L18: Clinical Approach To Icterus (Gallagher) Flashcards
Pigments that freely filter through the kidney
C. Bilirubin
Urobilinogen
Urobilin
Stercobilinogen
See bilirubin metabolism diagram
:)
What makes feces brown?
Stercobilin pigment (from urobilinogen)
Which forms of bilirubin are NOT freely filtered in the kidney?
Anything albumin-bound, so unconjugated bilirubin and delta bilirubin.
Conjugated bilirubin IS freely filtered
Bilirubinuria may precede hyperbilirubinemia, esp. In cats**
Any bilirubin in cat urine is significant
In dogs, NOT uncommon to see bilirubin in the urine (lower threshold)
May or may not be significant
When does icterus occur in serum?
Bilirubin >1.5 mg/dL
When does icterus occur in tissues?
> 2.0 mg/dL
Lipemia, hemolysis can falsely increase bilirubin
:)
3 main causes of icterus
1) Pre-hepatic (upstream increase in bilirubin that normal liver can’ adequately deal with)
2) Hepatic (hepatocytes can’t process adequately)
3) Post-hepatic (obstruction to flow)
1 cause of post-hepatic icterus in dog
Pancreatitis
Differentials for pre-hepatic icterus
Hemolysis (do PCV to rule out FIRST)**
Differentials for hepatic icterus
Hepatitis Hepatic lipidosis Neoplasia Cirrhosis Toxins/Drugs Hyperbilirubinemia of sepsis (more common in cats)
Differentials for post-hepatic icterus
- pancreatitis
- cholangitis
- cholecystitis
- choleliths
- biliary neoplasia
- GB mucocele
- Duodenal dz
- biliary duct obstruction
rule out next after ruling out pre-hepatic hemolysis
Cats like to get biliary dz, dogs like to get hepatic parenchymal dz
:)
Unusual for PSS alone to cause icterus - should look for other cause
:)
Clinical approach to icterus
- Hx
- PE
- CBC/Chem/UA
- Abd. Imaging
- fecal evaluation
- liver function testing
- PLI
- coag testing
- infectious dz testing
- hepatic tissue sampling
Important things to ask in hx of liver patient
- vaccination status
- drugs/toxins
- travel history
- acute vs. chronic dz
Important things to assess on PE of liver patient
- icterus
- hepatomegaly
- ascites
- abd. Pain
- MM color
Things to evaluate on CBC for liver patient
- PCV/HCT
- evidence of hemolysis: hemolyzed serum, schistocyes, spherocytes, etc.
Things to evaluate on Chemistry in liver patient
- bilirubin
- liver enzymes
- BUN, albumin, cholesterol, glucose
Things to look for on UA in liver patient
- bilirubinuria (bilirubin crystals)
- ammonium urate crystals
Abd. Imaging in the liver patient
- Rads: liver size, extrahepatic lesions
- US: evaluate liver parenchyma, biliary tree, extrahepatic lesions (GB mucocele, GIT changes, etc.)
Fecal evaluation of liver patient
Melena may indicate chronic hepatitis or other dz that effects both the liver and GIT
Acholic feces indicate bile duct obstruction
Perform fecal sedimentation to look for liver flukes in cats, or tx presumptively with praziquantel
Liver function testing in icteric patient
- Bile acids rarely indicated, esp. If patient clinically icteric
- Resting ammonia
PLI test for pancreatitis
- can have false neg. and false positive
- should also use US to look for pancreatitis (will see hypoechoic pancreas, abd. Effusion)
When should you do coag testing on icteric patient?
-if liver dysfunctional or there has been a chronic biliary duct obstruction
Chronic bile duct obstruction –> malabsorption of fat-soluble vitamins
This is why you should supplement vitamin K in cats prior to biopsy if PT/PTT prolonged
Lepto affects the liver and what other major organ
Kidneys
Hepatic tissue sampling types
- cytology
- histopath
- culture
- bile evaluation (easier to isolate bacteria from bile than liver parenchyma)
Very high bilirubin is common in hemolysis patients: why?**
Cytokines inhibit the uptake of bilirubin in the liver
Will bilirubin be elevated in dog with diabetes?
No, but ALP can be
Cats commonly get neutrophilic or lymphocytic cholangitis
:)
3 forms of bilirubin
1) Unconjugated: albumin bound, water insoluble
2) Conjugated: glucuronic acid, water soluble
3) Delta: covalently bound to albumin, long-lasting
