain into the left renal vein, artery
which then crosses the midline and drains into the IVC Uterine
artery Inferior
• the right, middle and left hepatic veins drain into the Superior gluteal
intrahepatic IVC. artery

Imaging the inferior vena cava Uterus Deep
Ultrasound: The intrahepatic part of the IVC can be seen throughout Common iliac artery
its length, up to the junction with the right atrium. The upper abdom-
inal portion of IVC can usually be well seen, but the lower part of the
IVC, common iliac, internal and external iliac veins are often partly Obturator artery Catheter
obscured by overlying bowel gas.

CT: The IVC can be seen throughout its length. The major pelvic veins Fig. 6.23. Normal pelvic arteriogram in a female patient.
are also well demonstrated.

MRI: This is the method of choice for the demonstration of ¬‚ow in
(c) the middle rectal artery, supplying the prostate gland, seminal
the IVC. The images are best performed as an MR venogram, with
vesicles and rectum
administration of intravenous contrast medium (Fig. 6.2).
(d) the uterine artery, supplying the uterus, upper vagina, Fallopian
tubes and ovary
The pelvic vasculature
(e) the vaginal artery, equivalent to the inferior vesical artery in
A pelvic arteriogram is shown in Fig. 6.23.
the male
The aorta bifurcates in front of the fourth lumbar vertebral body at
(f ) the internal pudendal artery, supplying the genitalia in the
the level of the iliac crest into the common iliac arteries, which enter
the pelvis on the medial border of the psoas muscles, lying just ante-
(g) the superior vesical artery, supplying the upper bladder
rior to the common iliac veins. The common iliac arteries divide at the
(h) the inferior gluteal artery, which passes through the lower part
pelvic brim anterior to the lower sacroiliac joints into internal and
of the greater sciatic foramen.
external iliac arteries.
The external iliac artery runs along the medial border of psoas, Branches of the posterior division of the internal iliac artery are as
passing under the inguinal ligament to become the femoral artery. It follows:
is larger than the internal iliac artery. Just above the inguinal liga-
(a) the iliolumbar artery, supplying psoas and iliacus
ment, it gives off the inferior epigastric artery and the deep
(b) the lateral sacral artery, which supplies the sacral canal and the
circum¬‚ex iliac artery, which supply the anterior abdominal wall
muscles and skin over the back
(c) the superior gluteal artery, the largest branch of the internal
The internal iliac artery enters the true pelvis anterior to the
iliac artery, passing through the greater sciatic foramen to the
sacroiliac joint, with the ureter anterior to it. From its origin, the
gluteal region.
artery runs inferomedially, anterior to the sacrum, its length varying
from 2“5 cm. It has the most variable branching pattern of all the The internal and external iliac veins accompany the arteries. MR and
arteries in the body; the commonest pattern is described here. It CT can demonstrate the pelvic vasculature.
divides into anterior and posterior divisions at the upper border of
the greater sciatic foramen.
The anterior division courses down towards the ischial spine and
Lymphatics of the abdomen and pelvis
gives off the following branches:
Lymph nodes and lymphatic vessels accompany the major vessels
of the abdomen and pelvis and are classi¬ed accordingly. In the
(a) the obturator artery
pelvis, the internal and external iliac lymph nodes drain to common
(b) the inferior vesical artery, supplying the lower bladder, ureter,
iliac lymph nodes and thence to para-aortic lymph nodes (see below).
prostate gland and seminal vesicles

