Laboratory Tests and Ancillaries
Gastroenteritis - Bacterial_Diagnostics 1Most patients presenting with acute gastroenteritis do not require laboratory tests. Consider a complete blood count (CBC), blood culture, fecalysis, stool culture and sensitivity, molecular testing (eg polymerase chain reaction [PCR]), serum electrolytes (eg sodium, bicarbonate, potassium), urinalysis, blood urea nitrogen (BUN), and creatinine in patients with evidence of systemic illness, fever, bloody stools, and moderate to severe dehydration. The presence of white and red blood cells on direct microscopy of stool is highly diagnostic of Shigella. If considering giving intravenous (IV) rehydration, electrolytes, glucose, and creatinine may be ordered. Further stool studies are indicated when a patient has a history of traveling abroad or diarrhea that does not improve within 7 days or that occurred in a gastroenteritis outbreak.
Stool Exam
Gastroenteritis - Bacterial_Diagnostics 2A stool exam should be reserved for patients with bloody diarrhea. Stools typical of cholera are typically greenish-yellow, clear, watery, and with little food residue (rice-watery stools).
Stool Microscopy
Stool microscopy may reveal bacteria with darting motility in patients with cholera. No white blood cells (WBC) or red blood cells (RBC) are present in patients with cholera.
Dark Field Microscopy (DFM) and Stool Culture/Sensitivity
Dark field microscopy and stool culture/sensitivity should be performed in both non-endemic and endemic areas, in patients with severe symptoms, high risk for transmission of enteric pathogens, at increased risk for complications, and if there is high suspicion of an outbreak.