Diagnostic ultrasound ( PDFDrive )

288 PART II Abdominal and Pelvic Sonography
A
B
FIG. 8.35 Right-Sided Diverticulitis in Two Patients. Transverse sonograms through the ascending colon (AC) show a hypoechoic pouchlike
projection, representing the inlamed diverticulum, which arises from (A) the lateral wall of the gut and (B) the medial border of the gut. Both are
surrounded by inlamed fat (arrows).
patients with typhlitis and colitis, although other organisms have
been implicated. Sonographic study most oten shows striking
concentric, uniform thickening of the colon wall, usually localized
to the cecum and the adjacent ascending colon 64 (Fig. 8.36). he
colon wall may be several times the normal thickness, relecting
inlammatory iniltration throughout the gut wall. 65,66 Acute
abdominal catastrophe in patients with AIDS is usually a complication
of CMV colitis with deep ulceration and may result in
hemorrhage, perforation, and peritonitis. 67 Tuberculous colitis
may similarly afect the right colon and is frequently associated
with lymphadenopathy (particularly involving the mesenteric
and omental nodes), splenomegaly, intrasplenic masses, ascites,
and peritoneal masses, all of which may be assessed using
sonography.
Mesenteric Adenitis With Terminal Ileitis
Mesenteric adenitis, in association with acute terminal ileitis, is
the most frequent GI cause of misdiagnosis of acute appendicitis.
Patients typically have RLQ pain and tenderness. On the sonographic
examination, enlarged mesenteric lymph nodes and mural
thickening of the terminal ileum are noted. Yersinia enterocolitica
and Campylobacter jejuni are the most common causative
agents. 68,69
Right-Sided Segmental Omental Infarction
Right-sided segmental infarction of the omentum is a rare
condition invariably mistaken clinically for acute appendicitis. 70
Of unknown origin, it is postulated to occur with an anomalous
and fragile blood supply to the right lower omentum, making
it susceptible to painful infarction. Patients experience RLQ pain
and tenderness and are diagnosed clinically with acute appendicitis.
On sonography, a plaque or cakelike area of increased
echogenicity, suggesting inlamed or iniltrated fat, is seen
supericially in the right lank with adherence to the peritoneum 70
(Fig. 8.37). No underlying gut abnormality is shown. Because
segmental infarction is a self-limited process, its correct diagnosis
will prevent unnecessary surgery. CT scan is conirmatory,
showing streaky fat in a masslike coniguration in the right side
of the omentum.
Left Lower Quadrant Pain
he sonographic evaluation of the patient with let lower quadrant
(LLQ) pain is less problematic than that of the patient with pain
on the right side as acute diverticulitis is the explanation for the
overwhelming majority of cases for which a valid explanation
for the pain is found. he diagnostic features of acute diverticulitis
are also less variable than those for acute appendicitis, making
a suspicion of diverticulitis a good indication for the use of
sonographic examination.
Acute Diverticulitis
Diverticula of the colon are usually acquired deformities and
are found most frequently in Western urban populations. 71 he
incidence of diverticula increases with age, 72 afecting approximately
half the population by the ninth decade. Muscular dysfunction
and hypertrophy are constant associated features. Diverticula
are usually multiple, and their most common location is the
sigmoid and let colon. Both acute diverticulitis and spastic
diverticulosis may be associated with a classic triad of presentation:
LLQ pain, fever, and leukocytosis. Diverticula may also be