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

Pre-aortic nodes are clustered around the origins of the celiac axis, Lumbosacral plexus
the superior mesenteric artery and the inferior mesenteric artery. The lumbar plexus is formed in the psoas muscle from the anterior
These drain the gastrointestinal tract from the lower esophagus to rami of the L1 to L4 nerve roots. The nerves that form include:
half-way down the anal canal, as well as the spleen, pancreas, gall
• the iliohypogastric and ilioinguinal nerves
bladder, and part of the liver.
• the lateral cutaneous nerve of the thigh
The left para-aortic nodes are grouped along the left lateral
• the femoral nerve (L 2,3,4), which may be visualized as it runs down
aspect of the aorta. The right para-aortic nodes lie anterior
and laterally between the psoas and iliacus to enter the thigh
and lateral to the IVC. The para-aortic nodes drain lymph from
beneath the inguinal ligament
the kidneys and adrenal glands, from the testes in the male and
• the genitofemoral nerve
the ovaries, Fallopian tubes and uterine fundus in the female. The
• the obturator nerve (L2, 3, 4), which crosses the pelvic brim anterior
para-aortic nodes drain into two lymph vessels, the right and
to the sacroiliac joint, runs behind the common iliac vessels, and
left lumbar trunks. The right and left lumbar trunks join the
down the pelvic side-wall into the obturator canal (Fig. 6.8)
intestinal trunk to form the cisterna chyli. This lies just to the
• the L4 root of the lumbosacral trunk, which joins sacral roots in the
right of the aorta, behind the right crus of diaphragm, at the level
sacral plexus.
of L1/L2 and is approximately 6 cm long. The cisterna chyli then
drains into the thoracic duct (see chapter “Thorax” section titled The sacral plexus, formed from the lumbosacral trunk (L4, 5) and the
“thoracic duct”). ventral rami of the ¬rst to fourth sacral nerves, lies on the piriformis
muscle (Fig. 6.10c). The largest branch is the sciatic nerve, which may
be visualized by CT and MR as it passes through the greater sciatic
Imaging the abdominal lymphatic system
foramen into the gluteal region (Fig. 6.8b).
Ultrasound: Although the para-aortic lymph nodes in the upper
abdomen may be seen in thin patients, lymph node assessment is
Abdominal sympathetic trunk and sympathetic plexus
usually incomplete because of overlying bowel gas.
The abdominal sympathetic trunks enter the abdomen through the
medial arcuate ligaments as continuations of the thoracic sympathetic
CT and MRI: Lymph nodes can be seen when they measure approxi- trunks and run along the anterior lumbar vertebrae, then continue
mately 3 mm or more in short axis diameter. Normal para-aortic as the pelvic sympathetic chains in the pelvis, posterior to the
nodes may measure up to 1 cm in short axis diameter. Pelvic lymph common iliac vessels. They are not usually seen using current
nodes rarely exceed 8 mm in short axis diameter. imaging techniques.

Section 4 The head, neck, and vertebral column

Chapter 7 The skull and brain


Anatomical Overview subarachnoid space. Part of the meninges, the dura, forms an incom-
plete partition between the cerebral hemispheres, known as the falx
The brain is supported by the skull base and enclosed within the skull
and roofs the posterior fossa as the tentorium cerebelli. There is a gap
vault. Within, the cranial cavity is divided into the anterior, middle
in the tentorium, called the hiatus, through which the midbrain joins
and posterior fossae. The anterior and middle cranial fossae contain
the hemispheres.
the two cerebral hemispheres. The posterior fossa contains the brain-
Within the brain are a number of cavities, the lateral, third and
stem, consisting of the midbrain, pons and, most inferiorly, the
fourth cerebral ventricles, which contain CSF produced by the choroid
medulla, and the cerebellum. Twelve paired cranial nerves arise from
plexuses within the ventricles. CSF ¬‚ows from the ventricles into the
the brainstem, exit the skull base through a number of foramina, and
subarachnoid spaces over the cerebral surface and around the spinal
innervate a variety of structures in the head proper. The largest of
these foramina is the foramen magnum, through which the brainstem
Blood reaches the brain by the carotid and vertebral arteries and is
and spinal cord are in continuity. The brain is invested by the
drained by cerebral veins into a series of sinuses within the dura into
meninges and bathed in cerebrospinal ¬‚uid (CSF), circulating in the
the internal jugular veins.
Maxillary antrum Imaging overview
CT and MRI scanning are central to neuroimaging. The role of skull
radiography is very limited and arguably the only situation where it
enjoys a primary role is in the investigation of skull fractures in sus-
pected non-accidental injury in children. The relative merits of MRI
Foramen magnum
and CT in are summarized below and routine series of axial MRI and
CT are illustrated in Figs. 7.1 and 7.2.


basilar artery
Vertebral artery
hypoglossal nerve
Medulla canal

foramen of Luschka

Temporal lobe Lateral rectus
Sphenoid sinus Fig. 7.1.
Meckel™s cave Internal carotid artery
Routine T2
Trigeminal nerve
Middle cerebellar Pons weighted
Fourth ventricle axial cranial
Middle cerebellar
Inferior cerebellar MRI: (a) to (o),
peduncle base to

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.

