Portal circulation in patients with chronic liver diseases was evaluated by [99mTc]pertechnetate per-rectal scintigraphy. Technetium-99m pertechnetate (10 mCi) was instilled into the upper rectum, and serial scintigrams were taken. Radioactivity curves for the liver and heart were then recorded sequentially. Through analysis of these curves, the per-rectal portal shunt index (Sl) was calculated for six healthy subjects and 228 patients, 59 with chronic hepatitis, seven with idiopathic portal hypertension, six with primary biliary cirrhosis, and 156 with cirrhosis. In the healthy subjects, the Sl was 1.9-5.2% (mean 4.1%). In hepatitis, the mean Sl was 7.1%, and in cirrhosis, 52.9%. The Sl was higher in cirrhotic patients with esophageal varices than in those without (p less than 0.001), and in cirrhotic patients with encephalopathy than in those without (p less than 0.01). For some patients with portal hypertension, portal collateral circulation could be depicted, and images of changes in the portal collateral circulation after vascular anastomosis were seen.