Diagnostic ultrasound ( PDFDrive )

200 PART II Abdominal and Pelvic Sonography
Causes of Gallbladder Wall Thickening
GENERALIZED EDEMATOUS STATES
Congestive heart failure
Renal failure
End-stage cirrhosis
Hypoalbuminemia
INFLAMMATORY CONDITIONS
Primary
Acute cholecystitis
Cholangitis
Chronic cholecystitis
Secondary
Acute hepatitis
Perforated duodenal ulcer
Pancreatitis
Diverticulitis/colitis
NEOPLASTIC CONDITIONS
Gallbladder adenocarcinoma
Metastases
MISCELLANEOUS
Adenomyomatosis
Mural varicosities
or diverticulitis, and even pyelonephritis can demonstrate a
Murphy sign and sympathetic gallbladder wall thickening (Fig.
6.42). Absence of a distended gallbladder and gallstones is oten
a clue to the nonbiliary origin of the cholecystic process.
Gangrenous Cholecystitis
When acute cholecystitis is especially severe or prolonged, the
gallbladder may undergo necrosis. Sonographic indings of
gangrenous cholecystitis include nonlayering bands of echogenic
tissue within the lumen representing sloughed membranes and
blood (see Fig. 6.40D). he gallbladder wall also becomes irregular,
with small collections within the wall that may represent abscesses
or hemorrhage. 76 Murphy sign is absent in two-thirds of patients, 86
presumably because of necrosis of the nerve supply to the gallbladder.
Hemorrhagic cholecystitis represents a rare gangrenous
process marked by bleeding within the gallbladder wall and
lumen. he clinical symptoms are indistinguishable from gangrenous
cholecystitis, and only occasionally does the patient
experience a gastrointestinal bleed.
Perforated Gallbladder
Perforation of the gallbladder occurs in 5% to 10% of patients
with acute cholecystitis, generally in cases of prolonged inlammation.
76 he focus of perforation, seen as a small defect or rent
in the wall of the gallbladder, is oten visible (see Fig. 6.40, Video
6.11). Clues to perforation are the delation of the gallbladder,
with loss of its normal gourdlike shape, and a focal pericholecystic
luid collection. he latter is oten a small luid collection around
the wall defect, unlike the thin rim of luid around the entire
organ in uncomplicated cholecystitis. 87 he collection may have
internal strands typical of abscesses elsewhere (see Fig. 6.40E).
Perforation of the gallbladder may extend into the adjacent liver
parenchyma, forming an abscess collection. he presence of a
cystic liver lesion around the gallbladder fossa should suggest a
pericholecystic abscess.
Emphysematous Cholecystitis
Emphysematous cholecystitis represents less than 1% of all
cases of acute cholecystitis, but it is rapidly progressive and
fatal in approximately 15% of patients. Emphysematous
cholecystitis difers from acute cholecystitis in several ways. It is
three to seven times more common in men than women; about
one-half of patients have diabetes; and one-third to one-half
have no gallstones. 76,88 he gas is produced by gas-forming
bacteria, presumably ater an ischemic event afecting the
gallbladder. 88 hese patients have a much higher incidence of
gallbladder perforation than those with typical acute cholecystitis,
and urgent surgical treatment is advocated for all
patients.
he appearance of emphysematous cholecystitis on sonography
depends on the amount of gas present (see Fig. 6.40G-I). he
gas is oten within both the lumen and the wall of the gallbladder.
Small amounts of gas appear as echogenic lines, with posterior
dirty shadowing, reverberation, or ring-down artifact. Large
amounts of gas can be more diicult to appreciate. he absence
of a normal gallbladder is a clue. A bright, echogenic line with
posterior dirty shadowing is seen within the entire gallbladder
fossa. Movement of gas bubbles is a helpful inding and may be
precipitated by compression of the gallbladder fossa. Pneumobilia
may also be seen. 88
Acalculous Cholecystitis
Acalculous cholecystitis may occur in patients with no
risk factors but is more common in critically ill patients,
who thus have a worse prognosis. Risk factors include
major surgery, severe trauma, sepsis, total parenteral nutrition,
diabetes, atherosclerotic disease, and HIV infection. 80
In nonhospitalized patients, it is more common in older male
patients with atherosclerotic disease, 89 who have a much better
prognosis.
he diagnosis of acalculous cholecystitis can be diicult
because gallbladder distention, wall thickening, internal sludge,
and pericholecystic luid may all be present in critically ill
patients without cholecystitis. 90 Patients may be obtunded or
receiving analgesics, reducing the sensitivity of Murphy sign.
he combination of indings suggests the diagnosis; the more
signs present, the greater is the likelihood of cholecystitis. 91
Nevertheless, cholescintigraphy or percutaneous sampling of
the luminal contents should be used more liberally to assist
in the diagnosis.