Chronic Constipation

An Evidence-Based Review

Lawrence Leung, MBBChir, FRACGP, FRCGP; Taylor Riutta, MD; Jyoti Kotecha, MPA, MRSC; Walter Rosser, MD, MRCGP, FCFP


J Am Board Fam Med. 2011;24(4):436-51. 

In This Article


Diagnostic Approach for Chronic Constipation

History includes (1) duration of complaint; (2) patient's definition of constipation; (3) defecatory frequency; (4) stool consistency; (5) concurrent medication (eg, anticholinergics, diuretics, β-blockers, opiates, iron supplements, calcium channel blockers, antidepressants, acetaminophen, aspirin, and NSAIDs); (6) comorbidities (Parkinson, hypothyroidism); (7) use of supplements or laxatives; and (8) lifestyle enquiry regarding the level of fluid intake, dietary fiber consumption, and daily exercise.

Physical examination includes (1) previous surgical scars; (2) abdominal distension and bowel sounds; (3) palpable mass (fecoliths); (4) inspection of anus for skin tags, hemorrhoids, fissures, hematomas, and prolapse; (5) rectal examination to assess anal reflex, sphincter tone, tenderness, out-pouching (rectocele), or mass in the rectum; (6) gynecological examination to exclude cystoceles or vaginal/uterine prolapse; and (7) full neurological examination to exclude neurological causes.

Investigations include (1) blood tests such as complete blood count, serum glucose, and thyroid and renal functions maybe useful despite limited evidence.[162,163] (2) Colon transit time: Radiograph study with the Sitz marker has been a standard test in distinguishing prolonged transit from normal transit but is unreliable in measuring segmental transit.[164] Scintigraphy with radioisotope is more accurate in measuring transit in different segments of the colon[165] but is more expensive and limited to centers with access to radioisotopes. (3) Anorectal manometry: Pressure exerted by the anal sphincter at rest (normal >80 mm Hg) and with defecatory attempt (normal >180 mm Hg) is measured with a balloon catheter in the anal canal.[166] (4) Balloon expulsion test: Patient is asked to expel a 50 mL rectal balloon (filled with air or water) within 60 seconds; failure to do so suggests pelvic floor dysfunction.[14] (5) Defecography: Serial radiographs of the anorectum are taken when the patient is asked to expel thick barium paste from the rectum. Movement of the pelvic floor and anorectal angle is measured with reference to the sacro-coccygeal line.[14] (6) Dynamic pelvic MRI gives better visualization of the pelvic floor dynamics than does conventional barium defecography and also reveals other anatomic defects contributing to impaired defecation.[167]

Lack of Dietary Fiber, Fluid, and Exercises Will Cause Constipation: How True is This?

Dietary Fiber A prospective cohort of 3327 women found that higher daily fiber intake (20 g/d versus 7 g/d) significantly reduces the likelihood of self-reported constipation.[83] However, other studies have found no such association.[34,84,85] Increasing daily dietary fiber intake may help constipation caused by fiber deficiency,[34,84,86] but one should not assume that fiber deficiency is the main or sole cause.[82,87] Evidence is Level 2C.

Exercise One small, nonplacebo RCT reported that regular exercise decreases constipation as per Rome I criteria,[88] whereas another even smaller study did not show any benefit.[89] Two other cohort studies showed that physical activity significantly decreased the self-reported symptoms in women.[9,83] Evidence is Level 2C.

Fluids A 3-month, prospective study of 21 012 nursing home residents age >65 years found a link between insufficient fluid intake and constipation.[90] One controlled trial showed that higher fluid intake improved chronic constipation in the presence of a high-fiber diet.[91] Other than that there have been no known trials looking at the effects of increased fluids on chronic constipation. Evidence is hence 2C.

Senna, Melanosis Coli, and Colon Cancer: Fact or Myth?

Senna belongs to the genera of anthroquinone-containing herbal laxatives that also embrace aloe, cascara, frangula, and rhubarb. The active ingredients include sennoside A and B. Melanosis coli is a brownish-black discoloration of the colonic epithelium found with chronic use of anthraquinone laxatives,[168] with an association of 73% to 95%.[147,169] Histologically, there is accumulation of lipofuscin-containing macrophages in the lamina propria of the colonic mucosa.[170] Lipofuscin is thought to derive from apoptotic bodies generated by anthroquinone-induced apoptosis of the colonic epithelial cells.[168,171]Melanosis coli can resolve after discontinuation of anthraquinone laxatives.[169] In the last three decades, induction of aberrant crypt foci (ACF) in rat colon has been widely accepted as the pre-neoplastic lesions for modeling colorectal cancer.[172–177] Although 2 studies showed that senna promoted formation of carcinogen-induced ACF in rat colon when given at high doses,[178,179] other studies failed to show any effects of senna in initiating ACF per se or promoting existing ACF.[180,181] In fact, one study even demonstrated a reduction of ACF in rat colon after long-term usage of senna.[182] Similar data in humans are lacking, except for one study that showed increased ACF after a single high dose of senna colonic lavage.[183] A prospective study of 1095 patients reported an increased relative risk of 3.04 for colorectal cancer as a result of anthraquinone laxative abuse.[184] Similarly, a retrospective study of 3049 patients who underwent colonoscopy revealed a higher incidence of Melanosis coli in patients diagnosed with colonic adenomas[184](which are not necessarily malignant). However, subsequent studies failed to demonstrate an association of anthraquinone laxatives with colorectal carcinomas.[180,185–188] Interestingly, one study even hypothesized that the higher rate of adenomas associated with Melanosis coli was due to enhanced ease to spot the white polyps against a dark-colored colon.[189] Taken together, the latest evidence does not support a role of senna in causing colon cancer in rats and humans.[190]


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