Physical examination findings
The most common physical examination findings in patients with mucoceles are abdominal pain and icterus. A small percentage
of patients may be febrile or have abdominal distention.18
Diagnostic test results
Figure 3. A transverse ultrasonogram of a canine gallbladder containing normal biliary sludge. The echogenic material within
the gallbladder has fallen dorsally, and the supernatant of more normal bile can be appreciated ventrally as an anechoic area.
(Image courtesy of Dr. Benjamin D. Young, Texas A&M University's Large Animal Clinical Sciences Department of Radiology.)
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Laboratory evaluation and radiographic findings may vary, but common results are listed in Table 1. It may be difficult to appreciate the differences between biliary sludge and a true mucocele on ultrasonographic examination.
Biliary sludge is movable and gravity-dependent, whereas a mucocele is immobile and displays a distinctive striated or stellate
(kiwi fruit or starfish) pattern (Figures 3 & 4).17
Figure 4. A transverse ultrasonogram of a canine gallbladder containing a mucocele. This image demonstrates the classic stellate
pattern and nongravity-dependent gallbladder contents pathognomonic for mucoceles. (Image courtesy of Dr. Benjamin D. Young,
Texas A&M University's Large Animal Clinical Sciences Department of Radiology.)
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If differentiation is difficult, a second ultrasonographic examination after the administration of a cholagogue (an agent
that promotes increased bile flow from the gallbladder, such as cholecystokinin octapeptide given intravenously over one minute
at a dose of 0.04 µg/kg23 ) may be helpful. If a patient has biliary sludge, gallbladder contraction occurs within 10 minutes, and a substantial (about
40%) reduction in gallbladder volume will be evident.23
Table 1: Common Diagnostic Test Results in Dogs with Gallbladder Mucoceles
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In addition to the tests listed in Table 1, cholecystocentesis may be performed, as well as aerobic and anaerobic bacterial cultures of the bile. Anywhere from 9% to
43% of patients with mucoceles may have biliary bacterial infections, and bacterial populations are often mixed. The most
common isolates are Escherichia coli and Enterobacter, Enterococcus, and Clostridium species.24 The bacterial infections are thought to ascend from the intestines but may also be hematogenous in origin.
Histopathology
A true mucocele has hyperplastic mucus-secreting glands and may also demonstrate inflammatory infiltrates.17 In one study, gallbladder wall necrosis was diagnosed in 80% of patients with mucoceles, and hepatic pathology was often
present.17 The most common hepatic changes include cholestasis, neutrophilic inflammation, and bacterial infection.20
TREATMENT OPTIONS
Emergency surgery is necessary if the gallbladder has ruptured or a patient has septic peritonitis. Surgery is also indicated
if a dog is clinically compromised or has evidence of extrahepatic biliary duct obstruction, but the patient may need to be
stabilized with fluids, intravenous antibiotics (Table 2), antiemetics, and analgesics before anesthesia.21 Time to stabilization will vary greatly for each patient and may require one to three days. If the patient has biochemical
changes but is asymptomatic or has only mild clinical signs, medical management appears to be an appropriate choice.1
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