Chronic diarrhea resident survival guide

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

Definition

Diarrhea is defined based upon the frequency, volume, and consistency of stools. It is more commonly defined as more than three loose stools in 24 hours or when the stool weight is more than 200 g per 24 hours containing more than 200 ml fluid per 24 hours. Chronic diarrhea is defined as a decrease in fecal consistency with or without increased stool frequency for more than 4 weeks. Chronic diarrhea may be divided into watery, fatty (malabsorption), and inflammatory (with blood and pus). Watery diarrhea may be subdivided into osmotic (water retention due to poorly absorbed substances), secretory (reduced water absorption), and functional (hypermotility) types. However, not all chronic diarrhea is strictly classified, because some categories overlap.

Causes

Common Causes

Fatty Diarrhea

• Malabsorption syndrome : Bacterial overgrowth, celiac disease, pancreatic insufficiency, short bowel resection, Whipple disease

Inflammatory Diarrhea

• Infection : Amebiasis, Cytomegalovirus, Strongyloides, Tuberculosis, Yersiniosis etc.
• Inflammatory bowel disease
• Ischemic colitis
• Neoplasia : Colon cancer, lymphoma
• Radiation enteritis

Osmotic Diarrhea

• Lactose intolerance
• Other : Antacids, fructose, lactulose, laxatives, magnesium, phosphate, sorbitol ingestion.

Secretory Diarrhea

• Bacterial toxins
• Hormonal : Carcinoid syndrome, diabetes, gastrinoma, hyperthyroidism, medullary carcinoma of thyroid, somatostatinoma, VIPoma
• Irritable bowel syndrome
• Medications : Angiotensin receptor blockers, antibiotics, chemotherapy, colchicine, H2-receptor antagonist, NSAIDs, proton pump inhibitors, SSRIs, laxative (nonosmotic laxatives) etc.
• Postsurgical : Cholecystectomy, gastrectomy, intestinal resection, vagotomy

Management

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

Adults with chronic diarrhea (> 4 weeks)

History ❑ Onset : Congenital / abrupt / gradual ❑ Pattern : Continuous / intermittent ❑ Duration ❑ Epidemiology : Travel / food / water ❑ Stool characteristics : Watery / bloody / fatty ❑ Abdominal pain ❑ Weight loss ❑ Fecal incontinence ❑ Aggravating factors : Diet / stress ❑ Mitigating factors : Diet / over-the-counter drugs / use of prescription ❑ Previous evaluations ❑ Iatrogenic : Medication / radiation therapy / surgery ❑ Factitious diarrhea : Eating disorders / laxative ingestion / malingering ❑ Systemic disease : Cancer, diabetes, HIV, hyperthyroidism, other conditions

Physical Examination ❑ General : Nutrition / vitals / volume status ❑ Skin : Flushing / rashes / dermatographism ❑ CVS : Murmur ❑ RS : Wheeze ❑ Thyroid : Mass ❑ Abdomen : Ascitis / hepatomegaly / mass / tenderness ❑ Anorectal : Abscess / blood / fistula / sphincter competence ❑ Extremities : Edema

Routine laboratory tests ❑ CBC and differential : Anemia / eosinophilia / leucocytosis ❑ ESR ❑ Serum electrolytes ❑ Total serum protein and albumin ❑ Thyroid function tests

Stool analysis ❑ Weight ❑ Stool electrolytes / fecal osmotic gap ❑ Stool pH ❑ Fecal occult blood testing ❑ Stool WBC's : Inflammation ❑ Fat output : Quantitative / Sudan stain ❑ Laxative screen

Categorize diarrhea

Chronic osmotic diarrhea

Chronic secretory diarrhea

Chronic inflammatory diarrhea

Chronic fatty diarrhea

Low pH : Carbohydrate malabsorption

High Mg : Inadvertent ingestion or laxative abuse.

Exclude infection ❑ Stool culture ❑ Stool for ova and parasites ❑ Giardia antigen ❑ Bacterial overgrowth : Small bowel aspirate or breath H2 test

Exclude structural disease ❑ Small bowel radiographs ❑ Sigmoidoscopy or colonoscopy with biopsy ❑ CT abdomen ❑ Small bowel biopsy

Exclude structural disease ❑ Small bowel radiographs ❑ CT abdomen ❑ Small bowel biopsy and aspirate for quantitative culture

Dietary review / breath H2 test (lactose) or lactase assay in biopsy

Exclude structural disease ❑ Small bowel radiographs ❑ Sigmoidoscopy or colonoscopy with biopsy ❑ CT abdomen ❑ Biopsy of the proximal small bowel mucosa

Exclude infection ❑ Stool culture : Standard Aeromonas, Plesiomonas, tuberculosis ❑ Clostridium toxin assay ❑ Other specific test : Virus and parasites

Exclude exocrine pancreatic insufficieny ❑ Secretin test ❑ Stool chymotrypsin activity ❑ Bentiromide test ❑ Others : D-xylose absorption tests / Schilling test

Selective testing ❑ Cholestyramine test for bile acid diarrhea ❑ Plasma peptides : Gastrin / calcitonin / vasoactive intestinal polypeptide / somatostatin ❑ urine : 5-hydroxyindole acetic acid / metanephrine / histamine ❑ Others : TSH / ACTH stimulation / serum protein electrophoresis / serum immunoglobulins

No confirmatory diagnosis / no specific treatment

Emperical therapy ❑ Adequate hydration : ORS / IVF / parental nutrition ❑ Antimicrobial therapy : Depending upon the prevalence of bacterial or protozoal infection in a specific community or situation ❑ Bile acid binding resins : cholestyramine ❑ Opiates / octreotide

Evaluation of Diagnostic Tests

Spot Stool Analysis

Because a 72-hour stool collection is cumbersome, qualitative tests continue to be used in the clinic.

