Normal Abdominal Anatomy

Figure 1 Abdominal wall: rectus muscle and sheath. A: Section

obtained immediately caudal to the xiphoid shows the paired rectus

abdominis muscles (ra), which narrow medially to attach to the linea

alba (arrow). They attach laterally to the costal cartilages (arrowheads)

of the fifth through seventh ribs. The fat immediately posterior to them

lies in the root of the ligamentum teres ( lt). L, left hepatic lobe. B:

Section obtained 5 cm caudal to (A). The rectus muscles (ra) have

thinned and broadened. Laterally, they lie on the surface of the

transversus abdominis muscle (arrowheads); medially, the fat in the

root of the ligamentum teres ( lt) apposes their posterior surfaces.

Posterior to that, on the right, is a portion of the greater omentum

(go); on the left is the body of the stomach (ST). L, l iver. C: In this

patient, fatty infiltration of both rectus abdominis muscles (ra) allows

observation of the rectus sheath. At this level (above the arcuate line),

fibers from the transversus abdominis muscle (tr) and, variably, from

the internal oblique muscle (io) pass posterior to the rectus abdominis

muscle to form the aponeurotic posterior rectus sheath (open arrows).

Fibers of the external oblique (eo) and internal oblique muscles blend

together (arrow) to course over the rectus abdominis muscle, forming

the anterior rectus sheath. lt, fat in the root of the ligamentum teres.

Figure 2 Rectus sheath. A: Section obtained above the arcuate line in

a patient with left rectus sheath hematoma (H). Note that the

hematoma is well confined between the aponeurotic fibers of the

external oblique (arrow) anteriorly and the transversus abdominis

(open arrow) posteriorly. B: Section obtained below the arcuate line

shows that only the anterior aponeurosis (arrow) persists. Posteriorly,

the hematoma is unconfined, and extends (curved arrow) into the

extraperitoneal space. Note triangular fat surrounding the urachus (U).

C: Sagittal image in another patient with extensive rectus sheath

hematoma shows that posterior layer of the rectus sheath (arrowheads)

confines the hematoma to the level of the arcuate line. Caudal to this,

the hematoma is free to extend (curved arrow) into the prevesical fat.

Figure 3 Superficial epigastric vessels. A: Section through the pelvic

inlet shows the superficial epigastric vein (arrowhead) within the

subcutaneous fat anterior to the rectus abdominis muscle (RE). This vein

is part of an extensive network that connects to the thoracoepigastric

system, the inferior epigastric system, and the paraumbilical venous

plexus. Just deep to the rectus abdominis muscle is the epigastric artery

(ea) and vein. B: The epigastric vessels (ea) 16 mm inferior to (A) lie

close to the vasa deferentia (arrows) in men (the round ligament occupies

this position in women). Arrowhead, superficial epigastric vein. C: The

epigastric vessels (ea) 16 mm inferior to (B), near their site of origin

from the external i l iac artery and vein, cross the vasa deferentia (arrow).

Nearer the midline is the medial umbilical l igament (ul), the obliterated

remnant of the umbilical artery, coursing anterior to the bladder (BL).

Arrowhead, superficial epigastric vein. D: Coronal view of the anterior

abdominal wall shows the serpentine course of the superficial epigastric

veins (arrows). E: Coronal thick-slab MIP showing the relationship of the

inferior epigastric arteries (1) with major superficial branches of the

external i l iac artery. The inferior epigastric artery arises just above the

inguinal l igament, whereas the superficial circumflex il iac artery (2)

usually arises from the common femoral artery just caudal to the inguinal

l igament. The proximal inferior epigastric artery gives rise to the pubic

artery (3), which courses caudally towards the pubis (P); inferiorly, it

forms an anastamosis with the obturator artery. The common femoral

artery (5) bifurcates into the superficial femoral (6) and deep femoral (7)

arteries. The latter gives rise to a large lateral branch, the lateral

circumflex femoral artery (4). F: Sagittal thick-slab maximum-intensity

projections shows the course of the inferior epigastric artery (arrow) on

the posterior border of the rectus muscle (RM); superiorly, it pierces the

transversalis fascia (open arrow) just below the arcuate line and ascends

between the rectus muscle and its sheath. G: Oblique perspective volume

rendered image shows the origin of the left inferior epigastric artery

(arrow) from the external i l iac artery (ea).

Figure 4 Posterior abdominal wall. A: Section at the level of the renal

hilus shows the bulky erector spinae muscles groups (es) adjacent to the

vertebral transverse process. Overlying the ribs on the posterolateral

surface of the body are the serratus posterior inferior (spi) and latissimus

dorsi (ld) muscles. The latter gives rise to a tough fascial layer, the

thoracolumbar fascia (tlf). B: Section obtained 16 mm caudal to (A). The

superior lumbar space (sls), here containing a small amount of herniated

fat, l ies between the intercostal muscles (ic) and the latissimus dorsi

muscle ( ld) and thoracolumbar fascia (tlf) just lateral to the serratus

posterior inferior (spi) muscle band. es, Erector spinae.

Figure 5 Inferior lumbar triangle (the Petit triangle): normal anatomy.

