eMedicine Specialties > Pediatrics: General Medicine > Gastroenterology

Diarrhea: Differential Diagnoses & Workup

Author: Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children's Hospital
Coauthor(s): Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston; M Akram Tamer, MD, Program Director, Professor, Department of Pediatrics, University of Miami
Contributor Information and Disclosures

Updated: Jan 5, 2009

Differential Diagnoses

Appendicitis
Intussusception
Carcinoid Tumor
Irritable Bowel Syndrome
Congenital Microvillus Atrophy
Malabsorption Syndromes
Crohn Disease
Meckel Diverticulum
Cystic Fibrosis
Protein Intolerance
Giardiasis
Shigella Infection
Hyperthyroidism
Short Bowel Syndrome
Intestinal Enterokinase Deficiency
Ulcerative Colitis
Intestinal Protozoal Diseases

Workup

Laboratory Studies

  • In patients with diarrhea, a stool pH level of 5.5 or less or presence of reducing substances indicates carbohydrate intolerance, which is usually secondary to viral illness and transient in nature.
  • Enteroinvasive infections of the large bowel cause leukocytes, predominantly neutrophils, to be shed into stool. Absence of fecal leukocytes does not eliminate the possibility of enteroinvasive organisms. However, presence of fecal leukocytes eliminates consideration of enterotoxigenic E coli, Vibrio species, and viruses.
  • Examine any exudates found in stool for leukocytes. Such exudates highly suggest colitis (80% positive predictive value). Colitis can be infectious, allergic, or part of inflammatory bowel disease (Crohn disease, ulcerative colitis).
  • Many different culture mediums are used to isolate bacteria. Table 3 lists common bacteria and optimum culture mediums for their growth. A high index of suspicion is needed to choose the appropriate medium.
  • With stool not cultured within 2 hours of collection, refrigerate at 4°C or place in a transport medium. Although stool cultures are useful when positive, yield is low.
  • Always culture stool for Salmonella, Shigella, and Campylobacter organisms and Y enterocolitica in the presence of clinical signs of colitis or if fecal leucocytes are found.
  • Look for C difficile in persons with episodes of diarrhea characterized by colitis and/or blood in the stools. Remember that acute-onset diarrheal episodes associated with C difficile may also occur without a history of antibiotic use.
  • Bloody diarrhea with a history of ground beef ingestion must raise suspicion for enterohemorrhagic E coli. If E coli is found in the stool, determine if the type of E coli is O157:H7. This type of E coli is the most common, but not only, cause of HUS.
  • History of raw seafood ingestion or foreign travel should prompt additional screening for Vibrio and Plesiomonas species.
Table 3. Common Bacteria and Optimum Culture Mediums

