1. Strangulated Hernias.

—By far the most common of all the causes of acute obstruction are strangulated hernias. These are, however, treated by themselves in a distinct chapter.

2. Intussusception or Invagination.

—These terms imply a protrusion or prolapse of one part of the intestine into the lumen of an immediately adjoining portion. This is found to be the cause of perhaps one-third of the total number of cases. Enteric invaginations occur along any portion of the small intestine, being more common in the lower portion and rare in the uppermost. They seldom attain great length and are often very short. The ileocecal is the most common variety, since obviously it is the easiest of occurrence, the ileum protruding into the cecum or the ileum and cecum together passing into the ascending colon. Colic invagination may occur anywhere along the large bowel, being again more common near its distal termination. The colon may descend into the colon or the sigmoid into the rectum, even to such an extent as to present at the anus or possibly protrude. Statistics show that the ileocecal occurs in 44 per cent., the enteric in 30 per cent., the colic in 18 per cent., and the ileocolic in 8 per cent. of cases.

While the surgeon is concerned only with the obstructive form of intussusception it is of interest to know that the condition occurs occasionally shortly before death and is then spoken of as the intussusception of the dying, being usually due in these cases to irregularity and uncertainty of peristalsis during the concluding hours of life; paralysis occurring at one portion of the intestinal tube and abnormal activity just above it. These conditions are discovered at autopsy, and can be recognized as such by the absence of exudate or of any attempt either at repair or inflammation. They occur most commonly in the young and may also be multiple. In direction intussusception is practically always descending, although there may be a secondary and associated ascending movement, the latter being unimportant.

Double intussusceptions are somewhat common, and triple or multiple have been described.

Cross-section of an invaginated bowel will show that on each side one must pass through three distinct layers of bowel wall. That portion which is intruded is spoken of as the intussusceptum, while that portion which receives the latter is known as the intussuscipiens ([Fig. 560]). Obviously when invagination occurs the mesentery should be drawn in with the intussusceptum, while traction upon it should increase with advance of the included bowel. This is particularly often seen in ileocolic varieties where the ileum, with its mesentery, may travel the whole length of the colon and even present at the anus. Moreover, this may occur within a relatively astonishing short time, and the fact that the intussusceptum may be felt in the rectum within a few hours after the occurrence of the first symptoms is a fact not easily to be explained.

Fig. 560