The spectrum of disease affecting the anorectal area in children ranges from the common perianal abscess in the infant to rare malformations that present with constipation, bleeding, or other symptoms. This discussion will not cover the problems of imperforate anus, Hirschsprung's disease, or inflammatory bowel disease.

The most common problems concerning the perianal area that bring a child to the attention of a surgeon are perianal abscesses and their resulting fistulae. In contrast to the frequency of anorectal disease in adults, perirectal and ischiorectal abscesses are uncommon in children, except for those with concurrent inflammatory bowel disease. Perianal infection is most often seen in infants between 1 and 15 months of age. The pathophysiology centres on a congenital stenosis of the orifice of an anal gland, which allows stasis and subsequent infection. The abscess then necessitates to the perianal skin, usually within 1 to 2 cm of the dentate line, as an erythematous, fluctuant, painful mass. Although spontaneous drainage occurs surgical incision and drainage is more definitive and may diminish the chance of recurrence.

Fistula formation is a frequent complication of perianal abscess. These fistulae-in-ano track in a radial fashion to the involved gland; they do not follow Goodsall's rule, as in adults. (Goodsall's rule: a fistula opening anterior to a line drawn transversely across the anus will open directly into the anal canal. External openings of fistulae behind this line tend to be multiple and form a horseshoe-type fistula, the opening of which is always in the midline posteriorly.) Surgical excision and secondary healing are almost always successful. A portion of the external sphincter may be traversed, but the internal sphincter is rarely, if ever, affected. Recurrence following excision is rare, but develops in different areas in approximately 10 per cent of infants who have had fistulae excised. These children rarely have an underlying immunological deficiency, and recurrent abscess formation is uncommon after the age of 15 months. If a child presents with a perianal abscess or fistula after the age of 2 years, the clinician should suspect inflammatory bowel disease, sexual abuse, or rare conditions such as chronic granulomatous disease.

Anal fissure is the most common problem in the paediatric age group that results in haematochezia. The clinical history is suggestive of a local problem, with blood being noted after the passage of a large, hard stool. The scybalous stool and associated straining tears the delicate anoderm. Physical examination confirms the diagnosis. Infants are especially susceptible to acute fissures, which require no treatment.

Chronic anal fissures are unusual in children, and their occurrence should raise the suspicion of inflammatory bowel disease. Treatment of older children with anal fissure generally consists of stool softening and warm sitz baths, which help to relax the sphincter spasm that causes a large portion of the discomfort. In general, analgesic ointments fail. Anal dilatation under anaesthesia or a sphincterotomy is rarely necessary in the treatment of a chronic anal fissure in a child.

Haemorrhoids are rarely the cause of a perianal complaint in a child; they are so infrequent in the paediatric population that other sources of the bleeding must be investigated. Complaints of perianal itching and discomfort in a small child are most likely to be secondary to a pinworm (Enterobius vermicularis) infestation. Identification of haemorrhoids in young, otherwise healthy patients should be followed by an ultrasound examination of the liver and portal vein to determine whether portal hypertension is present. In the rare adolescent patient presenting with pain from a thrombosed external haemorrhoid, treatment with a local incision and evacuation of the thrombus is indicated.

Juvenile polyps are a common source of minor and major rectal bleeding. This benign hamartomatous lesion is usually in a rectal location, often solitary, and has been estimated to be present in 3 per cent of the pediatric population. Minor haematochezia may result from ulcerations of the polyp's surface or major bleeding may occur, if the polyp is sheared from the rectal mucosa, exposing an underlying blood vessel in the torn pedicle. These lesions may prolapse through the anus or act as a lead point for true rectal procidentia. Excision by a transanal approach under anaesthesia is indicated. Proctosigmoidoscopy at the time of excision allows the clinician to examine the rectosigmoid for the presence of additional polyps.

Rectal prolapse is a benign process in children usually occurring at the time of toilet training, and can often be effectively treated without surgery. Rectal prolapse may be the initial manifestation of cystic fibrosis, and children with rectal procidentia should undergo a sweat chloride test. An intussusception can manifest itself with prolapse of the intussusceptum from the anus. The diagnosis of intussusception is usually apparent, with a clinical history of crampy abdominal pain and almost immediate recurrence of the apparent prolapse after reduction. The clinician is able to introduce his finger into the rectum besides the suspected procidentia. A rectal polyp may also present at the anal orifice as an apparent prolapse, or it can be the lead point of a rectal prolapse. A careful rectal examination may detect the polyp; barium enema and sigmoidoscopy are indicated if a polyp is suspected but not palpated.

Reduction of the prolapse is the mainstay of treatment. Educating the parents to reduce the mass when first seen can help prevent the oedema, bleeding, and soilage associated with a neglected prolapse. Children with prolapse should be treated with stool softeners and bulk agents in an attempt to avoid straining during bowel movements.

If conservative treatment of rectal prolapse is unsuccessful, the intrarectal, submucosal injection in four separate quadrants of a 5 per cent phenol solution in peanut oil is usually effective. Repeated treatments are occasionally needed, but when they are given more than a 96 per cent success rate can be expected. A requirement for extensive surgery is unusual in children.

Condyloma acuminatum, an infection by the papilloma virus, is rare in children. It is often indicative of sexual abuse, although an infant may also become infected at birth. Initial treatment consists of an application of podophyllin resin, but surgical excision and cauterization are preferable when extensive condylomata must be removed. CO&sub2; laser ablation has been successfully used in children.

Anterior displacement of the anus has been associated with constipation. This constipation generally presents in infancy, when the addition of cereals and cow's milk products generates stool of firmer consistency. The infant strains and holds his breath when attempting to defecate. The normal anus is located midway between the coccyx and the vulva or the perineoscrotal junction. Specific measurements can confirm the displacement. When the constipation is due to misplacement, the anus is typically in an anterior location, close to the vulva or scrotum. Radiographic studies may verify the presence of a posterior rectal shelf and a defaecogram will show ‘bowing’ of the rectum into the levator sling.

Treatment consists of surgical displacement of the anus with either a mucosal flap or a skin flap to the normal position after division of the sphincter. Many patients require repeated anal dilatations for a number of months to prevent stenosis following this procedure. Success is not always guaranteed and the clinician may be balancing constipation against incontinence if too aggressive a displacement and sphincterotomy is attempted.

Pelvic disease may narrow the rectum and hinder the passage of faeces in an infant or young child, who may then present with constipation and urinary retention. Intra-abdominal sacrococcygeal teratoma, neuroblastoma, or neuroenteric cysts may fill the sacral hollow and be palpated as an extrarectal fullness or mass. Imaging studies, defining the mass and the intra-abdominal extension, allow the surgeon to plan the surgical approach for excision appropriately.

Hendren WH. Constipation caused by anterior location of the anus and its surgical correction. J Pediatr Surg 1978; 13: 505–12.

Leape LL. Other disorders of the rectum and anus. In: Welch KJ, Randolph JG, Ravitch MM, O'Neill JA Jr, Rowe MI. eds. Pediatric Surgery. Chicago-London: Year Book Medical Publishers, 1986: 1038–1046.

Wyllie GG. The injection treatment of rectal prolapse. J Pediatr Surg 1979; 14: 62–4.