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Table
OrganismDetection MethodMicrobiologic Characteristics
Aeromonas speciesBlood agarOxidase-positive flagellated gram-negative bacillus (GNB)
Campylobacter speciesSkirrow agarRapidly motile curved gram-negative rod (GNR); Campylobacter jejuni 90% and Campylobacter coli 5% of infections
C difficileCycloserine-cefoxitin-fructose-egg (CCFE) agar; enzyme immunoassay (EIA) for toxin; latex agglutination (LA) for proteinAnaerobic spore-forming gram-positive rod (GPR); toxin-mediated diarrhea; produces pseudomembranous colitis
C perfringensNone availableAnaerobic spore-forming GPR; toxin-mediated diarrhea
E coliMacConkey eosin-methylene blue (EMB) or Sorbitol-MacConkey (SM) agarLactose-producing GNR
Plesiomonas speciesBlood agarOxidase-positive GNR
Salmonella speciesBlood, MacConkey EMB, xylose-lysine-deoxycholate (XLD), or Hektoen enteric (HE) agarNonlactose non–H2S-producing GNR
OrganismDetection MethodMicrobiologic Characteristics
Aeromonas speciesBlood agarOxidase-positive flagellated gram-negative bacillus (GNB)
Campylobacter speciesSkirrow agarRapidly motile curved gram-negative rod (GNR); Campylobacter jejuni 90% and Campylobacter coli 5% of infections
C difficileCycloserine-cefoxitin-fructose-egg (CCFE) agar; enzyme immunoassay (EIA) for toxin; latex agglutination (LA) for proteinAnaerobic spore-forming gram-positive rod (GPR); toxin-mediated diarrhea; produces pseudomembranous colitis
C perfringensNone availableAnaerobic spore-forming GPR; toxin-mediated diarrhea
E coliMacConkey eosin-methylene blue (EMB) or Sorbitol-MacConkey (SM) agarLactose-producing GNR
Plesiomonas speciesBlood agarOxidase-positive GNR
Salmonella speciesBlood, MacConkey EMB, xylose-lysine-deoxycholate (XLD), or Hektoen enteric (HE) agarNonlactose non–H2S-producing GNR
  • Culture mediums used to isolate bacteria include the following:
    • Blood agar - All aerobic bacteria and yeast; detects cytochrome oxidase production
    • MacConkey EMB agar - Inhibits gram-positive organisms; permits lactose fermentation
    • XLD agar; HE agar - Inhibits gram-positive organisms and nonpathogenic GNB; permits lactose fermentation H2S production
    • Skirrow agar - Selective for Campylobacter species
    • SM agar - Selective for enterohemorrhagic E coli
    • CIN agar - Selective for Y enterocolitica
    • TCBS agar - Selective for Vibrio species
    • CCFE agar - Selective for C difficile
  • Rotavirus antigen can be identified by enzyme immunoassay and latex agglutination assay of the stool. The false-negative rate is approximately 50%, and false-positive results occur, particularly in the presence of blood in the stools.
  • Adenovirus antigens can be detected by enzyme immunoassay. Only serotypes 40 and 41 are able to induce diarrhea.
  • Examination of stools for ova and parasites is best for finding parasites. Perform stool examination every 3 days or every other day.
  • The leukocyte count is usually not elevated in viral-mediated and toxin-mediated diarrhea. Leukocytosis is often but not constantly observed with enteroinvasive bacteria. Shigella organisms cause a marked bandemia with a variable total white blood cell count.
  • At times, a protein-losing enteropathy can be found in patients with extensive inflammation in the course of enteroinvasive intestinal infections (eg, Salmonella species, enteroinvasive E coli). In these circumstances, low serum albumin levels and high fecal alpha1-antitrypsin levels can be found.

Procedures

  • Intestinal biopsy: This procedure may be indicated in the presence of chronic or protracted diarrhea, as well as in cases in which a search for a cause is believed to be mandatory (eg, in patients with acquired immunodeficiency syndrome [AIDS] or patients who are otherwise severely immunocompromised).

More on Diarrhea

Overview: Diarrhea
Differential Diagnoses & Workup: Diarrhea
Treatment & Medication: Diarrhea
Follow-up: Diarrhea
References
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References

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  2. King CK, Glass R, Bresee JS, Duggan C. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. Nov 21 2003;52:1-16. [Medline].

  3. Guarino A, Albano F, Ashkenazi S, et al. European Society for Paediatric Gastroenterology, Hepatology, and Nutrition/European Society for Paediatric Infectious Diseases evidence-based guidelines for the management of acute gastroenteritis in children in Europe: executive summary. J Pediatr Gastroenterol Nutr. May 2008;46(5):619-21. [Medline].

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  6. Abubakar I, Aliyu SH, Arumugam C, Usman NK, Hunter PR. Treatment of cryptosporidiosis in immunocompromised individuals: systematic review and meta-analysis. Br J Clin Pharmacol. Apr 2007;63(4):387-93. [Medline].

  7. Bellemare S, Hartling L, Wiebe N, et al. Oral rehydration versus intravenous therapy for treating dehydration due to gastroenteritis in children: a meta-analysis of randomised controlled trials. BMC Med. Apr 15 2004;2:11. [Medline]. [Full Text].

