Main directions of differential search
Differential diagnosis of jaundice is based on comparing laboratory and clinical data. There are three key variants of bile pigment metabolism pathology:
- Hemolytic (prehepatic): caused by massive erythrocyte destruction and excessive production of free pigment.
- Parenchymatous (hepatic): associated with hepatocyte damage and impaired uptake, conjugation, and excretion of bilirubin.
- Obstructive (posthepatic): occurs due to impaired bile passage into the intestine resulting from biliary tract obstruction.
Laboratory markers of jaundice
To accurately determine the type of pathology, biochemical parameters of blood, urine, and stool are analyzed:
| Parameter | Hemolytic | Parenchymal | Obstructive |
|---|---|---|---|
| Blood bilirubin | ↑ indirect | Mixed (direct and indirect) | ↑↑ direct (sharp) |
| ALT, AST | Normal | Sharply ↑ (cytolysis) | Normal or moderately ↑ |
| ALP, GGT | Normal | Moderately ↑ | Sharply ↑ (cholestasis) |
| Urine bilirubin | Absent | Present | Present |
| Urobilin in urine | ↑↑ | Decreased / present | Absent |
| Stool | Hypercholic | Hypocholic | Acholic |
Clinical and laboratory characteristics of variants
Each type of jaundice has its own pattern of disorders:
- Hemolytic jaundice is characterized by a sharp increase in indirect bilirubin with normal cholestasis enzymes. A complete blood count reveals decreased hemoglobin and red blood cells, anisocytosis and poikilocytosis, while urine shows excess urobilin.
- Parenchymatous jaundice combines signs of cytolysis (high ALT and AST) and cholestasis. Both direct and indirect bilirubin increase in the blood, direct bilirubin appears in the urine while urobilin decreases, and the stool becomes light-colored.
- Obstructive jaundice is characterized by pronounced cholestasis: direct bilirubin and the activity of alkaline phosphatase and GGT sharply increase. Urine darkens due to bile pigments, and stool becomes completely discolored (acholic).
Additional workup plan
When jaundice syndrome is detected, the diagnostic workup includes:
- Comprehensive metabolic panel with evaluation of bilirubin fractions, transaminases, alkaline phosphatase, total protein, and its fractions.
- Repeat complete blood count with reticulocyte count and erythrocyte morphology assessment.
- Urinalysis for urobilin and bile pigments.
- Serological tests and PCR to rule out viral hepatitis.
- Instrumental imaging methods (ultrasound, CT, MRI) if biliary obstruction is suspected.
Hemolysis — indirect (lots of blood destroyed), Liver — mixed (everything broken down a bit), Obstruction — direct (plug in the pipe, bile flows back into the blood). ALT/AST spike in hepatitis, while ALP/GGT spike in posthepatic obstruction.
Class and exam questions
Why does indirect bilirubin not pass into the urine in hemolytic jaundice?
Indirect (unconjugated) bilirubin is tightly bound to plasma albumin, so it does not pass through the renal filter and is absent in urine.
Which enzyme marker indicates hepatocyte damage, and which indicates cholestasis?
ALT and AST serve as markers of cytolysis and hepatocyte damage. Alkaline phosphatase (ALP) and GGT are markers of cholestasis and biliary tract damage.
Why does stool become acholic in obstructive jaundice?
Stool discoloration (acholia) occurs due to complete biliary tract obstruction, causing bile pigments and stercobilin to stop entering the intestine.
What else to study on this topic
- Pathogenesis of cytolysis and cholestasis syndrome in viral hepatitis
- Hereditary enzymopathies of bilirubin metabolism
- The role of reticulocytosis and anisocytosis in the diagnosis of hemolytic anemias
- Instrumental imaging methods in obstructive jaundice (ERCP, ultrasound, CT)
- Toxic and drug-induced hepatopathies as a cause of jaundice syndrome
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