DOI:10.2214/AJR.05.1156
AJR 2006; 186:S452-S455
© American Roentgen Ray Society
AJR Teaching File: Acute Abdominal Pain After Combined Kidney and Pancreas Transplantation
Frederick Chen1 and
Alvin C. Silva1
1 Both authors: Department of Diagnostic Radiology, Mayo Clinic Scottsdale,
13400 E Shea Blvd., Scottsdale, AZ 85259.
Received July 8, 2005;
accepted after revision September 18, 2005.
Address correspondence to A. C. Silva
(silva.alvin{at}mayo.edu).
Keywords: abdominal imaging • anatomy • gastrointestinal radiology • infarction • ischemia • omentum
Clinical History
One week after receiving a combined kidney and pancreas transplant, a
39-year-old man presented with acute abdominal pain and a low-grade fever.
Radiologic Description
Unenhanced axial and coronal CT images (Figs.
1A,
1B, and
1C) show streaky infiltration
of the omentum involving the left abdomen cephalad to the left lower quadrant
renal transplant. The left colon is not well distended, but the immediately
adjacent colon wall is not abnormally thickened. A comparison CT scan in
another patient with epiploic appendagitis
(Fig. 2) shows the
characteristic hyperattenuating rim of this process, which is not found in
omental infarction. An additional comparison CT scan in yet another patient
(Fig. 3) shows the
discriminating feature of colon wall thickening, which is associated with
acute diverticulitis but not seen in omental infarction.
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Fig. 1A —39-year-old man with omental infarction who presented with acute
abdominal pain and low-grade fever 1 week after receiving combined kidney and
pancreas transplant. Axial unenhanced CT scan shows thickening and
infiltration of omentum (arrow) anterior and lateral to descending
colon (arrowhead). Note lack of thickening in adjacent colon
wall.
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Fig. 1B —39-year-old man with omental infarction who presented with acute
abdominal pain and low-grade fever 1 week after receiving combined kidney and
pancreas transplant. Axial unenhanced CT scan caudal to A shows
significantly more infiltration of omentum (arrow).
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Fig. 1C —39-year-old man with omental infarction who presented with acute
abdominal pain and low-grade fever 1 week after receiving combined kidney and
pancreas transplant. Coronal unenhanced CT scan shows extension of abnormal
omentum (long arrows) from level of splenic flexure of colon
(arrowhead) to above level of renal transplant (short
arrow). Note associated mass effect displacing colon to the right.
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Fig. 2 —72-year-old afebrile woman with epiploic appendagitis who presented
with acute left lower quadrant pain and laboratory values within normal
ranges. Axial contrast-enhanced CT scan at level of junction of descending and
sigmoid colon shows oval paracolonic fatty mass with hyperattenuating rim
(arrow) that is characteristic of epiploic appendagitis, despite
presence of diverticula (arrowheads). In addition, this patient's
clinical presentation is not typical of someone with diverticulitis. In a
patient with no prior surgery, location and appearance would also preclude
segmental omental infarction.
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Fig. 3 —67-year-old febrile man with acute diverticulitis who presented with
left lower quadrant pain, leukocytosis, and known history of diverticulosis.
Axial contrast-enhanced CT scan at level of distal descending colon shows
abnormal infiltration of pericolonic fat and associated punctate gas
collections (long arrow). Note abnormal thickening of colon wall
(short arrow) adjacent to pericolonic inflammatory changes.
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Differential Diagnosis
The differential diagnosis in this patient includes acute diverticulitis,
primary epiploic appendagitis, segmental omental infarction, and metastatic
disease.
Diagnosis
The diagnosis in this patient is segmental omental infarction.
Commentary
Abnormal thickening and infiltration of the omentum are nonspecific
findings. The differential diagnosis ranges from acute, focal, and diffuse
infectious causes (appendicitis, diverticulitis, and peritonitis), to vascular
causes (omental infarct and epiploic appendagitis), to chronic processes
(carcinomatosis, mesothelioma, lymphoma, and tuberculosis)
[1,
2]. In most cases of omental
thickening, the patient's history can help narrow this differential diagnosis.
For example, patients with peritoneal spread of cancer may present with either
a known history of carcinoma or chronic nonspecific abdominal symptoms and
weight loss but with no other significant symptoms. On CT, carcinomatosis will
typically show irregular nodular peritoneal thickening, soft-tissue masses,
and ascites [3].
