Diagnostic approach to constipation

byAbdelwahab Ward, BS Pharm, PharmD - last updated
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INTRODUCTION ã…¡ Is the constipation acute or chronic? If the constipation is acute and there is abdominal pain or vomiting, one must consider the possibility of intestinal obstruction. An examination may disclose an empty rectum, in which case it is more likely complete intestinal obstruction; or there may be some feces in the rectum, in which case there may be incomplete intestinal obstruction. If the constipation is a chronic problem, one should investigate the patient's diet and emotional status and toilet habits over the life span.

          What kind of a diet is the patient on? Many patients today eat on the run, and they eat mostly fast foods, which are devoid of fiber. Frequently, they don't take the time to go to the bathroom. Some patients are on special diets to lose weight or have a fear of gaining weight; therefore, they don't eat well at all. If what the patient labels as constipation is simply infrequent bowel movements, but the bowel movements are normal in consistency, this is not really true constipation.

Does the patient take drugs of any kind? Patients should be questioned first about chronic use of laxatives. Chronic narcotic use can lead to constipation, as can the use of antispasmodics for ulcer or urinary incontinence.

What are the associated symptoms? We have already mentioned that abdominal pain and vomiting may be a sign of acute intestinal obstruction, and occasionally this is a sign of chronic intestinal obstruction. If there is alternating diarrhea and constipation, one must consider the possibility of irritable bowel syndrome or colon carcinoma. 

          Blood in the stool along with painful defecation may indicate hemorrhoids and anal fissure. A person who is suffering from these conditions may delay moving his bowels for fear of the pain that accompanies this situation, and the hard stool that caused the hemorrhoids and anal fissure in the first place perpetuates the condition because it contributes to the constipation. If blood is found in the stool, well mixed with the stool, and defecation is basically painless, then colon carcinoma and diverticulitis must be considered. Blood and mucus in the stool would indicate an irritable bowel syndrome.

What are the findings on physical examination? The finding of an empty rectum indicates an intestinal obstruction. The finding of an abdominal mass or a rectal mass would certainly indicate carcinoma of the colon. Rectal examination may disclose hemorrhoids or anal fissure as causing the chronic constipation and allows one to test the stool for occult blood.

DIAGNOSTIC WORKUP

If the constipation is acute, a flat plate of the abdomen or CT scan and a CBC would be in order to determine if the patient has intestinal obstruction. The workup of chronic constipation begins with eliminating all drugs that may be the cause unless this is contraindicated. The next steps should include stool for occult blood, sigmoidoscopy, barium enema, or a colonoscopy. 
  • A chemistry panel and other diagnostic studies may be necessary to rule out systemic causes of constipation such as diabetes, hypothyroidism, and various conditions associated with hypercalcemia. 
  • If diagnostic tests yield no positive findings, referral to a psychiatrist or a gynecologist may be in order. A trial of a fiber diet may be helpful. At the same time, one should eliminate chronic laxative usage. 
  • Anorectal manometry will help diagnose rectal and anal sphincter dysfunction. Defecography will also help diagnose anorectal dysfunction. A neurologist should be consulted if urinary retention is also a problem. See, algorithm of diagnostic approach to constipation.

REFERENCES

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