Carbohydrate antigen 19-9 as a diagnostic marker for hepatic cyst infection in autosomal dominant polycystic kidney disease.

The diagnosis of hepatic cyst infection is difficult in patients with autosomal dominant polycystic kidney disease (ADPKD). We hypothesized that carbohydrate antigen 19-9 (CA 19-9), secreted by the biliary epithelium lining the cysts, is overproduced in the case of cyst infection. In this report, we describe 3 patients with ADPKD with hepatic cyst infection, all with functioning kidney transplants, who had markedly increased serum CA 19-9 levels. Furthermore, CA 19-9 level was extremely increased in cystic fluid obtained in 2 of these individuals. Corresponding with clinical improvement, there was a marked decrease in serum CA 19-9 level in all 3 patients. To assess the potential applicability of these findings, serum CA 19-9 was measured in asymptomatic patients with ADPKD with known liver cysts and in controls without ADPKD. Although serum CA 19-9 levels were significantly higher in asymptomatic patients with ADPKD than in controls, they were markedly increased in patients with cyst infection compared with either asymptomatic ADPKD patients or controls. Immunostaining for CA 19-9 showed strong positivity in biliary tree epithelia and cysts of polycystic livers from patients with ADPKD that appeared more intense than in normal livers. Although further study is necessary, these data suggest that serum CA 19-9 level is markedly increased during liver cyst infection in kidney transplant recipients with ADPKD and has potential utility as a diagnostic marker.