A: Section through the quadratus lumborum muscle (ql) shows the band-

like latissimus dorsi muscle (ld) covering the posterior aspect of the

posterior abdominal wall, comprised of the transversus abdominis (ta),

internal oblique (io), and external oblique (eo) muscles. The

thoracolumbar fascia (tlf), an extension of the latissimus dorsi muscle,

extends posteromedially to cover the surface of the quadratus lumborum

and erector spinae (es) muscles. B: Section obtained 7 mm caudal to (A)

shows that the latissimus dorsi (ld) muscle has passed posteromedially

with respect to the posterolateral abdominal musculature [transversus

abdominis (ta), internal oblique (io), and external oblique (eo) muscles]

to create a defect, the inferior lumbar space (ils) through which lumbar

hernias can protrude. ql, Quadratus lumborum muscle; es, erector spinae;

tlf, thoracolumbar fascia. C: Coronal reformation in another patient shows

the fat-containing inferior lumbar triangle (asterisk) between the

quadratus lumborum muscle (ql) medially and the thin fibers of the

transversus abdominis muscle (arrow) laterally. D: Oblique coronal

reformation highlights the fat-containing space (asterisk) between the

abdominal wall musculature (chiefly composed of the external oblique

muscle (eo) and the quadratus lumborum muscle (ql).

Figure 6 Traumatic lumbar hernia. A: Axial section obtained above

the il iac crest in a patient involved in high-speed motor vehicle coll ision

while wearing a lap belt. There is marked separation between the

lateral abdominal wall musculature (eo) and the latissimus dorsi muscle

(asterisk), lying just lateral to the quadratus lumborum (ql). B: Coronal

section in the same patient shows herniation of small intestine (curved

arrow) through the traumatic hernia.

Figure 7 Spigelian hernia. Transverse computed tomography section

obtained through the midabdomen shows herniation of greater

omentum (H) through a defect immediately lateral to the rectus

abdominis muscle (RA). This is the classic location for a Spigelian

hernia.

Figure 8 The inguinal canal. A: Axial image obtained in a normal

patient shows the inferior epigastric artery (arrowhead) arising from

the external i l iac (ia) at the level of the internal inguinal ring. The deep

circumflex il iac artery (dci) arises at nearly the same level. B: Axial

image 5 mm inferior to (A) shows the spermatic cord (arrow) entering

the right inguinal canal. C: Axial image 5 mm inferior to (B) shows the

right spermatic cord (arrow) coursing medially within the inguinal

canal, behind fibers of the internal oblique muscle (iom). D: Axial

image 5 mm inferior to (C) shows the spermatic cord (arrow) emerging

from the external inguinal ring to lie just lateral to the rectus

abdominis muscle (ra). E: Oblique coronal reformatted image shows the

inferior epigastric artery (arrowhead) arising from the external i l iac

(ei); the inferior epigastric gives rise to the cremasteric artery (open

arrow) which accompanies the vas deferens (vas) into the inguinal

canal. F: Sagittal image in another subject with a direct inguinal hernia

shows the inferior epigastric artery (arrow) which marks the lateral

boundary of the Hasselbach triangle. The origin of the inferior

epigastric artery and its pubic branch (open arrow) marks the position

of the internal inguinal ring. In this patient, an intestinal loop (i)

protrudes through a defect in the transversalis fascia (arrowheads) to

enter the inguinal canal. G: Sagittal image obtained 10 mm medial to

(E) shows intestinal loop (i) extending toward the fat within the

scrotum (s).

Figure 9 The esophageal hiatus. A: Section obtained immediately

above the gastroesophageal junction shows the right diaphragmatic crus

(rc) adjacent to the fat in the fissure for the ligamentum venosum (flv).

The esophagus (E) passes between the aorta (A) and right crus as it

courses from middle mediastinum into the abdomen. B: Section

obtained 7 mm caudal to (A) shows the abdominal segment of the

esophagus (gej) as it joins the stomach (ST) between the right (rc) and

left (lc) crura. Of incidental note is an accessory left hepatic artery

(alh), arising as a branch of the left gastric artery and coursing through

the fissure for the ligamentum venosum (flv). C: Section obtained 7 mm

caudal to (B) shows approximation of the right crus (rc) to the left (lc),

effectively closing the esophageal hiatus. The left crus of the diaphragm

remains in contact with the anterior surface of the aorta (A). Note that

there has been an increase in the volume of fat within the gastrohepatic

l igament (ghl) adjacent to the lesser curvature of the stomach (ST).

lga, Left gastric artery; gej, gastroesophageal junction. D: Coronal

reformatted image in another patient depicts the esophagus (E)

coursing obliquely from the thorax into the abdominal cavity. Fibers of

the right diaphragmatic crus (rc) sweep to the left to enclose the

esophagus at the hiatus. Arrow, left leaf of the diaphragm; asterisk,

paraesophageal lymph node.

Figure 10 Appearance of anterior leaflets of the diaphragm. A:

Pseudomass caused by anterior diaphragm. In this patient, the central

tendon of the diaphragm is at a level close to the xiphoid process (X).