The skull and brain paul butler

Fig. 7.1.
(f) (g)
Crista galli Continued
Optic nerve Gyrus rectus
Sylvian fissure
Pituitary gland
Posterior cerebral
Pons (upper part) Midbrain artery
Superior cerebellar Cerebellar vermis
Occipital lobe

(h) (i)
Frontal sinus Anterior cerebral
Anterior arteries
communicating artery Anterior commissure
Middle cerebral
Sylvian fissure
Optic tract
Cerebellar vermis
Mamillary body Third ventricle
at the tentorial
hiatus Quadrigeminal
Superior sagittal plate cistern

(j) (k)
Corpus callosum
Frontal operculum Body of lateral
Lentiform nucleus ventricle
Head of caudate
Internal capsule Fornix
Splenium of
Foramen of Monro
corpus callosum
Visual (calcarine) Straight sinus
Occipital horn of
lateral ventricle

(l) (m)

Body of lateral

(n) (o)

precentral gyrus

central sulcus

postcentral gyrus

The skull and brain paul butler

(a) (b) Fig. 7.2.
Frontal sinus
Frontal sinus
Cranial CT
Frontal lobe
Frontal lobe after
Sphenoid ridge
Sphenoid ridge contrast
Temporal lobe medium:
Temporal lobe
in middle in middle
(a) to (l),
cranial fossa
cranial fossa
base to

(c) (d)
Anterior clinoid

Cavernous sinus
Pituitary gland
Basilar artery
Air cells within
the petrous Cerebellum
temporal bone

(e) (f)

Internal carotid
Middle cerebral

(g) (h)

in pineal

(i) (j)

Internal cerebral vein

Choroid plexus within
lateral ventricle

sagittal sinus

The skull and brain paul butler

Fig. 7.2. Continued

• Ionizing radiation
• Streak artifacts from bone limit visualization of the adjacent struc-
tures (e.g., the contents of the middle and posterior fossae).
• Usually restricted to axial images with the patient supine, although
high quality, multiplanar views can be reconstructed on the
modern scanners.
MRI is concerned with proton (hydrogen nucleus) imaging and differ-
ent images can be produced depending on the parameters used (the
different pulse sequences). On the T1 weighted (T1W), images, gray
matter is darker (lower signal intensity) than white matter. On T2
weighted (T2W), sequences, the reverse is true. Broadly, T1W images
are good for anatomy, T2W for the detection of pathology. CT is a
digital X-ray investigation. Due to this, and somewhat paradoxically,
white matter is depicted as being darker than gray matter because of
the radiolucency of lipid-containing material.
Centrum Iodinated contrast material administered intravenously enhances
blood within the cerebral arteries, veins, and dural venous sinuses.
Enhancement is also seen in the highly vascular choroid plexuses and
in those structures external to the blood“brain barrier such as the
pituitary gland and infundibulum.
With MRI, the mechanism of enhancement with its own intra-
MRI venous contrast agent, gadolinium DTPA, is quite different but, on
Advantages T1W images, those structures which enhance become hyperintense
(i.e., whiter) with similar appearances to CT. There are some impor-
• Superior anatomical detail
tant differences, however. Rapidly ¬‚owing blood is displayed as black
• Superior contrast resolution
“signal voids,” a property shared with both air and cortical bone but
• Multiplanar capability
for a different reason (paucity of protons) (Fig. 7.3). The role of angiog-
• Better for middle and posterior cranial fossae
raphy is primarily for the diagnosis and, in some cases, for the treat-
• No ionizing radiation.
ment of vascular abnormalities. Increasingly, non- or minimally
invasive forms, magnetic resonance angiography (MRA) or CT angiog-
Disadvantages raphy (CTA), are used for diagnosis. Depending on the technique, MRA
may or may not require gadolinium DTPA. CTA necessitates an intra-
• Longer investigation
venous injection of iodinated contrast medium.
• Claustrophobia
Catheter angiography, where iodinated contrast medium is injected
• A number of contraindications relating to various metallic implants
directly into an artery (or vein), remains the gold standard. It is nearly
(surgical clips, pacemakers, etc.) and the use of high ¬eld-strength
always performed using digital subtraction, showing the vasculature
in near isolation, free of bone detail.
• Insensitive to subarachnoid haemorrhage and calci¬cation.
The cervical carotid and vertebral arteries are usually cannulated via
the femoral artery at the groin, although a brachial arterial approach
CT can be used. The cervical carotid artery can be punctured directly but
Advantages this time-honoured method is seldom used now. Angiographic inter-
pretation is the province of the specialist neuroradiologist or clinical
• Excellent for the emergency situation, both traumatic and non-
• Quick and simple for the patient
• Good for hemorrhage and calci¬cation.

