Selective mesenteric vein catheterization and plasma serotonin determination in patients with carcinoid tumors

Selective abdominal vein catheterization with blood sampling for serotonin determination was evaluated regarding its use in the diagnosis, location, and characterization of carcinoids. Serotonin was determined in a platelet‐poor plasma fraction (PPP) by an enzymatic procedure . In 5 normal subjects the concentration of serotonin in PPP in the celiac artery, the hepatic vein, and different intestinal and pancreatic veins ranged from 1.2 to 5.4 ng/ ml. In 10 patients with carcinoid tumors, the concentration of serotonin in tumor‐draining veins was clearly elevated and ranged from 10 ng/ml to 88 ng/ml PPP. 5‐HIAA urine levels were false‐negative in 4 cases, liver scintiscan was false‐negative in 3 cases, and the angiograms were not conclusive in 2 cases . The technique with plasma serotonin determination in combination with selective catheterization is a useful complement to other investigative techniques in the diagnosis, location, and follow‐up of patients with carcinoid tumors .