Rectal 13N-ammonia test (13N-liver/heart ratio), hepatic sinusoidal pressure and prevailing portal flow direction in cirrhosis of the liver.

The 20 minutes' liver/heart activity ratio after rectal administration of 13N-ammonia was abnormally low (less than 2.25) in 12 of 26 patients with cirrhosis of the liver. An abnormal conventional rectal arterial ammonia test (porta-systemic shunts), an abnormally low urea index (prevailing hepatofugal portal venous flow direction), marked portal hypertension (hepatic sinusoidal pressure greater than or equal to 8 mm Hg), ascites and extreme enlargement of the spleen occurred significantly more often in the patients with an abnormally low 13N-liver/heart ratio than in those with a ratio greater than or equal to 2.25. There was no correlation between the 13N-liver/heart ratio and absence or presence of oesophageal varices. The non-invasive rectal 13N-ammonia test appears to be an easy to perform, informative test in cirrhosis of the liver.