In this setting, the broad muscles of the anterior diaphragm course in

the same plane as the scan section, producing a pseudomass (M?)

adjacent to the pericardium. B: In this individual, a portion of the

anterior left hemidiaphragm (arrow) is imaged tangentially, simulating

a mass. The fibers comprising the sternal origin of the diaphragm (open

arrow) create a triangular soft tissue density. C: Reformatted sagittal

image near the midline shows the fibers originating from the sternum,

and extending posteriorly to join the central tendon (arrowheads).

Figure 11 Diaphragmatic muscle mimicking liver lesion. A: Computed

tomography section obtained at a level inferior to the dome of the

diaphragm shows a peripheral band-like low-attenuation defect (arrow).

B: Magnetic resonance imaging section in the same location shows a low-

intensity structure (arrow) at the liver periphery. Serial images

demonstrated its association with a rib.

Figure 12 Splenic indentation from diaphragmatic slip. A: Section near

the gastroesophageal junction shows a fat-containing notch (arrow) on

the posterolateral aspect of the spleen (S). A, Aorta; ST, stomach; L,

l iver. B: Section obtained 5 mm inferior to (A) shows the soft tissue

attenuation diaphragmatic slip passing through the splenic notch as it

becomes continuous with the diaphragm. S, Spleen; A, aorta; ST,

stomach; L, l iver.

Figure 13 Median arcuate ligament. A: Axial section obtained just above

the celiac trunk shows the median arcuate ligament (arrow) immediately

anterior to the aorta, extending between the left (lc) and right crus (rc).

B: Reformatted sagittal image obtained at end expiration shows the

proximity of the celiac trunk (ct) with the median arcuate ligament

(arrow). In some patients, end-expiratory imaging produces apparent

occlusion of the proximal celiac artery.

Figure 14 Retrocrural space. A: Section obtained at the

gastroesophageal junction shows the abdominal segment of the esophagus

(E) passing obliquely through the hiatus between the right (rc) and left

crura (lc). The retrocrural space defined by the crural fibers is a

continuation of the mediastinum. It contains the aorta (A); the azygous

(az) vein, which on this section receives an intercostal vein (arrow); the

hemiazygous (haz) vein; a variable amount of fat; the thoracic duct and

lymph nodes (arrowhead); and part of the sympathetic trunk. At this level

and the next, there is continuity between the retrocrural space and the

abdominal contents, namely, the esophagus and gastrohepatic ligament

(ghl). B: Section obtained 16 mm below (A). The left (lc) and right crura

(rc) have reapposed below the esophageal hiatus. A small bulbous

projection from the right crus (open arrow) projects into the region of the

gastrohepatic l igament; this can mimic a node if its continuity with the

remainder of the crus is not appreciated.

Figure 15 Cisterna chyli. A: T2-weighted magnetic resonance axial

image through the thoracolumbar junction shows a large fluid-fil led

structure (C) just to the right of the aorta (A) and immediately anterior to

the hemiazygos vein (arrow). B: Sagittal image in the same subject shows

the junction of the dilated right lumbar trunk (arrowhead) with the

cisterna chyli (C).

Figure 16 Lateral arcuate ligament. A–D: Serial sections beginning

just inferior to the renal hilus show the lateral arcuate ligament (arrow)

extending from a lateral position near its attachment to the rib (in [A]) to

a more posterior position immediately behind the right kidney (RK) (in

[D]). On the inferior segments, the ligament is thicker and broader than

at its attachment, and mimics a mass. L, Liver.

Figure 17 Traumatic rupture of the diaphragm. A: Axial section through

the lower thorax in a patient involved in a motor vehicle coll ision shows a

large left pneumothorax (Ptx). The fundus of the stomach (ST) lies

occupies the posterior hemithorax at this level. B: Reformatted coronal

image in the same patient shows large gap (between arrows) in the left

hemidiaphragm, with protrusion of the gastric fundus (curved arrow) into

the thorax through the defect. ST, stomach.

Figure 18 Mesenteries attached to the stomach and the developing

intramesenteric viscera. Adapted from reference 74. A: Schematic

drawing of a section obtained in an embryo, near the end of the fifth

week of development. The stomach (ST) is supported by two major

mesenteries, ventral and dorsal. Developing within the ventral mesentery,

and distorting its surface, the liver (L) grows chiefly into the right

peritoneal space (RPS). Maternal blood courses through the ventral part

of the ventral mesentery, which becomes the falciform ligament (1). The

dorsal portion of this ventral mesentery (2) contains the left gastric

artery and coronary vein and, more caudally, the hepatic artery, portal

vein, and biliary duct within its leaves. This mesentery will become the

lesser omentum. The spleen (S) takes shape in the ventral part of the

dorsal mesentery; the gastrosplenic ligament (3) formed from it carries

the short gastric vessels. Although the head of the pancreas (P) arises in

the dorsal mesoduodenum, its tail grows in a cephalic direction to occupy

the dorsal mesogastrium within the splenorenal ligament (4); (A) aorta;

(K) kidney; (V) vertebral body; (LPS) left peritoneal space. B:

Approximately 1 week later, the rapid hepatic growth forces considerable

rotation of the stomach (ST) and attached lesser omentum (2).

