Mechanisms, Evaluation, and Management of Chronic Constipation

Abstract

With a worldwide prevalence of 15%, chronic constipation is one of the most frequent gastrointestinal diagnoses made in ambulatory medicine clinics, and is a common source cause for referrals to gastroenterologists and colorectal surgeons in the United States. Symptoms vary among patients; straining, incomplete evacuation, and a sense of anorectal blockage are just as important as decreased stool frequency. Chronic constipation is either a primary disorder (such as normal transit, slow transit, or defecatory disorders) or a secondary one (due to medications or, in rare cases, anatomic alterations). Colonic sensorimotor disturbances and pelvic floor dysfunction (such as defecatory disorders) are the most widely recognized pathogenic mechanisms. Guided by efficacy and cost, management of constipation should begin with dietary fiber supplementation and stimulant and/or osmotic laxatives, as appropriate, followed, if necessary, by intestinal secretagogues and/or prokinetic agents. Peripherally acting μ-opiate antagonists are another option for opioid-induced constipation. Anorectal tests to evaluate for defecatory disorders should be performed in patients who do not respond to over-the-counter agents. Colonic transit, followed if necessary with assessment of colonic motility with manometry and/or a barostat, can identify colonic dysmotility. Defecatory disorders often respond to biofeedback therapy. For specific patients, slow-transit constipation may necessitate a colectomy. No studies have compared inexpensive laxatives with newer drugs with different mechanisms. We review the mechanisms, evaluation, and management of chronic constipation. We discuss the importance of meticulous analyses of patient history and physical examination, advantages and disadvantages of diagnostic testing, guidance for individualized treatment, and management of medically refractory patients.

Figure 1.

Patterns of colonic motor dysfunctions in patients with CC. The pronounced reduction in sigmoid colonic balloon volume indicates a normal tonic response to a meal (D) in a patient with excess colonic stool burden (A). Anorectal tests (not shown) identified a DD. During scintigraphy, colonic transit is usually measured using an isotope coated with a pH-sensitive methacrylate that dissolves in the terminal ileum. In (B), the isotope is in an intact capsule (left) observed in the ascending colon at 24 hours (center panel) and then in the transverse colon at 48 hours (right panel). The geometric center (GC), which is the weighted distribution of the isotope throughout the colon, indicates slow colon transit; normal values are 1.4–3.6 at 24 hours and 2.1–4.9 at 48 hours. In this patient, the colonic manometry (E) depicts considerable phasic pressure activity during the fasting period, increased phasic activity after a meal, and more so after intravenous neostigmine. However, the tonic contractile response to the meal was reduced. (C) shows a patient with delayed colonic transit with normal gastric emptying. In this patient, the colonic manometry (F) reveals sparse phasic pressure activity and tonic or phasic contractile responses to a meal.

Figure 2.

Normal and abnormal anorectal evacuation. Evacuation was recorded by MR imaging (top row) and high-resolution manometry (bottom row). MR imaging shows anorectum filled with gel at rest (A), increased puborectalis indentation during squeeze (B, arrow) and normal relaxation of the puborectalis, perineal descent, opening of the anal canal, and evacuation of ultrasound gel during evacuation (C). In patients with constipation, during evacuation, there is paradoxical contraction of the puborectalis (D, arrow) and exaggerated perineal descent with an enterocele (E, arrow). High-resolution manometry shows anal pressure at rest (F) and increased anal pressure during squeeze (G) compared to rest (F). The white rectangle demarcates the duration of squeeze (G) and evacuation (H–K). Note the increased rectal pressure with anal relaxation during evacuation in a healthy person (H). By contrast during evacuation in constipated patients, note increased rectal pressure with paradoxical anal contraction (I), no change in rectal pressure vs rest (J), and no change in rectal pressure with paradoxical anal contraction (K). Reproduced from Bharucha and Wald, with permission.

Figure 3.

Treatment algorithm for CC.