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  9. Charles MD, Holman RC, Curns AT, et al. Hospitalizations associated with rotavirus gastroenteritis in the United States, 1993-2002. Pediatr Infect Dis J. Jun 2006;25(6):489-93. [Medline].

  10. Coffin SE, Elser J, Marchant C, et al. Impact of acute rotavirus gastroenteritis on pediatric outpatient practices in the United States. Pediatr Infect Dis J. Jul 2006;25(7):584-9. [Medline].

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Further Reading

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Keywords

diarrhea, loose stool, runny stool, fluid stool, acute gastroenteritis, traveler's diarrhea, dysentery, dehydration, childhood diarrhea, malabsorption, malabsorption syndrome, acute-onset diarrhea, inflammatory bowel disease, irritable bowel syndrome, toddler's diarrhea, rotavirus, hemolytic uremic syndrome, HUS, chronic diarrhea, viral diarrhea, rotavirus, adenovirus, astrovirus, liver disease, achlorhydria, hemolytic anemia, sickle cell disease, malaria, agammaglobulinemia, pancreatitis, cystic fibrosis, calicivirus, yersinia enterocolitis, Yersinia enterocolitica, Aeromonas, Shigella, Escherichia coli, E coli, Clostridium, Salmonella, Giardia, Cryptosporidium, Entamoeba

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Contributor Information and Disclosures

Author

Stefano Guandalini, MD, Director, University of Chicago Celiac Disease Program, Section Chief of Gastroenterology, Hepatology and Nutrition; Professor, Department of Pediatrics, University of Chicago Comer Children's Hospital
Stefano Guandalini, MD is a member of the following medical societies: American Gastroenterological Association, European Society for Paediatric Gastroenterology, Hepatology & Nutrition, and North American Society for Pediatric Gastroenterology and Nutrition
Disclosure: Nothing to disclose.

Coauthor(s)

Richard E Frye, MD, PhD, Assistant Professor, Departments of Pediatrics and Neurology, University of Texas Health Science Center at Houston
Richard E Frye, MD, PhD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, Child Neurology Society, and International Neuropsychological Society
Disclosure: Nothing to disclose.

M Akram Tamer, MD, Program Director, Professor, Department of Pediatrics, University of Miami
M Akram Tamer, MD is a member of the following medical societies: American Medical Association and Florida Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Chris A Liacouras, MD, Director of Pediatric Endoscopy, Department of Pediatrics, Division of Gastroenterology and Nutrition, Associate Professor, Children's Hospital of Philadelphia and University of Pennsylvania
Chris A Liacouras, MD is a member of the following medical societies: American Gastroenterological Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

CME Editor

Steven M Schwarz, MD, FAAP, FACN, AGAF, Professor of Pediatrics, State University of New York, Downstate Medical Center College of Medicine; Distinguished Lecturer, New York Medical College, School of Public Health
Steven M Schwarz, MD, FAAP, FACN, AGAF is a member of the following medical societies: American Academy of Pediatrics, American College of Nutrition, American College of Physician Executives, American Gastroenterological Association, American Pediatric Society, Gastroenterology Research Group, New York Academy of Medicine, North American Society for Pediatric Gastroenterology and Nutrition, and Society for Pediatric Research
Disclosure: TAP Pharmaceuticals Honoraria Speaking and teaching; Curemark, LLC Consulting fee Board membership

Chief Editor

Carmen Cuffari, MD, Associate Professor, Department of Pediatrics, Division of Gastroenterology/Nutrition, Johns Hopkins University School of Medicine
Carmen Cuffari, MD is a member of the following medical societies: American College of Gastroenterology, American Gastroenterological Association, North American Society for Pediatric Gastroenterology, Hepatology and Nutrition, and Royal College of Physicians and Surgeons of Canada
Disclosure: Nothing to disclose.

 
 
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