Meanwhile, the pancreatic tail (P) has fused to the dorsal body wall,

reducing the posteromedial extent of the left peritoneal cavity (LPS). This

line of fusion generally continues along the splenorenal l igament to form

a posteromedial splenic “bare†or nonperitonealized area. In some

patients, this fusion does not occur, and peritoneum extends behind the

posterior pancreatic tail. In this condition, the spleen is on a mesentery

of variable length and can “wander†within the peritoneal cavity; 1,

falciform ligament; 3, gastrosplenic l igament; 4, splenorenal l igament; A,

aorta; K, kidney; V, vertebral body; L, l iver; S, spleen.

Figure 19 The gastrohepatic and hepatoduodenal ligaments. A: The

gastrohepatic l igament extends between the lesser curvature of the

stomach (ST) and the fissure for the ligamantum venosum (between

arrows). It contains branches of the left gastric artery and coronary

veins. B: Axial section obtained 20 mm inferior to (A) shows the course

of the left gastric artery (lga) through the fat-containing gastrohepatic

l igament (ghl). Just anterior to the caudate lobe (CL) is a slightly

enlarged lymph node (open arrow). C: Reformatted volume rendered

image shows the structures of the lesser omentum. The lower portion

(hepatoduodenal ligament) contains the portal vein (pv), common

hepatic duct (chd) and hepatic artery (black arrowhead). A small

hepatic chain lymph node is present (white arrowhead). To the left and

superiorly, the gastrohepatic l igament (ghl) contains the left gastric

artery (lga). Note drainage (open arrow) of the coronary vein into the

portal vein near the splenoportal confluence. A portion (called the tuber

omentale) of the body of the pancreas (p) protrudes into the

gastrohepatic ligament. 2d, Descending duodenum; 4d, fourth portion

of the duodenum; H, pancreatic head.

Figure 20 Formation of the gastrocolic l igament. Adapted from

reference 74. A: Schematic drawing of a sagittal section through a

developing embryo. Growth of the right peritoneal space (RPS) behind

the stomach (ST) has greatly elongated the gastrosplenic l igament

(GSL), so that it hangs like a drape over the transverse colon (TC) and

its attached dorsal mesentery (dm); P, pancreas; d, duodenum; J,

jejunum. B: Fusion occurs between anterior and posterior surfaces of

the gastrosplenic ligament, obliterating part of the right peritoneal

space (RPS) and forming the gastrocolic l igament (gcl). The posterior

surface of the fused ligament in turn fuses to the transverse colon (TC)

and its dorsal mesentery to form the adult transverse mesocolon (tmc);

P, pancreas; d, duodenum; J, jejunum; ST, stomach.

Figure 21 The gastrosplenic ligament. A: Computed tomography section

through the upper abdomen in a patent with ascites shows fluid-fil led

peritoneal spaces outlining the gastrosplenic l igament (gsl). The

gastrosplenic l igament is the fat-containing structure between the left

anterior subphrenic space (LAS) and the inferior recess of the lesser sac

(ls). The serpentine structures within this fat are the short gastric

arteries, which arise from the splenic artery and supply the greater

curvature of the stomach (ST). Embryologically, the gastrosplenic

l igament forms part of the transverse mesocolon and all of the greater

omentum. S, spleen. B: Fluid in the gastrosplenic l igament. In this

patient with pancreatitis, a large fluid collection (F) within the

gastrosplenic l igament distorts the posterolateral wall of the stomach

(ST).

Figure 22 The greater omentum. A: Axial section in a patient with

widespread peritoneal metastases shows extensive soft tissue involvement

of the greater omentum (GO). Omental fat (arrow) and gastroepiploic

vessels (arrowhead) persist. B: Sagittal image in the same patient

demonstrates the cephalocaudal extent of the omentum (GO) and the

gastroepiploic vessels (arrowhead) coursing within the small amount of

preserved omental fat.

Figure 23 The transverse mesocolon. A: Volumetric axial reformatted

image through the midabdomen shows the middle colic artery (mca)

arising from the superior mesenteric artery (sma) and branching within

the transverse mesocolon to supply the transverse colon (TC). Tributaries

of the middle colic vein (arrows) here drain directly into the superior

mesenteric vein (smv). P, pancreatic head and uncinate process. B:

Coronal reformatted image in the same patient shows the transverse

mesocolon spanning the entire upper abdomen. The middle colic veins

(arrows) mark the position of the mesocolon, which lies immediately

superior to the pancreas (P) and inferior to the stomach (ST).

Figure 24 The bare area of the spleen. A: The left posterior subphrenic

(perisplenic) space (LPS) nearly encircles the spleen (SP). A portion

(arrows) of its posterior surface, adjacent to the left kidney (LK) is non-

peritonealized; it is part of the splenorenal l igament, which fused to

become part of the retroperitoneum. B: In this patient, retroperitoneal

gas (asterisk) from a duodenal perforation outlines the bare area of the

spleen (SP). LK, left kidney; lad, left adrenal gland.

