Chronic diarrhea differential diagnosis

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Case #1

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Omodamola Aje B.Sc, M.D. [2]

Overview

The differential diagnosis for chronic diarrhea is enormous, with a large number of diagnostic tests available that can be used to evaluate these patients. Classifying the patient with chronic diarrhea into a subcategory helps to direct the diagnostic work-up.

Differential diagnosis

The tree diagram below gives a clear understanding as to how to asses a patient presenting with diarrhea lasting more than 4 weeks.

Adults with chronic diarrhea (> 4 weeks)

Characterize the symptoms: ❑ Onset (congenital, abrupt or gradual) ❑ Pattern (continuous or intermittent) ❑ Duration ❑ Stool characteristics (watery, bloody or fatty) ❑ Fever ❑ Abdominal pain ❑ Weight loss ❑ Fecal incontinence Obtain a detailed history: ❑ Aggravating factors (diet or stress) ❑ Over-the-counter drugs or use of prescription ❑ Previous evaluations (objective records, radiograms or biopsy specimens) ❑ Radiation therapy or surgery ❑ Factitious diarrhea (eating disorders, laxative ingestion, secondary gain or malingering) ❑ Systemic disease (cancer, diabetes, HIV, hyperthyroidism) Elicit the epidemiological factors: ❑ Travel before the onset of illness ❑ Exposure to contaminated food or water ❑ Illness in other family members

Examine the patient: Assess the volume status: ❑ General condition ❑ Thirst ❑ Pulse ❑ Blood pressure ❑ Eyes ❑ Mucosa Perform a general physical exam: ❑ Skin (flushing, rashes or dermatographism) ❑ Oral cavity (ulcers) ❑ Cardiovascular system (murmur) ❑ Respiratory system (wheezing) ❑ Thyroid (mass) ❑ Abdomen (ascites, hepatomegaly, mass or tenderness) ❑ Anorectal (Abscess, blood, fistula or sphincter competence) ❑ Extremities (edema)

Order routine laboratory tests: ❑ CBC and differential ❑ ESR ❑ Serum electrolytes ❑ Total serum protein and albumin ❑ Thyroid function tests ❑ Urinalysis

Start altered diet: ❑ Stop lactose products ❑ Avoid alcohol and high osmolar supplements ❑ Drink 8-10 large glasses of clear fluids (fruit juices, soft drinks etc) ❑ Eat frequent small meals (rice, potato, banana, pastas etc) ❑ Start oral rehydration therapy or intravenous fluids depending on the hydration status

Any specific obvious diagnosis through history and examination?

Yes

No

Chronic infection (outbreaks or endemic areas) ❑ Trial of oral metronidazole 500 mg TID for 5 days for protozoal diarrhea ❑ Oral ciprofloxacin 500 mg BD X 3 days for enteric bacterial diarrhea Medication induced: ❑ Discontinuation of the drug Irritable bowel syndrome (chronic abdominal pain and altered bowel habits in the absence of any organic disorder) ❑ Trial of antispasmodic agents (oral dicyclomine 20 mg QID),OR ❑ TCA's(amitriptyline 10-25 mg OD), OR ❑ SSRI (fluoxetine 20-40 mg OD), OR ❑ Rifaximin

No resolution of the diarrhea

Order stool analysis: ❑ Stool weight ❑ Stool electrolytes and fecal osmotic gap ❑ Stool pH ❑ Fecal occult blood testing ❑ Stool WBC's ❑ Stool fat: Quantitative / Sudan stain ❑ Laxative screen

This management is as per the American Gastroenterological Association guidelines for the evaluation and management of chronic diarrhea.

Additional Management

It is important to differentiate chronic diarrhea based on the kind of diarrhea that is produced. Chronic diarrhea can be subdivided into three major types; watery, fatty, inflammatory. Watery chronic diarrhea can then further be sub-divided into osmotic or secretory diarrhea. Below is a list of differential diagnosis of chronic diarrhea by stool characteristics.

• The stool osmotic gap is a calculation performed to distinguish among different causes of diarrhea.
• 290 − 2 * (stool Na + stool K)
• A low stool osmolic gap can imply secretory diarrhea, while a high gap can imply osmotic diarrhea.

  ❑ Classify diarrhea by the results of the stool analysis:

  Stool osmotic gap >50 mOsm/kg

  Stool osmotic gap <50 mOsm/kg

  Fecal occult blood (+), WBC (+), lactoferrin (+), calprotectin(+)

  Fecal fat (+)

  Osmotic diarrhea

  Secretory diarrhea

  Inflammatory diarrhea

  Fatty diarrhea

  ❑ Check the pH of the stool

  Low pH ❑ Evaluate for carbohydrate malabsorption

  High pH ❑ Evaluate for ingestion of magnesium or antacids ❑ Evaluate for laxative abuse

  1. Exclude infection by any/combination of the following tests: ❑ Stool culture ❑ Microscopic evaluation for ova and parasites ❑ Stool antigen test for Giardia ❑ Small bowel aspirate or breath H2 test to rule out bacterial overgrowth

  1. Exclude structural disease by any/combination of the following tests: ❑ Small bowel radiographs ❑ Sigmoidoscopy or colonoscopy with biopsy ❑ CT abdomen ❑ UGI scopy and small bowel biopsy

  1. Exclude structural disease by any/combination of the following tests ❑ Small bowel radiographs ❑ CT abdomen ❑ Small bowel biopsy and aspirate for quantitative culture

  ❑ Take a careful dietary history ❑ Order breath H2 test (lactose), OR ❑ Order lactase measurement in a mucosal biopsy

  ❑ Order stool alkanization test ❑ Order chromatographic and chemical tests

  2. Exclude structural disease by any/combination of the following tests: ❑ Small bowel radiographs ❑ Sigmoidoscopy or colonoscopy with biopsy ❑ CT abdomen ❑ Biopsy of the proximal small bowel mucosa

  2. Exclude infection by any/combination of the following tests: ❑ Stool culture: Standard Aeromonas, Plesiomonas, Tuberculosis etc ❑ Stool for ova and parasites ❑ Clostridium toxin assay ❑ Other specific test (Serology, ELISA, immunofluorescence to rule out virus and parasites)

  2. Exclude exocrine pancreatic insufficieny by any/combination of the following tests: ❑ Secretin test ❑ Stool chymotrypsin activity ❑ Bentiromide test ❑ Others (D-xylose absorption tests / Schilling test)

  3. Order selective testing: ❑ Cholestyramine test for bile acid diarrhea ❑ Plasma peptides (Gastrin, calcitonin, vasoactive intestinal polypeptide or somatostatin) ❑ Urine (5-hydroxyindole acetic acid, metanephrine or histamine) ❑ Others (TSH, ACTH stimulation test, serum protein electrophoresis or serum immunoglobulins)

  Confirmatory diagnosis

  Yes

  No

  Specific treatment per results and symptomatic treatment

  No response

  Administer empirical therapy ❑ Adequate hydration ❑ Opiates or octreotide

  References

  
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