Satish S. C. Rao, M.D., Ph.D., F.R.C.P.
Director, Section of Neurogastroenterology and GI Motility
University of Iowa Hospitals and Clinics
First Published: 2004
Last Revised: March 2004
Peer Review Status: Internally Peer Reviewed
Constipation is a complex of symptoms, the most prominent of which is difficult defecation. In the absence of secondary causes, constipation is regarded as a functional disorder affecting the colon or anorectum or both. At least two subtypes have been recognized, although overlap between the two exists:
Constipation also can be part of the complaints in patients with constipation-predominant irritable bowel syndrome, in whom abdominal pain is a prominent symptom along with altered bowel habit.
Slow transit constipation is defined primarily on the basis of symptoms alone, whereas dyssynergic defecation is defined both on the basis of symptoms and objective physiological criteria.
New facts: The presence of two or more of the following symptoms for at least 12 weeks in the past 12 months are indicative of functional constipation:
Patients with dyssynergic defecation who match the conditions for functional constipation have, in addition, two of the following physiologic criteria:
Constipated patients with or without dyssynergia present with a constellation of symptoms that include a feeling of incomplete evacuation, excessive straining, passage of hard, pellet-like stool, digital disimpaction or vaginal splinting, and a lump-like sensation or blockage in the anal region. Additionally, they may report infrequent defecation, often less than three bowel movements per week, abdominal or anorectal discomfort, pain, or bloating. It must be emphasized that patients may misrepresent their symptoms or feel embarrassed to admit the use of digital maneuvers to disimpact stool or to splint their vagina to facilitate defecation. However, by establishing a trustworthy relationship or through the use of symptom questionnaires or stool diaries, it may be possible to define more precisely the nature of bowel dysfunction in these patients.
A thorough physical examination that includes a detailed neurological examination should be performed to exclude systemic illnesses that may cause constipation. The abdomen must be carefully examined for the presence of stool particularly in the left or right lower quadrant. Anorectal inspection may reveal skin excoriation, skin tags, anal fissure, or hemorrhoids. Perineal sensation and the anocutaneous reflex can be assessed by gently stroking the perineal skin in all four quadrants with the help of a cotton bud or with a blunt needle. Normally, stroking the perianal skin invokes a reflex contraction of the external anal sphincter. If absent, one should suspect neuropathy.
A careful digital rectal examination should be performed to identify the presence of a rectal stricture, stool, or blood in the stool. During digital examination, it is important to ask the patient to bear down as if to defecate. During this maneuver, the examiner should perceive relaxation of the external anal sphincter together with perineal descent. If there is no relaxation, one should suspect functional obstructive or dyssynergic defecation.
Practice: At UI Hospitals and Clinics, a systemic diagnostic process includes several consecutive steps. The first step is to exclude an underlying metabolic or pathologic disorder, because constipation may be the first symptom of many organic conditions, such as colon cancer. A complete blood count, biochemical profile, serum calcium, glucose levels, and thyroid function tests are usually sufficient for screening purposes. If there is a high index of suspicion, serum protein electrophoresis, urine porphyrins, serum parathyroid hormone, and serum cortisol levels may be requested.
A plain x-ray of the abdomen may provide evidence for an excessive amount of stool in the colon. If colonoscopy has not been performed, a barium enema may be useful for excluding colonic pathology. Patients with constipation may have a redundant sigmoid colon, a megacolon, or megarectum. The presence of Hirschsprung's disease also can be detected by barium enema, although manometry and histology are required to confirm the diagnosis.
Evaluation of the distal colonic mucosa through flexible sigmoidoscopy may provide evidence of chronic laxative use or may reveal melanosis coli or other mucosal lesions, such as solitary ulcer syndrome, inflammation, or malignancy. Slow transit constipation may coexist with dyssynergic defecation; thus, assessment of colonic transit together with anorectal function is useful.
Assessment of colonic transit time enables the physician to better understand the rate of stool movement through the colon, because a patient's recall of stool habit is often inaccurate. For routine clinical purposes, a single capsule technique is used. The test is performed by having the patient swallow a single Sitzmarks capsule containing 24 radio opaque markers on day one and by obtaining a plain radiograph of the abdomen on day six. This study may reveal one of three patterns: normal transit defined as fewer than five markers remaining in the colon; slow transit defined as more than five markers scattered throughout the colon; and obstructive defecation pattern defined as the hold-up of more than five markers in the rectosigmoid region with a near normal transit of markers through the rest of the colon. Two-thirds of patients with obstructive or dyssynergic defecation may exhibit a mixed pattern consisting of both slow transit and obstructive delay. Other useful tests are anorectal manometry, balloon expulsion test, defecography, and colonic manometry.
Ideally, patients with slow transit constipation should be treated with a prokinetic agent that selectively stimulates colonic peristalsis. Unfortunately, such an agent is not available for clinical use. Drugs in this category include colchicine, misoprostol, and RU-0211. A novel approach has been the use of neurotrophin, in particular, neurotrophin-3. Neurotrophin promotes the maturation of sensory neurons and modulate synaptic transmission at the neuromuscular junction. A recent four-week, double-blind controlled trial showed that NT-3 improved symptoms, in particular, stool frequency, stool consistency, straining effort, and accelerated colonic transit time in patients with slow transit constipation. Thus, there are several promising compounds for the treatment of constipation. Because of their gut selective prokinetic effect, they may replace the use of pan-gut irritants and laxatives. However, at present, laxatives, such as magnesium compounds and polyethylene glycol, remain the mainstay of therapy.
The treatment of a patient with dyssynergic defecation consists of standard treatment for constipation, including diet, laxatives, timed toilet training, and other measures plus neuromuscular conditioning using biofeedback techniques. The purpose of biofeedback therapy is to restore a normal pattern of defecation by using an instrument-based education program.
Typically, patients are initially taught diaphragmatic breathing techniques to improve their abdominal pushing effort and to synchronize this with anal relaxation. Thereafter, visual or auditory feedback techniques are used to provide input to the patients regarding their performance during attempted defecation maneuvers. The patients' posture and breathing techniques are also corrected using verbal reinforcement techniques. The number of training sessions should be customized to the patients' need. If a patient can demonstrate consistently, i.e., during two consecutive training sessions, a normal pattern of defecation together with an improvement in symptoms associated with difficult defecation, the training sessions may be discontinued.
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