Diagnosis

A diagnosis of C. difficile infection is based on the presence of:

• Diarrhea
• Other signs and symptoms of C. difficile infection
• Presence of C. difficile in a stool sample

People who have regular, formed stools should not be tested for C. difficile infection. Recent use of antibiotics is not required for making a diagnosis of C. difficile infection.

Stool tests

If C. difficile infection is suspected, your doctor will order one or more laboratory tests of a stool sample. These tests identify either the toxins or strains of the bacteria that produce toxins.

Colon examination

In rare instances, to help confirm a diagnosis of C. difficile infection and look for alternative causes of your symptoms, your doctor may examine the inside of your colon. This test (flexible sigmoidoscopy or colonoscopy) involves inserting a flexible tube with a small camera on one end into your colon to look for areas of inflammation or abnormal tissue.

Imaging tests

If your doctor is concerned about possible complications of C. difficile infection, he or she may order an abdominal X-ray or a computerized tomography (CT) scan, which provides images of your colon. The scan can detect the presence of complications such as:

• Thickening of the colon wall
• Enlargement of the bowel
• A hole (perforation) in the lining of your colon.