In the acute clinical setting, infection and infarct should be considered.
These entities can usually be characterized by their typical appearance on CT
[4]. Segmental omental
infarction is a rare entity; affected patients clinically present with acute
abdominal pain and minimal, if any, other symptoms or abnormal laboratory
values [5]. CT is the study of
choice to evaluate patients for omental infarction because it can exclude the
more common causes of an acute abdomen, such as diverticulitis or
appendicitis, that can result in similar clinical symptoms. CT findings of
infarction include omental infiltration with or without a fatty mesenteric
mass
[6-8].
In some cases, a whirling appearance of the mesentery may also be observed.
With conservative management, the patient's symptoms should generally resolve
within 2 weeks [4].
The greater omentum is a fat-laden double layer of peritoneum that extends
from the stomach to the transverse colon, then drapes over the intraabdominal
contents anteroinferiorly. Although perfused by numerous small vessels, the
omentum has a vascular supply that is relatively less redundant than that of
the small or large bowel because fewer collaterals are present
[9]. Although the exact
pathogenesis of acute segmental omental infarction is not known, it is thought
to be the result of an anomalous blood supply, particularly to the right lower
quadrant of the omentum, with mechanical factors inducing venous thrombosis
[4,
5]. Thus, as a general rule,
segmental omental infarcts occur in the right abdomen. Accepted predisposing
factors include venous kinking due to increased abdominal pressure,
compression of the omentum between the liver and the anterior abdominal wall,
various causes of vascular congestion (postprandial causes, particularly in
obese patients, coughing, Valsalva maneuver; and right-sided heart failure),
and recent surgery
[1-3,
8].
Other possibilities in the differential diagnosis can be excluded for the
following reasons: Acute diverticulitis will classically present with left
lower quadrant pain and associated fever or leukocytosis. In addition to
symptoms, the discriminating CT findings
(Fig. 3) include abnormal
thickening of the colon wall, which is typically not present with epiploic
appendagitis or segmental omental infarction, and the presence of diverticula.
Location is often a helpful clue because segmental omental infarction is
generally right-sided except in postsurgical patients, in whom altered local
omental vascularity may be the precipitating factor, as in our patient.
Primary epiploic appendagitis is the sequela of infarction of one of the
fatty appendages projecting from the colon. If it occurs on the right side,
the clinical presentation can mimic segmental omental infarction (abdominal
pain with little or no associated fever or leukocytosis). However, the CT
findings are usually diagnostic for this entity, showing an oval paracolonic
fatty mass with a hyperattenuating peripheral ring of inflamed peritoneal
lining [10]
(Fig. 2). In addition, there
typically is no associated mass effect on the adjacent colon, as can be seen
with omental infarction (Figs.
1A,
1B, and
1C).
Metastatic disease can be excluded from the diagnosis because there is no
history of, nor any preoperative findings of, a primary neoplasm. There are no
solid peritoneal soft-tissue masses, and the free fluid is due to recent
surgery because it was not present on preoperative evaluation. Thus, given our
patient's clinical situation of a recent complicated surgery, segmental
omental infarction would be the most likely diagnosis.
Take-home pearl: Segmental omental infarction is a rare, self-limited
process with a clinical presentation of acute abdominal pain.
Segmental omental infarction is a right-sided process unless it is found
after surgery; it can be differentiated from primary epiploic appendagitis
because it is larger, can have mass effect on the adjacent colon, and lacks a
hyperattenuating ring of inflamed peritoneal lining. It can be differentiated
from classic diverticulitis because of its abdominal location, the patient's
clinical presentation, and its lack of associated thickening of the colon
wall.
Objective
The educational objective of this teaching article is to describe the
typical findings on CT of segmental omental infarction, a rare, self-limited
process.
Conclusion
Segmental omental infarction is an uncommon cause of abdominal pain that,
clinically, can mimic other, acute surgical conditions. However, because this
process is generally considered self-limited, a familiarity with the entity
and its typical findings on CT is helpful in preventing unnecessary surgical
intervention. Segmental omental infarction may often be distinguished from
other causes of acute abdominal pain on the basis of CT findings.
References
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Clinical History
Radiologic Description
