Low serum bilirubin in chronic renal failure. Relation to haem metabolism

In renal failure serum bilirubin values are lower than normal. When renal failure is moderate this decrease is not due to a reduced-red-cell mass or to low levels of serum albumin. In splenic fine-needle aspirates from patients with renal failure, conditions for haem degradation were normal as indicated by normal activities of haem oxygenase and biliverdin reductase. Nor were the in vitro activities of these enzymes significantly depressed in the presence of ultrafiltrates of uraemic sera or of high concentrations of creatinine, urea or methylguanidine. The capacity of plasma from patients with renal failure to bind bilirubin was less than that of normal plasma, which at least partially explains the observed low values of serum bilirubin. There remains the possibility that in renal failure some bilirubin is removed from the plasma by a hitherto unknown route.