Used in : the diagnosis as well as monitoring of carcinoid syndrome of the intestine Intestinal carcinoids can produce excess serotonin. Serotonin gets metabolized to 5-HIAA. This is quite specific for the diagnosis of carcinoid tumours . Interpretation: Elevated excretion of 5-HIAA is a possible indicator of a carcinoid tumour i.e a carcinoid which is producing serotonin. One must take care to ensure no dietary factors can be confounding the result in this case. Eg: Avoid intake of foods with a high content of serotonin (avocados,dates,eggplants, most fruits,nuts and tomato related products.) This can alter the test result for upto 2 days after consumption. Avoid coffee and related beverages for upto 2 days before the test. Carcinoid tumors present with flushing, heart ailments and enlargement of the liver.