Rectal administration of 13N-ammonia in cirrhosis of the liver.

13N-ammonia, applied rectally, after absorption and transportation visualises the liver. After release of 13N-aminoacids and 13N-urea by the liver, 13N-activity can be measured over other organs. In patients with porta-systemic shunts, 13N-ammonia will appear in the systemic circulation as well. In 16 controls and 26 patients with cirrhosis, activities were measured for 20 minutes over liver, spleen, heart, lungs and forearm. In all subjects, the liver was visualised within a minute, in some patients with cirrhosis faintly, however. Release by the liver of 13N-ammonia metabolites started within a few minutes. Liver/heart activity ratios proved to be more discriminating between the control- and the cirrhosis group than liver/lung and liver/spleen ratios. In the control group, the 20 minutes' liver/heart ratio was most suitable for determining the normal range. The lower normal level was found to be 2.25. Fourteen of the 26 patients with cirrhosis had a normal, 12 an abnormally low 20 minutes' liver/heart ratio.