Figure 25 Embryologic growth and rotation of the colon. A: Line

drawing of the fetal abdominal cavity prior to colonic rotation. The

colon begins as a relatively straight tube supported by the dorsal

mesentery (DM). At this point in embryologic development, the

posterior body surface is comprised of the anterior surfaces of the

kidneys and the perirenal fat that surrounds them. LK, left kidney; RK,

right kidney; P, pancreas; DC, descending colon; AC, ascending colon.

B: After considerable elongation, the colon rotates so that the

ascending colon (AC) undergoes a 180-degree rotation and then

“flops†to the right on its dorsal mesentery. In this way, the

original left surface of that mesentery fuses with the anterior portion of

the right perirenal space in front of the right kidney (RK). In similar

fashion, the descending colon (DC) and its dorsal mesentery swings to

the left, so that its left surface fuses in front of the left kidney (LK)

and perirenal space. These fusions produce symmetric retromesenteric

planes inferior to the transverse colon (TC). The dorsal mesentery (DM)

of the transverse colon does not fuse posteriorly; its left surface faces

anteriorly. P, pancreas; SC, sigmoid colon. C: The elongated

gastrosplenic ligament hangs like a drape in the front of the abdominal

cavity, where it forms the greater omentum (go). Its posterior surface

fuses with the dorsal mesentery of the transverse colon (TC) to form

the transverse mesocolon (TMC). ST, stomach; P, pancreas.

Figure 26 Peritoneal spaces of the upper abdomen. On these schematic

drawings, the left peritoneal spaces are drawn with heavy black lines, and

the right peritoneal spaces have vertical hatching. A: Near the

gastroesophageal junction, four divisions of the left peritoneal space are

present. Anterior to the liver, medially l imited by the falciform ligament

(curved arrow) is the left anterior perihepatic space (1). Curving posterior

to cover the visceral hepatic surface is the left posterior perihepatic space

(2). The anterior subphrenic space (3) separates the gastric fundus (ST)

from the diaphragm, and the posterior subphrenic space (4) (also called

the persplenic space) surrounds the spleen. The right peritoneal space

consists of two perihepatic spaces and two portions of the lesser sac. The

perihepatic spaces consist of a broad diaphragmatic surface (5), l imited

on the left by the falciform ligament (curved arrow) and posteromedially

by the bare area (straight arrow marks the peritoneal reflection). The

second part of the right perihepatic space, the hepatorenal fossa, is

present on more caudal sections. The lesser sac consists of a superior

recess (6) surrounding the caudate lobe (CL) and an inferior recess (7)

that lies posterior to the stomach. The two are anatomically continuous

structures, but the gastrohepatic fold is interposed between them on

cephalic sections; L, l iver; e, esophagus; V, vertebral body. B: Two cm

caudal, the superior recess of the lesser sac (6) surrounds the caudate

lobe on three sides. The peritoneal reflection at the hepatic bare area

(straight arrow) is more posterior and medial than on the previous

section; (curved arrow) falciform ligament; (ST) stomach; (S) spleen; (P)

pancreas; (LK) left kidney; (V) vertebral body; (L) liver. C: Two cm

caudal, the posterior subphrenic (perisplenic) space is l imited inferiorly

by the phrenicocolic l igament (arrowhead) formed when the proximal

descending colon (DC) and its attached dorsal mesentery fuses to the

posterior body wall and to the lateral margin of the diaphragm. At this

level, the posterior left perihepatic space (2) extends deep into the

visceral surface of the liver, near the left portal vein (LPV). The superior

recess of the lesser sac surrounds the papillary process (pp) and caudate

process (cp), which together comprise the caudate lobe of the liver. The

cephalic portion of the visceral right perihepatic peritoneum (8) is l imited

laterally by the triangular ligament (straight arrow); L, l iver; curved

arrow, falciform ligament; ST, stomach; DJ, duodenojejunal flexure; P,

pancreas; RK, right kidney; LK, left kidney; V, vertebral body. D: Four cm

caudal, the left posterior perihepatic space (2) contacts the anterior wall

of the gallbladder (gb). The inferior recess of the lesser sac (7) extends

into the leaves of the greater omentum (GO), which lies anterior to the

distal transverse colon (TC). The visceral right perihepatic space (also

known as the hepatorenal space or the Morison pouch) extends between

the visceral surface of the liver and the right kidney (RK); it is

continuous, by way of the foramen of Winslow, with the superior recess of

the lesser sac; L, l iver; curved arrow falciform ligament; LK, left kidney;

V, vertebral body; J, jejunum; ST, stomach; d, duodenum; DC,

descending colon.

Figure 27 Left peritoneal spaces. A: Axial section through the upper

abdomen in this patient with diffuse ascites shows fluid in the left

anterior subphrenic (LAS) space, producing posterior displacement of the

stomach (ST) and greater omentum (GO) from the left hemidiaphragm.

There is a small amount of f luid in the left anterior perihepatic space

(LAP), circumscribed on the right by the falciform ligament (arrow). B:

Axial section 3 cm inferior to (A) shows posterior extension of the left

posterior perihepatic space (LPP), lying between the stomach (ST) and the

lateral segment of the left hepatic lobe (L). The perisplenic space (LPS) is

separated from the fluid in the inferior recess of the lesser sac (LS) by

the transverse mesocolon (TMC). C: Axial section 2 cm inferior to (B)

shows the left posterior perihepatic space (LPP) separated from the

inferior recess of the lesser sac (LS) by the gastrohepatic l igament (ghl).

