Urinalysis
Jaundice will be apparent when the serum bilirubin is three times above normal. The normal value of bilirubin is <17 micromol/L.
A urinalysis will be useful in the initial stages of differentiating the causes of jaundice. It will also guide further investigations.
Pre-hepatic hyperbilirubinaemia
Unconjugated bilirubin is bound to albumin and is not water soluble. Therefore, it cannot appear in the urine.
Post-hepatic hyperbilirubinaemia
Conjugated bilirubin is water soluble and therefore appears in the urine. Urobilinogen is absent due the inability of conjugated bilirubin to be excreted in to the small intestine.
| Pre-hepatic hyperbilirubinaemia | No bilirubin | Urobilinogen ++ |
| Hepatic hyperbilirubinaemia | Bilirubin + | Urobilinogen ++ |
| Post-hepatic hyperbilirubinaemia | Bilirubin ++ | No Urobilinogen |
Urinalysis findings
The findings in the urine should then be confirmed by measuring direct (conjugated) and total bilirubin levels:
Urine is negative for bilirubin
Urine is positive for bilirubin
