Page 630 - Small Animal Internal Medicine, 6th Edition

602 PART IV Hepatobiliary and Exocrine Pancreatic Disorders

able to palpate it in a dog with EBDO unless the gallbladder cases with complete, persistent EBDO should be operated on
is greatly enlarged. as quickly as possible because of the fear that refluxed bile
VetBooks.ir Diagnosis acids will inevitably lead to cirrhosis unless the obstruction
is relieved rapidly. However, more recent evidence suggests
Affected dogs often show hyperbilirubinemia, high serum
erwise clinically well dogs for days to weeks while transient
ALP, GGT, fasting and postprandial serum bile acid (SBA), that medical management can be safely undertaken in oth-
and cholesterol concentrations, and less severe changes in biliary tract obstruction resolves, and clinicians should not
serum ALT activity. SBA concentrations increase early in be too quick to go in surgically in a dog with EBDO second-
dogs with biliary stasis; in these circumstances, the degree of ary to pancreatitis. There is no evidence in the veterinary lit-
SBA level elevation gives no indication of liver function. erature to guide clinicians on how often cirrhosis ensues and
Generally, more severe cholestatic lesions are associated with how long a complete biliary obstruction should be allowed to
more severe clinicopathologic changes. Radiographically, continue before surgical intervention. However, in a review
there may be evidence of hepatomegaly and a mass effect in of biliary tract obstruction caused by chronic pancreatitis
the area of the gallbladder on survey abdominal films. Gas (CP) in humans, Abdallah et al. (2007) pointed out that as
shadows associated with the gallbladder and other biliary few as 7% of cases developed subsequent biliary cirrhosis.
tract structures could be ascribed to ascending infection Biliary obstruction caused by CP in humans is considered to
with gas-forming organisms. The cause of cholelithiasis in be transient if it resolves within 1 month; most cases are tran-
dogs is unclear, and they may also be found in asymptomatic sient because the biliary obstruction resolves as the edema of
dogs. These concretions are radiolucent unless they contain the acute-on-chronic inflammation resolves. In the absence
calcium, which occurs about 50% of the time. Inflammatory of marked pain or a mass, the patient will be monitored for 1
abdominal effusion is expected in dogs with bile peritonitis month and only treated surgically if the jaundice is persistent
but not in those with most causes of EBDO, except for effu- after this or there is suspicion of neoplasia.
sions associated with pancreatitis or pancreatic cancer. As with any other form of liver disease, it is important
Ultrasonography helps differentiate medical from surgi- to stabilize the patient with fluids and electrolytes, and
cal causes of EHBO, although this imaging modality is cer- to perform a hemostasis profile and platelet count before
tainly not foolproof. Dilated and tortuous hepatic bile ducts surgery. Prolonged coagulation times may respond to vitamin
and CBD, as well as gallbladder distention, are convincing K 1 injections 0.5–1 mg/kg SC × 3 doses at 12-hour intervals
ultrasonographic evidence of EBDO at the CBD or sphincter prior to surgery (to be consistent with earlier recommenda-
of Oddi. When dilated biliary structures are seen, it might tions), but if not, a fresh-frozen plasma transfusion is advis-
be difficult to distinguish EBDO that requires surgical inter- able before surgery to replace clotting factors. If the site of
vention from resolving transient EBDO associated with obstruction or biliary injury is not identified, at least tissue
severe acute-on-chronic pancreatitis or from nonobstructive (e.g., liver, gallbladder mucosa) and bile specimens can be
biliary disease (e.g., bacterial cholecystitis or cholangitis) obtained for histopathologic and cytologic evaluation, bac-
unless a source of obstruction is specifically identified (e.g., terial culture, and sensitivity testing. Any abdominal fluid
pancreatic mass, cholelith in the CBD). Prolonged fasting should be analyzed cytologically and cultured for aerobic
causes gallbladder enlargement because of delayed evacua- and anaerobic bacteria. A liver biopsy specimen should also
tion and should not be overinterpreted. In addition, cystic be obtained in all cases. Typical hepatic histopathologic find-
hyperplasia and epithelial polyp formation are common ings in dogs with early EBDO are canalicular bile plugs and
lesions in older dogs and should not be confused with cho- bile ductular proliferation, with degrees of periportal inflam-
leliths in the gallbladder. A stellate appearance to the con- mation and fibrosis in chronic cases. Confounding biliary
tents of the gallbladder is characteristic of gallbladder infection can incite a stronger inflammatory reaction in the
mucocele (see Fig. 36.8). Monitoring the serum bilirubin periportal region. However, it is impossible to diagnose a
concentration to determine when to intervene surgically is primary biliary tract infection from a liver biopsy alone.
not worthwhile because it begins to decline over days to Surgical goals are to relieve biliary obstruction or leakage
weeks, without relief of obstruction, in cats and dogs with and restore bile flow. Reconstructive procedures to divert
experimentally induced EBDO. Conversely, in some dogs a bile flow can be performed if the cause of EBDO cannot be
significant proportion of bilirubin becomes irreversibly corrected. However, because these carry a poor long-term
bound to albumin in the circulation (biliprotein), resulting prognosis, less invasive procedures such as stenting are pre-
in delayed clearance and continued elevation of the serum ferred whenever possible.
bilirubin concentration for up to 2 weeks after the initial In cases without complete biliary obstruction (e.g., some
insult has resolved. choleliths) or with transient obstruction (e.g., most cases of
acute-on-chronic pancreatitis), medical management alone
Treatment and Prognosis is indicated. The choleretic ursodiol is indicated as treatment
If the distinction between medical and surgical causes of in these cases, provided that complete EBDO has been ruled
jaundice is not clear, it might be safer to proceed surgically to out. Choleliths may also move using this drug. The recom-
avoid excessive delays in diagnosis, particularly if bile perito- mended dosage is 10 to 15 mg/kg total, PO daily, preferably
nitis is suspected. The previously established principle is that split into two doses. In addition, all cases (both medical and