The transverse mesocolon (TMC) forms the lateral wall of the lesser sac,

separating it from the left posterior subphrenic space (LPS) around the

spleen.

Figure 28 The phrenicocolic l igament. Coronal reformatted image

from the patient il lustrated in Fig. 10-27 shows the continuity of the

left posterior perihepatic space (LPP) with the left anterior subphrenic

space (LAS) and left posterior subphrenic space (LPS). The transverse

mesocolon (TMC) separates the perisplenic space from the inferior

recess of the lesser sac (LS) behind the stomach (ST). Just inferior to

the spleen (SP), the lateral extension of the transverse mesocolon,

called the phrenicocolic ligament (PCL), attaches to the left

hemidiaphragm (arrow).

Figure 29 Right peritoneal spaces. Oblique coronal reformatted image

shows a large fluid collection in the right subphrenic space (RS), which

is l imited superiorly by the falciform ligament (arrow). This continues

posteroinferiorly with the hepatorenal space (HRS), also known as the

Morison pouch. That, in turn, communicates through the foramen of

Winslow with the superior recess of the lesser sac (SR) adjacent to the

caudate lobe (CL) of the liver. From there, it extends posteroinferiorly

into the inferior recess of the lesser sac (IR) inferior to the stomach

(ST). At this level, the gastrohepatic l igament (ghl) protrudes into the

lesser sac.

Figure 30 The Morison pouch and the bare area. Right peritoneal space

collections. Patient with intraperitoneal rupture of the urinary bladder,

who underwent computed tomography cystography; dilute iodinated

contrast material has fi l led the right peritoneal spaces. A: Section

through the inferior portion of the porta hepatis. Dilute contrast fi l ls the

right perihepatic space (rp), separated on this section from the

hepatorenal fossa (hr) by the caudal margin of the bare area of the liver

(arrow). Some of the contrast in the hepatorenal fossa has extended

anteriorly to surround the caudate lobe of the liver (L), outlining the

superior recess of the lesser sac (sr). Note the position of this contrast

between the portal vein (PV) and the inferior vena cava (C). At this level,

the left gastric fold at the root of the gastrohepatic ligament (gh)

separates the superior recess from the inferior recess (ir), which lies

behind the fluid-fil led stomach (ST). B: Section obtained 8 mm caudal to

(A). Communication between the hepatorenal fossa (hr) and the superior

recess of the lesser sac (sr) by way of the foramen of Winslow (fW) is

clearly depicted on this section. A, aorta; ST, stomach; D, duodenum; PV,

portal vein; ir, inferior recess of the lesser sac. C: Axial magnetic

resonance image in another patient with ascites. The triangular ligament

(arrow) is outlined by hyperintense ascitic f luid in the right perihepatic

(subphrenic) space (ph) and in the hepatorenal fossa (hr), or the Morison

pouch. RK, right kidney; L, l iver.

Figure 31 Superior recess of the lesser sac. Peritoneal fluid

collections. Patient recovering from bil iary surgery complicated by bile

leakage. Section through the liver (L) just above the porta hepatis

shows a large peritoneal f luid collection (LP) in the left posterior

perihepatic space. It is separated from a smaller collection (SR) in the

superior recess of the lesser sac by the gastrohepatic l igament. A,

aorta; ST, stomach; S, spleen.

Figure 32 Extension of fluid between leaves of greater omentum. A:

Axial section in a patient with gastric perforation into left peritoneal

space and the lesser sac. Air and contrast is present in the left anterior

(LAP) and left posterior (LPP) perihepatic spaces. Another denser

collection is separated from those spaces and from the left

hemidiaphragm (arrow) by a fatty band containing gastroepiploic vessels

(arrowheads). B: Axial section 2 cm inferior to (A) shows air and contrast

in the inferior recess of the lesser sac (IR), which extends (curved arrow)

between the leaves of the greater omentum (curved arrow).

Figure 33 Great vessel space. A: Axial section shows the contents of

the upper portion of the great vessel space, which lies between the two

perinephric spaces. On the right, the inferior vena cava (IVC) marks

the posterior boundary of the space; just medial to it, within the

perivascular fat, is the inferior phrenic artery (arrowhead) and the

celiac neural plexus (not visible, but reliably present at this level). B:

Coronal section through the posterior aspect of the great vessel space

shows the renal arteries (arrows) extending into the perirenal fat to

supply the kidneys. This provides continuity between the great vessel

space and the perirenal fat. *, Fat in great vessel space. C: Coronal

section 2 cm anterior to (B) shows the course of the left renal vein

(lrv), receiving tributaries from the gonadal vein (gv) and left adrenal

vein (lav) as it crosses anterior to the aorta to drain into the inferior

vena cava (IVC). The shorter right renal vein (rrv) has a more vertical

course and does not typically receive a gonadal tributary. D: Oblique

volumetric perspective rendering shows the aorta and its major

branches: the celiac trunk (ct), superior mesenteric artery (sma), renal

arteries (arrows) and the inferior mesenteric artery (ima). A portion of

the left renal vein (lrv) is seen crossing anterior to the aorta.

