Experimental regional enteritis in pigs.

Lymphatic obstruction is constantly present in regional enteritis, but its role in the pathogenesis is poorly understood. To clarify this the mesenterial lymphatics of the terminal ileum were obstructed in 21 pigs chosen for experiments because spontaneous ileitis is common in pigs. Long-lasting obstruction was produced by injecting formaline into regional lymph nodes. The growth of the pigs was retarded. Their ileum became reddish and oedematous with numerous intra-abdominal adhesions, and mucosal ulcerations. Eleven pigs developed fistulae; none had chylous ascites. Histologically the subserosa was infiltrated by round and giant cells giving an impression of granulomatous inflammation. Many lymphatics were thrombosed. The lymphoid tissue was hyperplastic. These changes became more prominent with extensive subserosal fibrosis after three weeks, when the oedema diminshed. Transmural inflammation with round cell aggregations was then the most typical feature. Purulent infection with crypt abcesses appeared near the fistulae. If the function of lymphatics is destroyed, transport of particles too big to enter blood vessels is inhibited. This produces chronic irritation and oedema with declining tissue nutrition and oxygenation, thus causing fibrosis. Moreover, the intestinal lumen is a source of infections, and the oedematous tissue is easily infected. This may lead to mucosal ulcerations and, progressively, to fistulae.