PHILADELPHIA, April 7 - Patients frequently complain of constipation to their physicians, but they and the doctors may be speaking at cross purposes. In a survey of patients and specialist and resident physicians, 50% of the time patient responses disagreed with physicians' answers about what is constipation.
Patients gave just about equal attention to the frequency of bowel movements and the consistency of the stool, but the doctors were much more concerned with frequency when labeling a condition constipation.
Action Points
- When a patient complains of constipation, the first question should not be about frequency, but, "Can you please explain what you mean by constipation?"
"Traditionally even today most textbooks would describe constipation as having a bowel frequency of less than three bowel movements per week. Satish Rao, M.D., Ph.D., a professor of medicine and director of neurogastroenterology and GI motility at the University of Iowa Carver College of Medicine in Iowa City, said.
"But we should change… that is no longer an acceptable definition." When a patient complains of constipation, the first question should not be about frequency, but, "Can you please explain what you mean by constipation?" he said. "Constipation is not one entity but a constellation of symptoms."
Dr. Rao spoke at a symposium titled, "When the Going Gets Tough: Managing Patients with Chronic Constipation," held in conjunction with the annual meeting of the American College of Physicians here.
He said that by the Rome II Criteria constipation-predominant irritable bowel syndrome (IBS-C) and chronic constipation have many symptoms in common, such as fewer than three bowel movements per week; hard, lumpy stools; straining; and a feeling of incomplete defecation. But IBS-C requires symptoms of abdominal pain/discomfort, which are not a primary symptom of chronic constipation. Furthermore, bloating/distension are prominent in IBS-C whereas a sense of anorectal obstruction and sometimes manual maneuvers to defecate are features of chronic constipation.
Chronic constipation can be classified as primary or secondary. Secondary constipation can result from drugs, anal fissure, or colonic obstruction from cancer, among other causes. Once secondary causes are excluded, one is left with primary constipation "which is a neuromuscular disorder of the gut," according to Dr. Rao. Three main subtypes exist, based on physiological tests.
The first subtype is dyssynergic defecation, a relatively new term meaning that defecation mechanisms are uncoordinated or "dyssynergic." Stool comes into the rectum but cannot be expelled fully or at all. Anorectal manometry shows that the rectum and the anus are not working in harmony. In normal defecation the rectum contracts and the anus relaxes to allow stool expulsion. Several patterns of dyssynergia occur: a rise in both rectal and anal pressure; a rise in anal pressure but poor pushing effort in the rectum; and good rectal pressure but with a failure to relax the anal canal.
The second type of primary constipation is slow transit constipation (STC), which occurs when there is neuropathy in the colon and the colon muscle is "too lazy" to push the stool residues along, Dr. Rao said. The pathophysiology of STC is secondary to dyssynergia, neuropathy, myopathy, or a mixed motor/sensory dysfunction. The neuropathic etiology can result from loss of myenteric plexi and of the intestinal pacemaker cells, the interstitial cells of Cajal. The third type of primary constipation is irritable bowel syndromic constipation with pain or discomfort in the presence of normal pelvic floor function and normal transit.
Dr. Rao then focused on IBS-C, the major dysfunction of which is now thought to be a visceral hypersensitivity. As an example, he said if a balloon is inflated in the rectum, IBS-C patients will perceive it at a much lower threshold than control subjects. The problem resides at the receptor level in the gut, in the afferent tract sending the message to the spinal cord, in the relay of the message to the brain, or in the brain's perception of the signal. A study has shown that a major dysfunction may be in the primary somatosensory cortex. Also, descending pathways that modulate sensory perception may be abnormal.
Evaluation of the Patient with Constipation
The evaluation of the patient with constipation begins with a good history: when the problem began, diet, drugs, obstetric history, and any back surgery or injury. Dr. Rao said a diet history is important, and it needs to go beyond fiber intake to include when and how the patient eats, as well as adequate caloric intake. Patients may discuss the defecation response and whether they use digital maneuvers to facilitate defecation, or if they are embarrassed, they may respond to questions in this regard.
Bowel habits such as stool frequency, consistency, and size should be established. "And one of the great ways to look at stool consistency is through this beautiful Bristol stool scale," Dr. Rao exclaimed. "It has changed my practice enormously." Previously, he said he would have to listen to long descriptions of stool transits and how they came out. Now he pulls out a pocket chart, and a patient immediately points to his form of stool from among seven pictures. "Doctor, that's me, that's me, that's me!" he reported patients as saying. "In fact they characterize themselves as stool patterns." The Bristol Stool Form scale is available at various sites on the Internet, including:
The physical examination should involve a detailed abdominal exam to exclude a mass and to detect stool loading, particularly in the left lower quadrant to exclude a mass. After examining the anorectal area for fissures, hemorrhoids, bleeding, and skin excoriation/tags, the physician needs to stroke the anus with a cotton swab in all four quadrants to evoke the ano-cutaneous reflex. If present, it indicates that the sacral neuronal circuitry is intact.
A digital rectal exam can help diagnose pelvic floor dysfunction or dyssynergia. With one finger in the rectum, the physician places the left hand on the patient's abdomen, then instructs the patient to attempt defecation.
"Typically, you should feel tightening of the belly muscles under your left hand, which tells you that they're generating good pushing force," Dr. Rao said. "Then you will feel your finger being ejected, which is good perineal descent and rectal pushing forces. And third and most importantly, you should feel relaxation of the anal sphincter."
If all these signs occur, it is unlikely that the patient has pelvic floor dysfunction or dyssynergia. Otherwise, dyssynergia should be suspected, and manometric evaluation can be used to confirm it. Dr. Rao warned that some coaxing of the patient may be required because the physician is somewhat of a stranger, and patients may be reluctant to attempt defecation lying down or in the bed.
Colonic function can now be easily evaluated using a Sitzmark capsule. This commercially available capsule is filled with 24 radiopaque marker rings. The patient swallows the capsule on day one, and a plane film x-ray is performed on day six (about 120 hours later). Five or fewer markers remaining in the field indicates normal transit; more rings mean slow transit. "This gives you an objective verification of your patient's symptoms because patients' recall of bowel habits is often very poor," he said. Another test is to place a balloon filled with 50 mL of water in the rectum. Most normal individuals can expel it in less than one minute.
Through a systematic review of the literature, Dr. Rao determined that manometry, colon-transit study, and the balloon-expulsion test can be useful and are complementary. But neither barium enema nor colonoscopy is helpful in evaluating constipation. Defecography is generally not helpful but may be in selected cases.