Fecal impaction
Irritable bowel syndrome
Anal diseases
Anal carcinoma
Congenital abnormalities
Protruding internal hemorrhoids
Rectal prolapse
Perianal infections
Fistulae
Injury (e.g. surgical, obstetric, accidental)
Rectal diseases
Rectal carcinoma
Rectal ischemia
Proctitis (e.g. inflammatory bowel disease, radiation therapy, infection)
Neurological diseases
Central nervous system (e.g. cerebrovascular accident, dementia, toxic or metabolic disorders, spinal cord injury or tumors, multiple sclerosis, tabes dorsalis)
Peripheral nervous system (e.g. diabetes, cauda equina lesions)
Miscellaneous
Childbirth injury
Chronic constipation
Descending perineum
Advanced age
Clinical presentation
Partial incontinence is defined as minor soiling and poor flatus control. The elderly and those with internal anal sphincter deficiency, fecal impaction, and rectal prolapse are prone to partial incontinence. Some “leakers” have near normal sphincter pressures and experience soiling secondary to hemorrhoids or fissures. Major incontinence is the frequent loss of large amounts of stool. It is caused by neurological disease, traumatic injury, and surgical damage. Examination may reveal anal deformity, tumors, infections, fistulae, prolapsing hemorrhoids, loss of anal tone, and absence of the anal wink. The anorectal angle and puborectalis function are crudely assessed by palpating this muscle in the posterior midline during rest and voluntary squeeze.
Diagnostic investigation
Several tools assess the mechanisms of continence. Sigmoidoscopy excludes malignancy and proctitis. Anorectal manometry defines resting and maximal anal pressures, rectal compliance, and rectal sensitivity to distension. Advances in manometric technology include ambulatory monitoring and topographic characterization of sphincter pressures. Rectal compliance and sensitivity are quantified using rectal balloon inflation. Miniature probes measure thermal and electrical sensitivity of the anal canal. Electromyography assesses external sphincter and puborectalis muscle activity. Anorectal ultrasound and endoanal MRI measure sphincter muscle thickness and detect muscle defects from trauma or surgical injury. Defecography demonstrates the evacuation of a simulated barium stool and provides static and dynamic measurements of the anorectal angle, pelvic floor, and puborectalis function. Continence is tested by measuring leakage of rectally infused saline or resistance to evacuation of a solid object.
Management
Fecal incontinence often responds to a combination of interventions. Fiber therapy or opiate antidiarrheals are indicated for treating diarrhea. Anticholinergics may blunt the gastrocolonic response and reduce meal-associated incontinence. Fecal impactions are removed with enemas or by manual disimpaction. For individuals who fail these conservative measures, anal biofeedback produces success rates as high as 70% in appropriate patients. With this technique, the patient associates external anal contractions with visual cues such as manometric contractions or electrical discharges on electromyography. Similarly, biofeedback can be used to improve rectal sensation in patients with underlying neuropathy. Conditions that respond poorly to biofeedback therapy include severe organic disease with reduced rectal sensation, irritable bowel syndrome, anterior rectal resection, and prior posterior anal sphincterotomy.
Surgery is generally reserved for patients with major incontinence. Prior anal injury may be repairable with external anal sphincter repair; posterior proctopexy may be performed for complex sphincter injury, pelvic neuropathy, and loss of the normal anorectal angle. Anterior reefing procedures may be useful for women with anterior sphincter defects. Gracilis muscle transposition with or without electrical stimulation may benefit a patient with a destroyed sphincter or a congenital pelvic floor abnormality. Artificial sphincters may be implanted. Recently, sacral nerve stimulators have shown promise in reducing incontinent episodes in a range of clinical conditions. As a last resort, placing a colostomy should be considered.
Pruritus Ani
Clinical presentation
Pruritus ani is an itchy sensation of the anus and perianal skin that may result from perianal disease (fissures, fistulae, hemorrhoids, malignancy) or from residual fecal material. Candida albicans and dermatophyte infections appear as localized erythematous rashes but may also be present on apparently normal skin. Pinworm (Enterobius vermicularis) causes nocturnal pruritus ani in children and in adults exposed to infected children. Scabies (Sarcoptes scabiei
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