Giardiasis

Diagnosis

Your doctor will ask you about your travel history, whether you might have had contact with contaminated water during camping or hiking, and whether your home has well water. If the patient is a child who attends day care, the doctor will ask about any recent outbreaks of diarrhea at the day care center. He or she also will review the patient's symptoms.

The diagnosis is made by testing the stool for Giardia antigen, a protein that is made by G. lamblia parasites, or by identifying G. lamblia cysts or parasites in stool samples. Multiple stool samples may need to be collected since the infection can only be detected in a portion of collected stool samples, even if infection is present. Infrequently, diagnosis may require an inspection of the intestine with a procedure called endoscopy. In this procedure, an instrument called an endoscope is inserted through your mouth into your intestine. An endoscope is a narrow flexible cord-shaped instrument that is equipped with a camera. If necessary, your doctor can use the endoscope to take a small piece of tissue from your small intestine (a biopsy) to be examined in a laboratory.

Expected Duration

The worst symptoms of giardiasis typically last for five to seven days, as long as diagnosis and treatment is not delayed. Symptoms can take as long as several months to completely go away after treatment because the intestine needs to repair itself. It is common to be intolerant to milk and other dairy products that contain lactose for the first few months after a Giardia infection. In some people who are not treated, the infection can cause repeated bouts of abdominal pain and diarrhea for a year or longer.