Occult Blood

• A positive test result suggests the presence of inflammatory bowel disease, neoplastic diseases, or celiac sprue or other sprue like syndromes.
• Fecal occult blood positivity can also be associated with laxative-induced diarrhea, pancreatic maldigestion, idiopathic secretory diarrhea, and microscopic colitis.

White Blood Cells

• The standard method of detecting white blood cells (WBCs) in stool is with Wright's staining and microscopy.
• Latex agglutination test is highly sensitive and specific for the detection of neutrophils (lactoferrin) in stool in acute infectious diarrhea and in pseudomembranous colits.
• Calprotectin is a zinc and calcium binding protein that is derived mostly from neutrophils and monocytes and fecal calprotectin may be useful for distinguishing inflammatory from noninflammatory causes of chronic diarrhea.

Sudan Stain for Fat

• Excess stool fat should be evaluated by means of a Sudan stain or by direct measurement.
• The presence of excess fat globules by stain or stool fat excretion >14 g/24 h suggests malabsorption or maldigestion.
• Stool fat concentration of >8% strongly suggests pancreatic exocrine insufficiency.

Fecal Cultures

• In immunocompetent patients, bacterial infections are rarely the cause of chronic diarrhea and routine fecal cultures usually are not obtained in most individuals with chronic diarrhea. However, at least one fecal culture should be performed at some point in the evaluation of these patients, especially under specific environmental conditions suspecting Aeromonas or Pleisiomonas species. The epidemiological clues raising suspicion for the presence of these organisms include consumption of untreated well water and swimming in fresh water ponds and streams.

• In immunocompromised patients, bacterial cultures ought to be part of the initial diagnostic evaluation, as common infectious causes of acute diarrhea, such as Campylobacter or Salmonella, can cause persistent diarrhea.

• Infections with yeast and fungi have been reported as causes of both nosocomial and community-acquired chronic diarrhea, even in immunocompetent individuals. Protozoa and parasites causes are now analyzed by fecal enzyme-linked immunosorbent assay (ELISA) and chronic viral infections are diagnosed from gastrointestinal mucosal biopsy specimens rather than stool samples.

Quantitative Stool Analysis

A 48- or 72-hour quantitative stool collection is useful in the work-up of chronic diarrhea. Full analysis of the collection includes measurement of weight, fat content, osmolality, electrolyte concentrations, magnesium concentration and output, pH, occult blood, and based upon the history fecal chymotrypsin or elastase activity and laxatives. Several days before and during the collection period, the patient should eat a regular diet of moderately high fat content or a fixed diet for some patients to ensure that adequate amounts of fat and calories are consumed. During the collection period, no diagnostic tests should be done that would disturb the normal eating pattern, aggravate diarrhea, diminish diarrhea, add foreign material to the gut, or risk an episode of incontinence. All but essential medications should be avoided, and any antidiarrheal medication begun before the collection period should be held.

Fecal Weight

• Knowledge of stool weight is of direct help in diagnosis and management in some instances. Stool weights greater than 500 g/day are rarely if ever seen in patients with irritable bowel syndrome and stool weights less than 1000 g/day are evidence against pancreatic syndrome.

• Low stool weight in a patient complaining of “severe diarrhea” suggests that incontinence or pain may be the dominant problem.

• Response to fasting such as complete cessation of diarrhea during fasting is strong evidence that the mechanism of diarrhea involves something ingested (nonabsorbable substance or nutrient causing osmotic diarrhea, or unabsorbed fatty acids or laxatives causing secretory diarrhea).

Stool Osmotic Gap

• The osmotic gap is calculated from electrolyte concentrations in stool water by the following formula : 290 - 2([Na+] + [K+]).
• The osmolality of stool within the distal intestine should be used for this calculation rather than the osmolality measured in fecal fluid, because measured fecal osmolality begins to increase in the collection container almost immediately when carbohydrates are converted by bacterial fermentation to osmotically active organic acids.
• Osmotic diarrheas, where electrolytes account for most of stool osmolality, are characterized by osmotic gaps >125 mOsm/kg, whereas secretory diarrheas where nonelectrolytes account for most of the osmolality of stool water, typically have osmotic gaps <50 mOsm/kg. In mixed cases, such in modest carbohydrate malabsorption (in which most of the carbohydrate load is converted to organic anions that obligate the fecal excretion of cations including Na+ and K+), the osmotic gap may lie between 50 and 125.

Fecal pH

• A fecal pH of < 5.3 indicates that carbohydrate malabsorption (such as that associated with lactulose or sorbitol ingestion) is a major cause of diarrhea.
• A pH of > 5.6 argues against carbohydrate malabsorption as the only cause and malabsorption syndrome that involves fecal loss of amino acids and fatty acids in addition to carbohydrate, have a higher fecal pH.

Fecal Fat Concentration and Output

• The upper limit of fecal fat output measured in normal subjects (without diarrhea) ingesting normal amounts of dietary fat is approximately 7 g/day (9% of dietary fat intake)and values more than this signify the presence of steatorrhea.
• A fecal fat concentration of <9.5 g/100 g of stool more likely to be seen in small intestinal malabsorptive syndromes because of the diluting effects of coexisting fluid malabsorption.
• A fecal fat concentrations of ≥9.5 g/100 g of stool were seen in pancreatic and biliary steatorrhea, in which fluid absorption in the small bowel is intact.

References

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