This constitutes the most common form of internal fistula. Brinton noted its existence in eleven out of the 507 cases of gastric cancer which he collected (2.17 per cent.), while Dittrich estimated its frequency at 3.75 per cent, and Lange at 3.8 per cent. Out of 1,142 cases of gastric cancer, including 265 of our own, we find that a fistulous communication existed between the stomach and the colon in thirty, or in 2.5 per cent. In almost every instance the primary growth was situated at the lower border of the stomach, near the pylorus, but Lyon has recorded a case in which it occupied the lesser curvature, and in one of our own series the anterior wall of the fundus was affected. With regard to its mode of formation, it would appear that the fistula may arise in three ways. In the majority of cases the neoplasm attacks the bowel by direct extension, the two viscera having become previously united by adhesions. Less frequently a large growth forms between the stomach and the bowel, and subsequently infiltrates and destroys the contiguous portions of the two organs. In such the opening is usually found on the posterior aspect of the stomach and at the upper margin or on the anterior surface of the colon, while an irregular sloughing cavity intervenes between the two. Lastly, the gastric disease may set up a localised abscess, either within the lesser sac of the peritoneum or between the great curvature and the transverse colon, which subsequently bursts into the bowel. In this latter variety secondary openings may occur in other directions, and fistulous communications be established not only with the colon, but also with the duodenum, jejunum, or the umbilicus.
An abnormal communication between the stomach and the small intestine is much less frequent than the preceding. Brinton observed it only once among his 507 cases, but three examples occur in our own series. It is chiefly met with in cases where the stomach has been partially dislocated and the pylorus has contracted adhesions with the small bowel. The perforation of the gut is almost always the result of direct invasion of its walls, and the jejunum is usually affected. When the fistula results from the rupture of a perigastric abscess a secondary communication with the colon is apt to occur. In those exceptional cases where the diseased pylorus occupies the cavity of the pelvis a fistula may be established with the ileum, caecum, sigmoid flexure, or the rectum.
This variety is very rare, and is usually caused by perforation of the posterior wall of the stomach close to the pylorus, whereby a sloughing cavity is formed behind the organ, which finally opens into the second portion of the duodenum. In some cases the pancreas is destroyed in the process, or a fistulous track is established through its substance (Foville). A secondary communication with the colon is not infrequent (Mailliot). Occasionally the pyloric growth directly invades the wall of the bowel, and should the disease also involve the colon, the contents of the duodenum will pass into the large intestine through the intermediate stomach (Osier).
This occasionally results from an ulcerating growth of the cardiac end of the stomach which has contracted adhesions with the upper part of the pylorus. Kinking and obstruction of the first part of the duodenum usually accompany this condition, and occasionally the involvement of the bowel by the disease leads to the establishment of a gastro-duodenal fistula.