Diarrhea

Diarrhea: Excerpt from The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter

Francis G. O’Connor

Diarrhea is one of the most common clinical complaints encountered by primary care providers. Although diarrhea infrequently requires a significant diagnostic evaluation and no more than symptomatic oral rehydration and reassurance, in selected clinical settings (e.g., impoverished, immunocompromised), this ailment can be life-threatening.

Approach

 Identify those individuals with diarrhea who need urgent treatment or an acute diagnostic workup. In more than 90% of patients with acute diarrhea, the illness is mild and self-limited and no laboratory evaluation is necessary. The goal of the initial evaluation of the adult with diarrhea, therefore, is to distinguish these patients from those with more serious disorders.

A. Definition. Diarrhea is best defined as an increase in the fluidity, frequency, and volume of daily stool output, where stool weight is greater than 200 g. Chronic diarrhea is distinguished from acute in that it lasts more than 3 weeks. Infection is the leading cause of acute diarrhea, whereas irritable bowel syndrome is the leading cause of chronic diarrhea.

B. Pathophysiology. Four major mechanisms of diarrhea are seen (1):

 1. Osmotic diarrhea: increased amounts of poorly absorbable, osmotically active solutes in the gut lumen; stool volume decreases with fasting (e.g., laxative abuse, fat malabsorption, Norwalk virus, rotavirus).

 2. Secretory diarrhea: increased chloride and water secretion with or without inhibition of normal active sodium and water absorption; large volume stools with little change with fasting (e.g., toxigenic Escherichia coli, gastrinoma, phenolphthalein).

3. Exudative diarrhea: exudation of mucus, blood, and protein from sites of active inflammation into the bowel lumen; fever, abdominal pain, or both may be present (e.g., Crohn’s disease, psuedomembranous colitis).

4. Abnormal intestinal motility: increased or decreased motility and contact between luminal contents and mucosal surface (e.g., irritable bowel syndrome, thyrotoxicosis).

History

A. General. How long has the diarrhea been present? Most cases of acute diarrhea are secondary to infection (Table 9.1) (2). The overwhelming majority of cases of acute diarrhea are benign and self-limited. Diarrheal illnesses lasting longer than 3 weeks are classified as chronic and should be clinically investigated (Table 9.2) (3,4). Other symptoms to inquire about include associated nausea, vomiting, chills, fever, or abdominal pain. Bloody or melanotic stools and weight loss are red flags that should prompt further diagnostic testing (Chapters 2.13 and 9.11).

B. Acute diarrhea. Has the patient recently traveled, tried new foods, used any medications, or had recent illness? Traveler’s diarrhea commonly begins 3 to 7 days after arrival in a foreign location after exposure to foods or water contaminated with enterotoxigenic Escherichia coli, Salmonella spp., or Giardia spp. Diarrhea that develops within 12 hours of food ingestion is most likely caused by a bacterial preformed toxin. If diarrhea occurs in the setting of a recent course of antibiotic therapy, pseudomembranous colitis caused by Clostridium difficile toxin should be suspected. A thorough medication history includes all products, including over-the-counter agents, alcohol, and caffeine.

 C. Chronic diarrhea. In patients with chronic diarrhea, the history should focus on the characterization of the stools and the pattern of the diarrhea. Diarrhea at night favors an organic cause. Associated periods of constipation can be a clue to irritable bowel syndrome (Chapter 9.3). Is there a family history of diarrhea? Family history can provide clues to a diagnosis of irritable bowel syndrome, inflammatory bowel disease, or a multiple endocrine neoplastic disorder. Concurrent diarrheal illness among family members suggests the possibility of shared pathogens (e.g., Giardia) with a contaminated water source. The history should also detail other medical problems, prior surgeries, and allergies. A sexual history should be sought. Homosexual individuals are at higher risk for exposure to infectious agents, including amebiasis, giardiasis, and shigellosis. In patients with acquired immune deficiency syndrome, infectious agents may include Candida spp., cytomegalovirus, and Cryptosporidium spp. A careful medication history should also screen for laxative abuse.

Physical examination

 A. Focused physical examination. Obtain vital signs (notably temperature) and include orthostatic blood pressure measurements. Assess the patient’s weight and general nutritional status. The abdomen should be examined for bowel sounds, localized tenderness, and organomegaly. A rectal examination may demonstrate a fistula or abscess that can be a clue to Crohn’s disease. Occult or gross blood can indicate an invasive inflammatory diarrheal illness, diverticular disease, or an ischemic bowel.