Pituitary stalk

Suprasellar cistern
Posterior cerebral

Fig. 7.3. T1 weighted axial MRI after intravenous gadolinium DTPA. Suprasellar

The skull and brain paul butler

CT and MRI interpretation Sutures must be distinguished from fractures of the skull and
The way in which a scan is “read” will be determined by the patient™s important features of the former include interdigitation, sclerosis and
suspected clinical diagnosis and the initial observations on the study. predictable positions.
These same considerations will also in¬‚uence the scan protocol and The skull is invested in periosteum, both externally (pericranium)
whether contrast agents are given. In any case, a sound appreciation and internally (endosteum). The endosteum is ¬rmly adherent to the
of the normal appearances is essential. connective tissues of the sutures.
First, the ventricular system should be assessed. Are the ventricles The skull base is formed by contributions from the sphenoid, tem-
normal in size or enlarged? Is any enlargement part of generalised poral, and occipital bones centrally and from the frontal and
atrophy or is it obstructive? Are all the ventricles enlarged or, say, just
the lateral ventricles, sparing the third and fourth? In this example,
one would search for a lesion in the region of the foramen of Monro.
Next, one should look for abnormal density (CT) or signal intensity
(MRI) within the cerebral substance, comparing the two sides. Is this
associated with mass effect, manifest by sulcal effacement or distortion
of the ventricles (“shift”)? Examination of the basal CSF cisterns, with
CT, will reveal subarachnoid hemorrhage, and their effacement is a
vital clue to cerebral swelling. The appearance of the normal
quadrigeminal plate cistern resembling a smile is reassuring (Fig. 7.2(g)).
Normal scan appearances alter with age. In the normal child, for
instance, the cerebral ventricles and CSF cisterns can be very small. In
the aging population, with some normal “volume loss,” the CSF spaces
may be prominent.
There are also “review areas” on scans, which repay a second look to
identify a subtle change. For instance, on CT the interpeduncular
cistern can harbor a small amount of subarachnoid blood. On MRI, the
region of the posterior part of the third ventricle, cerebral aqueduct
and pineal gland should be studied on the sagittal image. It is also the
case that lesions seen easily on CT may not be clearly shown on MRI
and vice versa. For example, a colloid cyst of the third ventricle can be
dif¬cult to see on MRI in its typical site at the foramen of Monro.

The skull (Fig. 7.4)
The skull vault or calvarium is formed from the frontal, temporal,
parietal, and occipital bones. The skull vault consists of inner and
outer bony “tables” or diploe separated by a diploic space containing
marrow and large, thin-walled diploic veins. In children, marrow is
Sagittal suture
typically “red,” being active in blood production. It is hypointense on
Lambdoid suture Dural calcification
T1W MRI and, in the adult, is gradually replaced by “yellow” or fatty
marrow, which becomes hyperintense on T1W images. Frontal sinus
The bones of the vault are joined at various sutures, which consist Crista galli
Lesser wing
of dense connective tissue. The sagittal suture joins the two parietal of sphenoid
bones in the midline and the coronal suture joins them to the frontal plate
In the infant there is a midline defect between the frontal and pari- Floor of
Greater wing
the anterior
of sphenoid
etal bones at the junction of the sagittal and coronal sutures. This cranial
anterior fontanelle or bregma closes in the second year.
The occipital bone forms most of the walls and ¬‚oor of the posterior
cranial fossa, the largest of the three fossae. The single lambdoid suture
separates the parietal and occipital bones. The clivus is formed from the Anterior
basal portions of the sphenoid bone anteriorly and of the occipital bone clinoid
posteriorly. The articulation is known as the basisphenoid synchondro-
sis and is also the site where the petrous apex joins the clivus. Superior
Sutures are smooth in the newborn but throughout childhood, bone
interdigitations develop followed by perisutural sclerosis (increased
bone density) and ultimately fusion in the third or fourth decades Maxilla
or even later. However, for practical purposes sutural fusion occurs
in adolescence because only in children does raised intracranial
pressure, due for instance to a brain tumor, cause head enlargement. Fig. 7.4. (a) Frontal, (b) lateral skull radiographs.

