In the child the rectum is relatively larger in its upper part, is nearly straight, almost vertical, and is partly abdominal rather than pelvic. At birth, also, the peritoneal covering descends to the base of the prostate, and, as the other connections are loose, prolapse is frequently met with. The prolapse in such cases is generally partial, consisting only of mucous membrane. Complete prolapse of the whole bowel wall is not very common, and is generally associated with weakness of the pelvic floor, and severe and repeated straining from some cause such as urethral stricture. In such cases it is well to remember that the herniated portion consists of a double layer of bowel, and that a peritoneal pouch frequently exists between the layers in front, into which a portion of small intestine may descend, causing a sudden increase in the size of the swelling.
In the foetus the urinary and rectal systems terminate together in the earlier stages in a common space, or cloaca. Normally the anterior or urogenital section becomes separated from the posterior or rectal portion. The posterior extremity of the bowel does not open on the surface of the body, but a depression from the surface, called the proctodeum, grows down to meet it, and forms the anal portion of the bowel. At first the protodaeum is blind, as is likewise the lower end of the bowel, but finally by absorption of the anal membrane the lumen of the canal is completed. Various deformities are seen affecting the lower end of the rectum. The canal may be patent but narrowed, forming a congenital stricture. The most common condition is that of imperforate anus, where, owing to persistence of the cloacal membrane, a septum exists at the ano-rectal junction. If the proctodeum forms, but the rectum ends unduly high up, the condition is known as absent rectum, while the anus may or may not be present. The rectum may open into the bladder, or a cloaca may persist. Where only a septum exists, it may be perforated by the cautery. Where, on the other hand, the lower rectum is absent, an inguinal colotomy is necessary (Littre's operation).
Two forms of rectal stricture have already been mentioned, the one congenital, and the other fibrous, and generally due to syphilis. Carcinoma, however, constitutes the most, important form of rectal stricture, and, indeed, the rectum is the most frequent site of bowel carcinoma. When situated close to the anus, it may be removed by making a circular incision round the anus, and then separating a sleeve of bowel, and pulling it down from above. As a rule, however, the tumour is situated some 3 or 4 inches above the anus, in a position where its lower extremity may just be touched by the examining finger. In such cases, after a preliminary colotomy, the affected portion of bowel is removed by Kraske's operation, or one of its modifications, in which a median incision is made over the lower portion of the sacrum and coccyx, and extending to about 1 inch from the anus. The tissues on the left side, including the origin of the gluteus maximus, are reflected, as are likewise the attachments of the left sacro-sciatic ligaments, coccygeus and levator ani muscles, to the sacrum and coccyx. The anterior surface of the sacrum is next cleared by the periosteal elevator, the median and lateral sacral arteries and plexus of veins being shelled forward, and then the last two pieces of the sacrum, or at least their left halves, and the whole coccyx, are removed, and the bowel exposed with the haemorrhoidal vessels. It is not advisable to cut away more than the last two pieces of the sacrum, as then the third sacral nerve would be injured (Bardenheuer). The sphincters are supplied by the third and fourth sacral nerves, and the levator ani by the third chiefly, while the bladder is supplied by the second, third, and fourth. Thus, if the third and fourth nerves were destroyed, the sphincter would be paralyzed, and the control of the bladder lost, producing incontinence. If it is necessary to bring down more bowel from above, this may be done by opening into the peritoneum, which so far has been intact, and pulling down. The diseased portion is removed, cutting wide of the disease both above and below, and the healthy ends united. In this operation the anus with the sphincters is preserved intact. The glands lying in front of the sacrum, and in the iliac regions, may be removed if affected, and the portion of sacrum removed may be replaced after the operation. Where the upper portion of the rectum is affected, it may be reached by a combination of peritoneal and sacral routes.
Fissure and fistula frequently affect the anus. Fissure is a narrow crack in the anal skin, extending, perhaps, as far as one of the anal valves, between the columns of Morgagni. It is extremely painful owing to the exposure of one or more nerve terminations, and the constant movements of the rectum with respiration, and of the sphincter. In the more severe cases the sphincter may be overstretched so as temporarily to paralyze it, and the ulcer excised.
Fistula in ano may be produced in much the same manner as the fissure, the mucous membrane about the same site (½ inch above the anus) being damaged by scybalous masses, etc. Organisms thus gain access to the lax submucous layer, and in it they proliferate, and give rise to pus which passes down in this layer and, therefore, on the bowel side of the sphincter, until it reaches the subcutaneous tissues, which, being more resistant, limit the progress of the pus, which at this point forms an abscess. This abscess may immediately point on the surface, and burst, producing the fistula, or, as not infrequently happens, it first bursts into the ischiorectal fossa, which is filled with pus prior to the external bursting, forming an ischio - rectal abscess. Owing to the length and tortuosity of the track, the condition does not heal, but a persistent discharge is kept up, and frequently a small mass of granulation tissue, called a 'sentinel pile,' forms at the external orifice. Treatment consists in overstretching the sphincter, and then carefully passing a director along this superficial and tortuous channel, until the inner opening is reached, and slitting it open, removing diseased track, and packing so as to produce healing by granulations from the bottom. Care must be taken in introducing the director not to introduce it into the ischio-rectal fossa, or to force it along an imaginary fistula. If such be done, the fistula will not be laid open, and the sphincter may be cut.
The lower colon and the rectum possess very considerable absorptive power, which is utilized in feeding by rectal injections of predigested foods. In cases of shock from loss of blood many ounces of saline solution will generally be rapidly absorbed, and it should be remembered when administering alkaloids by rectum that their action so given is only less powerful than when given hypodermically.