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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.