DISEASES OF THE RECTUM AND ANUS.
BY THOMAS G. MORTON, M.D.,
AND
HENRY M. WETHERILL, M.D., PH.G.
Diseases of the inferior and terminal portion of the large intestine may be divided into primary and secondary—the former when the morbid cause is local and independent of disease elsewhere, the latter when it is consequent upon or incident to some other bodily affection. Among the primary lesions may be classed congenital malformations, prolapse of the rectum, hemorrhoids, and some varieties of new growths; also diseases caused by local irritations, infection, or traumatism, such as proctitis, ulceration, fissure, non-malignant stricture, chancroidal invasion and primary syphilis, including obstruction of the bowel by impacted feces and foreign bodies. Thread-worms and various cutaneous eruptions about the anus may also be included among the causes of the primary diseases of this portion of the alimentary canal.
The secondary affections are quite numerous, and may be caused by direct extension of disease from the colon, as in the dysentery following typhoid fever, and follicular enteritis, or entero-colitis of children; by contiguity, from diseases in neighboring organs—e.g. ischio-rectal abscess causing fistula—or by changes in the nervous or vascular supply, such as is seen in spasmodic contraction, paralysis, epidemic dysentery, cholera, and the action of certain remedies.
The rectum, the third or terminal portion of the large intestine, has no sharply-defined upper limits: it is usually understood to begin at the sigmoid flexure, opposite the left sacro-iliac symphysis; it is from six to eight inches in length and terminates in the anus. As the sigmoid flexure is the narrowest portion of the colon, so the calibre of the first part of the rectum is narrower than the portion below, where it gradually becomes more commodious, and near the anus presents a peculiar condition of the walls which gives it a capacity for remarkable distension. The rectum, which is somewhat cone-shaped, in its anatomical and pathological characters retains those of the large intestine with slight variation. Upon the upper or first part of the rectum the duplicature of the peritoneum is continued, forming the meso-rectum, which invests the bowel, attaching it to the sacrum. Below this the middle portion of the rectum (extending to the tip of the coccyx) is attached to the sacrum by connective tissue only, but also has a peritoneal investment on the upper portion of its anterior surface.
The third or terminal part of the rectum, which is only an inch and a half in length, and is entirely without peritoneal covering, terminates at the anus. The circular and transverse muscular fibres, mucous crypts, and appendages throughout the rectum are identical with those above, except that the general muscular tunic is thicker; but the longitudinal fibres are less distinctly aggregated into bands than in the colon, being disposed in a more uniform manner, except that, like the circular fibres, they are especially aggregated between the sacculi. The fact that the meso-rectum limits the mobility of the upper and more narrow part of the rectum has led some to locate a third sphincter at this point, but the existence of such an organ has not been generally admitted. Van Buren characterizes it as an organ which "anatomy and physiology had been equally unsuccessful in assigning either certainty of location or certainty of function."1
1 Kelsey, Diseases of the Rectum and Anus, New York, 1882, p. 20.