[Secondary porphyrinuria].

The condition that the porphyrins are excreted into the urine due to impairment of bile excretion, is called as secondary porphyrinuria. The main porphyrin is coproporphyrin, there fore the condition is called as secondary coproporphyrinuria. Secondary porphyrinuria is associated with various disorders, such as hepatobiliary diseases, hereditary hyperbilirubinemia, intoxications, blood and metabolic diseases, but the etiology of secondary porphyrinuria is unclear. Coproporphyrin is divided into two isomers, one is coproporphyrin-I type and the other is coproporphyrin-III type. In normal human urine, coproporphyrin-III type is predominant, and the ratio of coproporphyrin-I to total coproporphyrin is 10-50% (% as isomer I), while in urines of hepatobiliary diseases, the ratio is 40-60%. In Dubin-Johnson syndrome, the ratio is 80-100%. Coproporphyrinuria in hepatocellular carcinoma and alcoholic liver disease may be different from that in hepatobiliary diseases, often associated with uroporphyrinuria as well as coproporphyrinuria. Coproporphyrinuria arising in blood and metabolic diseases must be taken into account of associated liver diseases.