B. Additional physical examination. The history may lead to a more specific examination (e.g., thyroid for thyrotoxicosis) or a search for lymphadenopathy in an immunocompromised patient.

Testing (5)

 A. Acute diarrhea. Laboratory testing should be reserved for those patients with severe symptoms (e.g., fever, bloody diarrhea, abdominal pain, and dehydration, or symptoms not improving after 5 days) or a comorbid condition. Examination of the stool sample is the most important laboratory test. A single specimen should be submitted for a Wright’s stain for leukocytes, occult blood, Sudan stain for fat, and selected bacterial cultures (Salmonella, Shigella, Campylobacter, and Yersinia organisms). Large numbers of white cells are consistent with inflammatory causes, whereas isolated occult or gross blood may suggest amebiasis, neoplastic disease, vascular disease, or intestinal ischemia. If excess fat is present, malabsorption should be considered (e.g., celiac sprue). Clostridium difficile toxin should be obtained in the elderly and in those with a recent antibiotic history. Tests for ova and parasites on three consecutive specimens should be done in patients with diarrhea that persists for more than 7 to 10 days. In patients where ova and parasite testing is negative and clinical suspicion is high, an enzyme-linked immunosorbent assay test for the Giardia antigen should be considered as well as a wet mount examination of the stool for amebiasis. Sigmoidoscopy is warranted acutely in patients with symptoms of severe proctitis and in patients with suspected C. difficile colitis who appear ill. Rectal swabs for Chlamydia, herpes simplex virus, and gonorrhea may additionally be warranted in sexually active patients with severe proctitis.

B. Chronic diarrhea. Additional tests to be considered include complete blood count, serum electrolytes, liver function tests, calcium, phosphate, albumin, B₁₂, folate, and iron studies to rule out significant abnormalities secondary to the diarrhea, nutritional abnormalities, or hepatobiliary disease. Thyroid studies, serum gastrin, and vasoactive intestinal peptide should be ordered if clinically indicated. Sigmoidoscopy, which allows direct visualization for biopsy and culture, may be helpful in detecting inflammatory bowel disease. Barium studies of the small and large bowel can identify Crohn’s disease, blind loops, celiac sprue, fistulae, and tumors. The stool specimen can be alkalinized for phenolphthalein, consistent with laxative abuse. The presence of steatorrhea warrants a 72-hour collection of stool fat (Chapter 9.12). A gastroenterologist can pursue additional specialized testing, including upper endoscopy with biopsy, breath testing for malabsorption, and pancreatic function testing.

Diagnostic assessment

A careful history helps to classify the diarrhea, provides clinical clues for selected diagnostic testing, and aids in risk stratifying the patient. Comorbid diseases and associated symptoms increase the urgency for diagnostic workup and management (e.g., fever, symptoms > 5 days, bloody diarrhea, known exposures, weight loss). Abnormal vital signs or bloody diarrhea identify patients at higher risk who require early therapeutic intervention. Although most diarrhea is benign and self-limited, a thorough history, focused physical examination, and directed laboratory testing will identify those cases requiring early diagnostic evaluation, aggressive management, or referral.

References

1. Kroser JA, Metz DC. Evaluation of the adult patient with diarrhea. Primary Care 1996;23(3):629–647.

2. Blacklow NR, Greenberg HB. Viral gastroenteritis. N Engl J Med 1991;325(4):
252–264.

3. Donowitz M, Kokke FT, Saidi R. Evaluation of patients with chronic diarrhea. N Engl J Med 1995;332(11):725–729.

4. Norris TE. Lower gastrointestinal problems. Monograph, edition No. 198. Home Study Self-Assessment program. Kansas City, Mo: American Academy of Family Physicians, November 1995.

5. Kearney DJ, McQuaid KR. Approach to the patient with gastrointestinal disorders. In: Grendell JH, ed. Current diagnosis and treatment in gastroenterology. Norwalk, CT: Appleton & Lange, 1996.

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Book Source Details

• Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
• Author(s): Robert B. Taylor (editor)
• Year of Publication: 2000
• Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.

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More About This Book: Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter Authors: Robert B. Taylor (editor) Publisher: Lippincott Williams & Wilkins Copyright: 2000 ISBN: 0-78172-094-X

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