Figure 34 Early retroperitoneal f ibrosis affecting contents of the

great vessel space. A: Axial MR inferior to the renal hila shows high-

intensity inflammatory tissue surrounding the aorta (A), and extending

behind the inferior vena cava (IVC), but not involving either perinephric

space. B: Section obtained 2 cm inferior to (A) shows the process to be

confined to the space surrounding the aorta (A) and inferior vena cava

(IVC). It is l imited anteriorly by the root of the intestinal mesentery

(rm) and posteriorly by the vertebral body (V) and psoas muscles.

Laterally, it extends to the medial boundary of the ureters (U). C:

Section obtained just above the aortic bifurcation shows the inferior

extent of this process, which surrounds both great vessels and extends

laterally to the medial boundary of the ureters (U). D: Coronal section

through the upper abdomen shows the cephalocaudal extent of this

inflammatory process within the great vessel space.

Figure 35 Extension of aortic rupture. Retrorenal plane. Section just

inferior to the hila of the kidneys, in a patient who has undergone

previous aortic graft surgery, shows a large aortic aneurysm (A), from

which blood has leaked into a well-demarcated plane lying between the

posterior pararenal fat (pp) and the perirenal fat (pr). The volume of

this collection (rr) has produced displacement of the left kidney (LK) as

well as structures within the anterior pararenal space: the pancreatic

tail (P) and the spleen (S). This retrorenal plane is continuous with the

inferior diaphragmatic fascia.

Figure 36 Psoas spaces. A: Axial magnetic resonance section just

below the aortic bifurcation shows the psoas muscle (PS) separated

from the vertebral body (V) by strands of fat within which course roots

of the lumbar plexus (arrow) and the lumbar veins (arrowheads).

Laterally, the psoas muscle is separated from the quadratus lumborum

muscle by a fat plane that contains the lateral femoral cutaneous

nerve. B: At the level of the il iac crest, the psoas muscle is divided by

the fat-containing psoas tendon (open arrows). In this groove are the

femoral nerve (fn) and, more medially, the obturator nerve (on). The

fibers of the il iacus muscle (im) are beginning to appear on the right.

lv, Lumbar vein. C: Coronally reconstructed computed tomography

shows the origin of the psoas muscle (arrows) from the transverse

processes of the upper vertebrae, and its intra-abdominal extent. In

the pelvis, it joins with the il iacus muscle (im) to become the il iopsoas,

to insert inferiorly on the lesser trochanter of the femur. D: Thick-slab

volumetric rendering shows the lumbar arteries (arrows) coursing

between the vertebral body and the psoas muscles within the psoas

space.

Figure 37 Neurofibromatosis type I and the psoas muscle. A: Axial

section through lower abdomen shows deformity of the medial aspect of

both psoas muscles (pm) by a plexiform neurofibroma involving the

lumbar nerve (arrows). There is a neurofibroma in a lateral cutaneous

spinal nerve within the left erector spinae muscle (open arrow). B:

Section through the upper pelvis shows enlargement of the sacral nerve

roots (arrowheads). Neurofibromas enlarge the lumbar plexus (lp), the

genitofemoral nerve (gf) and the femoral nerve (f). C: Section through

the pelvis shows involvement of the right sciatic nerve (SC) and both

obturator nerves (ob). There is symmetrical enlargement of the

splanchnic nerves (spl) that course within the mesorectal fascia.

Figure 38 Fascial planes around the kidney in a normal subject. A:

Thick slab axial volume shows the typically thin anterior renal fascia

(arrow) behind the descending colon mesentery (asterisk). The fusion

plane between the descending colon (dc) and the posterior pararenal

fat (pf) is the lateroconal fascia (open arrow). These two fascial planes

are continuous with the posterior renal fascia (arrowheads). B: Thick-

slab axial volume approximately 2 cm inferior to (A) shows increased

volume of fat on the posterolateral aspect of the perirenal space. The

posterior renal fascia (arrowheads), on the inner surface of the

posterior pararenal space (pf) extends between the descending colon

(dc) and the quadratus lumborum muscle (ql). C: Sagittal reformatted

image in the same subject shows the conical shape of the perirenal fat.

The anterior renal fascia (arrows) meets the posterior renal fascia

(arrowheads) at the apex of the cone and continues inferiorly into the

pelvis along the surface of the psoas muscle (PM).

