RECTUM, the lower portion of the large intestine or colon. The term, however, is a misnomer so far as the human anatomy is con cerned, for the bowel adapts itself to the curves of the sacrum and at one point doubles upon itself. The rectum is from six to eight inches long, extending from the sigmoid flexure to the anus, and is narrowest at its two extremities.
The largest and most dilatable portion (am pulla) just above the levator-ani muscle, forms a sort of pocket in which faxes, etc., lodge. The rectum has a mucous coat (membrane), gath ered into transverse folds (Houston's valves), forming compartment-like spaces; a subinucous and a muscular coat; and at the upper portion, where there is little motion, a peritoneal coat (mesentery).
The tendency of specialists is to consider the rectum as only that part of the bowel below the third sacral vertebra and devoid of mesen tery, and to divide it into two portions, the fixed rectum and movable rectum. The rectum is in close opposition with large pelvic vessels and nerves and a portion of the small intestine; also, in the male, with the bladder, urethra and prostate gland, and in the female, with the uterus, vagina and Douglas' cul-de-sac. Its lower portion is surrounded by the hmmor rhoidal plexus of veins. The vessels forming this plexus, as also those of the vaginal and vesico-prostatic plexuses, are very large, fre guently communicate and have many valves. It is in the lower portion of the rectum that hemorrhoids or piles and many other painful affections occur, as blood-vessels and nerves are numerous and the muscles powerful.
Diseases of the Rectum.— These include congenital imperfections. The rectum may even be absent, or partially developed, terminating in a blind pouch; or it may abnormally open into the bladder, vagina, uterus or urethra. These imperfections can be usually remedied by the surgeon.
Threadworms or pinworms frequently in habit the rectum and cause itching about the anus (pruritus ani). They may be destroyed injections of lime-water or a solution of ox gall. Abscesses (caused by blows, perforation, sitting upon cold, damp seats, etc.) may form in the loose areolar tissue about the lower part of the rectum and open externally or into the rectum, leaving a fistulous tract (fistula in ano). Benign tumors, fibroma, papilloma and ade noma and also carcinomatous and sarcomatous tumors may form in the rectum. Haemorrhoids, due to disease or a weakened condition of the hwmorrhoidal veins, are common, especially in persons who are on their feet a large part of the time and who are engaged in seden tary occupation. Hwmorrhoidal affections may be relieved by astringents or by operation. Polypus of the rectum (soft and hard), com paratively frequent in childhood, is a tumor resembling in shape a berry or a pear and hav ing a peduncle. It sometimes bleeds and pro trudes at the anus after stool. It is composed of elongated follicles and a network of small blood-vessels. It may be removed by a ligature or by an appropriate instrument. Prolapsus of the rectum, due to a relaxed state of the sphincter-muscles and the coats of the rectum may be either incomplete or complete, with protrusion from the anus (prolapsus ani). It is
observed generally in young children and women, and is brought on by bearing-down strains. Treatment requires the replacing of the bowel and keeping of it in place, and astringents, caustics and operation are em ployed as may seem advisable. Stricture orthe rectum or narrowing of its calibre may be very limited in extent or may include a con siderable portion of it, and is due usually to malignant or syphilitic ulceration. The symp toms include difficult defecation, more or less purulent and bloody discharges and pain. If not relieved, it affects the general health. Treat ment consists of dilatation with rectal boogies or division of the cicatricial tissue by instru ments (colotomy). Ulceration of the rectum may be due to simple inflammation or to dysen tery, tuberculous disease, syphilis or malignant disease. Symptoms vary with the character of the sores and their location. There are usually discharges of pus, blood and mucus, and some pain and tenesmus. Treatment depends on the nature and extent of the disease and the con stitutional condition of the patient. It includes the keeping of the bowel as quiet and free from fa-cal matter as possible, the use of simple saline aperient and vegetable astringents or nitrate of silver. Fissure of the anus or a tear of its mucous membrane may extend into the rectum or a fissure of the rectum may exist by itself. In either case the fissure is usually produced by the passage of hardened faces and the attendant straining. It is some times obstinate. Treatment calls for regulation of the bowels, dilatation and the application of nitrate of silver or other astringent. Neu ralgia of the rectum is sometimes mistaken (before an examination of the rectum is made) for fissure. Treatment is as in other neuralgias, except when it is caused by pressure of a dis placed coccyx upon sacral nerves. This bone must then be replaced or removed.
Intestinal calculi (enteroliths), gallstones and faecal concretions containing, it may be, fruit-stones or berry-seeds, are occasionally found in the rectum. They give rise to more or less tenderness and abdominal pain, severe and intractable constipation, cold perspiration, vomiting, thready and rapid pulse, etc., and they must be removed. Invagination or in tussusception of the rectum, of thg upper por tion into the lower, as the result of strain and weakened rectal walls, requires surgical aid.
Regular and free movements of the bowels, unattended by straining, are of the greatest im portance in the treatment of most rectal ail ments and preventive of many. The fact that the lower portion of the rectum is capable of holding a large amount of hardened faecal ma terial, while the more liquid matter readily flows by it and out of the body, is not gen erally understood. Consult Lynch, J. M. ( IlDis eases of the Rectum and Colon> (F'hiladelphia 1914) and 'Reference Handbook of the Medi cal Sciences> (New York 1916).