Pathophysiology in the acute afferent loop syndrome. A study in rats.

The afferent loop syndrome, i.e. occlusion of an afferent intestinal loop after a Billroth II partial gastrectomy, was induced in rats. After various time intervals the animals were killed and the haematocrit and serum osmolality were determined. The content of the occluded loop was analysed with respect to volume, bacterial flora and osmolality. In some cases a sample of the content was incubated at 37 degrees C and the osmolality determined at regular intervals. Groups of animals were studied in this way after 30 min or 1, 4, 8 or 12 h of occlusion. The haematocrit rose with time after the occlusion. The osmolality of the plasma and of the content of the occluded loop did not increase. The volume of fluid in the occluded loop increased continuously with time--from an average of 0.5 ml in the control cases to 6.1 ml after 12 h of occlusion. Experiments in vitro showed that the initial osmolality of the content of the loop was 300 mOsm. After incubation of the samples this increased by 43 to 146 percent. The bacterial content of the loop, including Clostridium perfringens, increased significantly. The results indicate that a marked breakdown of substances takes place in such an occluded intestinal loop, which increases the osmolality. As a result fluid is immediately attracted to the loop to keep the osmolality constant. A combination of this fluid increase due to osmosis and contractions of the intestinal wall leads to a pressure in the occluded loop which considerably exceeds the pressure in the common bile duct due to secretions from the pancreas and liver.