The skull and brain paul butler

accounts for the frequent occurrence of traumatic contusions in the
inferior frontal lobes.
The sphenoid bone consists of a central body and greater and lesser
wings. The greater wing forms the ¬‚oor of the middle fossa. The lesser
wing forms the posterior part of the anterior fossa and the “ridge,”
bordering the anterior part of the middle fossa. The body is pneuma-
tized by the eponymous air sinus and bears the pituitary fossa on its
superior surface.
A number of foramina occur in the skull base, transmitting a variety
of structures and providing potential routes for the spread of extracra-
nial disease (notably infection or tumor) into the vault (Fig. 7.5).
The foramina ovale, rotundum and spinosum are within the greater
wing of the sphenoid bone. The foramina ovale and spinosum are
often symmetrical, the foramen rotundum rarely so.
The foramen rotundum travels from Meckel™s cave to the ptery-
gopalatine fossa and transmits the maxillary (V2) division of the
trigeminal nerve. On coronal CT it is identi¬ed inferior to the anterior
clinoid processes. The foramen ovale transmits the mandibular (V3)
division of the trigeminal nerve. On coronal CT it is identi¬ed inferior
to the posterior clinoid processes (Figs. 7.6, 7.16).
The foramen spinosum is situated posterolateral to the larger
foramen ovale and transmits the middle meningeal artery and vein.
The foramen lacerum contains cartilage and separates the apex of
the petrous bone, the body of the sphenoid, and the occipital bone. It
is crossed by the internal carotid artery.
Anterior clinoid
The squamous portion of the temporal bone forms part of the
Orbital roof process
lateral wall of the middle cranial fossa and its petromastoid consti-
Dorsum sellae
tutes part of the ¬‚oor of the middle and posterior fossae. The occipital
Frontal sinus
Frontal Parietal
Floor of (a) Maxillary antrum
Pineal gland
the anterior
cranial fossa Zygoma

Foramen ovale
Cribriform Foramen spinosum
Foramen lacerum
Sphenoid Calcified
sinus Carotid canal
choroid plexus
Jugular foramen
Lamina dura
of pituitary Normal temporal
fossa bone ˜thinning™
and basisphenoid)

Zygomatic recesses
of the maxillary antra
Mandibular condyle

Fig. 7.4. Continued


ethmoidal bones anteriorly. The inner surface of the skull base is
divided into the anterior, middle, and posterior fossae. The anterior canal
fossa is occupied by the frontal lobe; the middle fossa by the temporal Jugular
lobe. The posterior fossa contains the brainstem and cerebellum.
The orbital plates of the frontal bones form most of the ¬‚oor of the
anterior fossa ¬‚oor with a contribution from the ethmoid bone in the
midline. The inner suface of the frontal bone, forming the ¬‚oor of Fig. 7.5. CT of the skull base: (a) to (c) are contiguous axial images, (a) the most
the anterior cranial fossa, has a relatively “rough” surface, which inferior.

The skull and brain paul butler

(a) (b)
Posterior clinoid
Foramen ovale

Fig. 7.6. Coronal CT of the skull base: (a) is anterior to (b).

bone forms most of the ¬‚oor and walls of the posterior fossa, the
largest of the three.

The skull radiograph
Skull radiograph interpretation
Interpretation of skull radiographs (skull “series”) can be challenging. Vertebral
It is relatively simple to obtain but is an insensitive indicator of artery
intracranial pathology with roles limited to trauma and as a prelimi-
nary to cranial surgery. Of course, CT can largely meet these diagnos-
tic requirements and, if necessary, a digital radiograph can be
obtained as part of the CT examination.
Broadly, when confronted with a frontal radiograph, in the attempt
to interpret the many overlapping and irregular lines and lucencies, it


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