This condition has been incidentally mentioned as occasioned by several of the lesions already described. It may be well here to sum up the various forms of intestinal obstruction and to describe the effects produced when the calibre of the intestine is interrupted.

Causes Of Obstruction

Next to hernia, the most frequent cause of obstruction is the contraction of cicatrices resulting from ulceration, and in the great majority of cases the ulcers are malignant, that is to say, they arise by the breaking down of cancers. It is to be remembered that in contractions of the calibre such as these the direct cause of the final obstruction may be the folding of the mucous membrane above the stricture, this acting like a valve to the narrowed part. Tumours also obstruct sometimes by their bulk. Similarly gall-stones, masses of faeces, collections of round worms, may occlude the calibre. Invagination is the commonest cause in children. There is also twisting or torsion. Lastly, we have obstruction by incarceration, the intestine passing into a position where a loop is caught at the neck and strangled. Hernias form the commonest examples of this kind, but there are a number of cases in which the intestine slips under a bridge or ligament, and gets, as it were, pinioned and compressed. These latter merit further consideration.

Obstruction by a bridle or ligament occurs so obviously to the mind that its frequency is apt to be overrated. In reality it forms a small proportion of the- entire cases. The abnormal band may be formed by the adhesion of normal or other structures to various parts of the abdomen so as to form bridges. Thus the vermiform appendage may adhere by its tip and form a bridge; or a Meckel's diverticulum may also similarly adhere; or the omentum may be tied down in such a way as to form a narrow bridle. But sometimes the band is itself distinctly of new-formation; there has been a local peritonitis, and two opposing surfaces have become adherent in the usual way of inflammatory adhesion, by vascular connective tissue; by the movements of the intestine the connective tissue has been dragged upon and elongated till it forms a band or ligament, which may afterwards tie down a loop of intestine. The formation of such bands is mostly the result of tubercular peritonitis which has undergone healing, recovery from this disease being more frequent than might be supposed.

A very unusual form of incarceration is that in which there is an Aperture in the mesentery through which the intestine passes. This may be produced by a tear in the mesentery. In a case observed by the author there was a large round gap about five inches in diameter with rounded edges, and obviously of long standing, perhaps congenital. The greater.part of the small intestine had become impacted in a complicated fashion into the aperture, and obstruction had finally resulted.

Results Of Obstruction

The most direct effect is that the intestinal contents accumulate in the parts of the intestine above the seat of obstruction. The bowel may be greatly distended and its muscular tissue paralyzed by the internal pressure. The stagnating faeces decompose, decomposition being more rapid and complete and absorption more considerable in the case of fluid faeces. As a result of decomposition the contents of the small intestine may acquire the characters of those of the large. This decomposition of the intestinal contents leads to several important results. In the first place there may be great formation of gas which still further distends and may produce the condition of exaggerated inflation called Meteorism. Then a return of the faeces in the reverse direction may occur, and if the decomposition is sufficiently advanced there may be a vomiting of matter having the characters of faeces. This alarming phenomenon of Stercoraceous vomiting is sometimes referred to a reverse current extending from the colon. We can hardly suppose, however, that the faeces are able to pass the ileo-caecal valve, and for the most part the vomited matters are really the stagnant contents of the small intestine which have undergone faecal decomposition. Of course there is a reverse current, else the intestinal contents would not reach the stomach. But this does not necessarily imply a vermicular movement in the reverse direction. If the intestine is distended, and is interrupted at a particular point, then the vermicular movement in the usual direc tion will carry the external layer of contents downwards to the point of obstruction. In order to accommodate this fresh arrival there must be a return current upwards in the centre of the tube. There is a similar condition to what exists normally in the stomach where the contents are carried to the pylorus, and meeting the obstructing sphincter return for the most part down the centre of the cavity towards the fundus.

Again, the products of decomposition may be absorbed to an abnormal extent and appear in the urine. There are two substances resulting from the decomposition of albuminous substances which are normally present to a limited extent in the urine, namely, Indican and Carbolic acid. In cases of obstruction these substances, one or both, are increased in quantity sometimes to a very striking extent. This increase does not occur unless the stagnation extends to the small intestine where the albuminoids are present. It does not occur therefore in ordinary constipation which affects the large intestine alone, because the albuminoids are absorbed before they reach the large intestine.

Literature

Cohnheim, Allg. Path., ii., 147, 1882; Jaffe, (Indican in urine) Virch. Arch., lxx., 72, 1877; Salkowski, ibid., lxxiii., 409,1878; Brieoer, Zeitschr. f. klin. Med., iii. '