Figure 39 Dissection of f luid into expandable fascial planes. A: Axial

section from a cadaver in which yellow latex was injected into the

parenchyma of the pancreas. In all the cadavers studied, the latex was

confined to an expandable plane (rmp), the retromesenteric plane, that

is situated anterior to the perirenal fat (per), containing the adrenal

(ad), and the tail of the pancreas (p). B: Axial section from a patient

with mesenteric trauma shows blood in the retromesenteric plane (rmp)

behind the descending colon mesentery (asterisk) and the perirenal fat

(per). ad, Left adrenal gland. C: Sagittal section in the same patient as

(B) shows the retromesenteric plane (rmp) anterior to the conical

perirenal fat (per). The posterior renal fascia (arrowheads) joins the

retromesenteric plane at the apex of the cone of perirenal fat and

continues inferiorly (open arrows) along the left psoas muscle (PM). D:

Axial section from a patient with pancreatitis shows a collection of fluid

expanding the posterior renal fascia (arrowheads) in the retrorenal

plane (rrp). The collection abuts and distorts the left psoas muscle

(PM). E: Sagittal section in the same patient shows the cephalocaudal

extent of the retrorenal plane (rrp). The collection extends superiorly

to expand the inferior diaphragmatic fascia (open arrows). F:

Dissection performed in another cadaver in which blue latex was

injected into the pancreatic parenchyma. After incision of the white line

of Toldt, which marks the fusion of the dorsal mesentery of the colon

with the posterior pararenal fat, the colon can be reflected on its

mesentery to reveal the latex (rmp) within the retromesenteric plane

anterior to the perirenal fat (per). In this cadaver, some of the latex

extended posteriorly into the retrorenal plane (rrp) posterior to the

perirenal fat. G: Axial section in a patient with pancreatitis shows

retromesenteric fluid (rmp) extending posterior to the descending colon

(dc) to enter the continuous retrorenal plane (rrp).

Figure 40 Fluid in retromesenteric plane crosses the midline. Section

through the root of the mesentery in a patient with hemorrhagic

pancreatitis shows a large hemorrhage (rm) occupying the

retromesenteric plane. The hemorrhage resulted from rupture of a

pseudoaneurysm (arrowhead). The collection extends posterior to the

pancreas (P) and the root of the mesentery, which contains the

superior mesenteric artery (arrow) and vein (smv). It l ies anterior to

the inferior vena cava (C), aorta (A), and left renal vein (lrv). This is

the characteristic location in which retroperitoneal collections cross the

midline.

Figure 41 Septa within the perirenal fat. A: Axial section from a

cadaver in which blue latex has been injected into the renal parenchyma.

There is extensive accumulation of the latex in the perirenal fat, some of

which courses through a renofascial septations to enter the retrorenal

plane (rrp). The presence of these septa was first noted by Kunin (73). A:

Axial magnetic resonance section in a patient who had had previous

episodes of hydronephrosis shows laminar septa within the perirenal fat.

Renorenal septa (arrows) course between one part of the renal capsule

and another, while renofascial septa conduct fluid to the expandable

fascial planes surrounding the perirenal fat, in this example the retrorenal

plane (rrp).

Figure 42 Pancreatitis affecting the kidney. A: Axial image in a patient

with acute pancreatitis shows fluid in the gastrosplenic ligament (gsl) and

retromesenteric plane (rmp). Fluid courses through the renofascial septa

to gain access to the renal capsule (arrow). A: Two months later, there is

a pseudocyst (psu) confined to the perirenal space adjacent to the renal

capsule by renorenal septa. B: Coronal reformatted image shows the

extensive pancreatic pseudocyst (psu) distorting the renal parenchyma

due to its confinement by renorenal septa.

Figure 43 Gastric diverticulum simulating adrenal mass. A: Section

through the upper abdomen in a patient being staged for lung cancer

shows a round, low-attenuation mass (ad?) posterior to the stomach (ST)

and just medial to the spleen (S). This was felt to be an adrenal

adenoma. B: After administration of oral contrast material, both the

stomach (ST) and the questionable adrenal mass (tic) f i l l with barium

suspension, confirming that the apparent mass is in fact a gastric

diverticulum. This is the characteristic location for this common

congenital anomaly.

Figure 44 The posterior pararenal space. A: Axial section through the

lower abdomen shows the lenticular fat collection within the posterior

pararenal space (pps), delimited on its inner surface by the posterior

renal (prf) and lateroconal (lcf) fasciae, and on its outer surface by the

transversalis fascia (arrow). No organs are present within this fat,

although the il ioinguinal and lateral femoral cutaneous nerves pass

through this space. B: Coronal reformatted image from the same

individual shows the extent of the posterior pararenal fat (pps), which

extends from the diaphragm to the pelvis.

Figure 45 Escape through the Petit triangle. Axial image in this

patient who sustained a duodenal perforation during endoscopic

retrograde cholangiopancreatography shows extensive fluid in the

retromesenteric plane (rmp). Between the posterior pararenal fat (pps)

and the fat anterior to the quadratus lumborum muscle (qlf) is a plane

(pt) through which fluid escapes to gain access to the transversalis

fascia (arrows). This is at the level of the inferior lumbar triangle, and

is a common means for fluid in the deep retroperitoneum to be diverted

to the flank. Its existence explains the Grey Turner sign of hemorrhagic

pancreatitis.

Figure 46 Subperitoneal spread of pancreatitis to gastrosplenic

l igament. A: Axial section through the tail of the pancreas shows fluid

within the retromesenteric plane (rmp) between the pancreatic tail (P)

and the perirenal space (per). Some fluid (fl) has extended to the renal

capsule through the renofascial septa. B: Axial section obtained 3 cm

superior to (A) shows extension of fluid into the gastrosplenic ligament,

here identified because of the short gastric arteries (arrowheads) that

course within it.