Page 755 - Clinical Small Animal Internal Medicine

67 Diseases of the Gallbladder and Extrahepatic Biliary Ducts 723

Vomiting may be a clinical sign associated with biliary Blood biochemistry in biliary tract disease varies
VetBooks.ir disease itself or caused by an underlying associated prob­ depending upon the degree of biliary obstruction as well
as the accompanying hepatic and pancreatic disease.
lem such as pancreatitis. A history of dietary indiscretion
In an icteric patient, total bilirubin will be increased. If
or ingestion of fatty foods may be relevant in cases of acute
pancreatitis. Abdominal pain may result from the obstruc­ the patient has significant cholestasis, then bile acids will
tion or distension of the bile ducts or gallbladder or from also be increased. If total bilirubin is increased then
inflammation of the biliary tract and surrounding area nothing additional may be inferred from measurement
(e.g., local peritonitis). Patients with biliary mucocele may of bile acids or performing a bile acid stimulation
also exhibit abdominal pain and, if significantly obstruc­ test – the patient has either significant hepatic functional
tive, may become jaundiced. Jaundice (icterus) becomes compromise or bile duct obstruction.
clinically evident as yellow discoloration of the mucus Increases of the concentration of biliary canalicular
membranes, skin, and sclera when the serum bilirubin enzymes in the blood are expected (alkaline phosphatase
exceeds around 2 mg/dL. The exact concentration at [ALP], gamma‐glutamyl transferase [GGT]) with choles­
which icterus becomes clinically visible will depend upon tasis or biliary tract inflammation. Bile acids are toxic to
the patient’s own pigmentation and hemoglobin concen­ hepatocytes, so it is extremely common for animals with
tration (mucous membrane pallor makes icterus more bile stasis to have elevation in hepatocellular enzymes
evident). Total biliary obstruction prevents pigmentation (alanine aminotransferase [ALT], aspartate aminotrans­
of the feces, resulting in pale “acholic” feces. ferase [AST]). Patients with concurrent hepatic paren­
chymal disease may also have increased hepatocellular
enzymes. If hepatic disease is advanced enough to impair
Diagnosis hepatic function, then urea and albumin may be reduced
due to poor hepatic synthesis and conversion. Similarly,
Clinical Examination coagulation factors may be depleted due to reduced
recycling of the vitamin K‐dependent factors (II, VII, IX,
It should be apparent from clinical examination if the X), resulting in prolonged coagulation times (prothrom­
patient is jaundiced, but jaundice is only clinically evident bin time, activated partial thromboplastin time).
when serum bilirubin levels exceed 2 mg/dL. As previ­ The inflammatory response may cause increased
ously mentioned, how evident hyperbilirubinemia is will synthesis of globulins. Pancreatitis may be reflected by
depend upon multiple factors. Examination of the sclera elevations of amylase and lipase, due to leakage from the
or internal aspect of the pinna (the latter particularly in pancreas, but these enzymes have poor specificity and may
cats) may display more obvious evidence of icterus. be spuriously elevated in hemoconcentrated patients and
Cranial abdominal pain may manifest as a hunched patients with other diseases. Amylase and lipase are even
posture, “prayer posture” or via the patient’s response to less sensitive and specific in cats than in dogs. Pancreatic
palpation. Once again, how evident this subjective find­ species‐specific lipase is a more sensitive and specific test,
ing is will depend upon patient factors and also concur­ but it must be remembered that a positive result does not
rent problems such as pancreatitis. Pancreatic pain necessarily indicate that pancreatitis is the primary prob­
usually localizes to the right cranial abdominal quadrant, lem as gastrointestinal disease, peritonitis, or pancreatic
but may be more diffuse. In some patients, pancreatic neoplasia can also result in increased pancreatic specific
pain does not manifest until pressure is placed directly lipase. Additonally, a normal value does not exclude pan­
upon the pancreas during ultrasonography. A very dis­ creatitis as a possible differential diagnosis.
tended gallbladder might be palpable beyond the hepatic
margin in some patients, but this is unusual. If rupture of
the biliary tract has occurred then an abdominal effusion Hematology
may be present, potentially resulting in a fluid wave on The complete blood count can reflect the inflammatory
ballottement. Often, however, patients with bile perito­ disease by revealing increased numbers of neutrophils
nitis have tensed abdominal muscles, because of the which, in marked inflammation or infection, may exhibit
associated pain, which limits clinical examination. a left shift or toxic changes.

Blood Chemistry Urinalysis
Following centrifugation, the plasma or serum of a jaun­ Icteric patients are, by definition, hyperbilirubinemic,
diced patient’s blood will appear deep yellow (icteric). which results in bilirubinuria, imparting a deep yellow
This interferes with some colorimetric blood biochemis­ color to the urine. On microscopic examination of urine
try tests. sediment, bilirubin crystals may be evident.