Screening/Diagnosis
Most episodes of acute diarrhea resolve quickly without antibiotic therapy and with simple dietary modifications. See a doctor if you feel ill, have bloody diarrhea, severe abdominal pain or diarrhea lasting more than 48 hours. In patients with mild acute diarrhea, no laboratory evaluation is needed because the illness generally resolves quickly. Your doctor may perform stool tests for bacteria and parasites if your diarrhea is severe or bloody or if you traveled to an area where infections are common. If you have severe diarrhea, blood tests will be helpful to guide replacement of fluid and electrolytes and minerals such as magnesium, potassium and zinc that can become depleted.
If you have chronic diarrhea, your doctor will want to further assess etiologic factors or complications of diarrhea by obtaining several tests. These can include a blood count to look for anemia and infections, an electrolyte and kidney function panel to assess for electrolyte abnormalities and renal insufficiency, and albumin to assess your nutritional status.
A stool sample may help define the type of diarrhea. The presence of fat, microscopic amounts of blood, and whiteblood cells will help determine if a fatty, inflammatory, or watery diarrhea is present. A bacterial culture and ova/parasite studies of a stool specimen will also help determine if an infectious etiology is present.
Endoscopic examination of the colon with flexible sigmoidoscopy or colonoscopy and upper endoscopy are helpful in detecting the etiology of chronic diarrhea, as this allows direct examination of the bowel mucosa and the ability to obtain biopsies for microscopic evaluation. Double-balloon enteroscopy and capsule endoscopy are sometimes used to examine the mucosa of the small intestine that lies beyond the reach of conventional endoscopes.
Radiographic studies such as an upper GI series or barium enema are not routinely performed in the evaluation of chronic diarrhea, and have largely been replaced by cross-sectional imaging. Ultrasound and CT scan of the abdomen can be helpful to evaluate the bowel, pancreas and other intra-abdominal organs.