Clinical Tip: How to catch a runny stool

November 1, 2004

Collecting stool specimens from an infant who has diarrhea is difficult, especially if the stool is watery and soaks into the diaper before it can be collected.

Collecting stool specimens from an infant who has diarrhea is difficult, especially if the stool is watery and soaks into the diaper before it can be collected. One way around the problem is to line the diaper with clear plastic wrap. When that doesn’t work, I induce stooling in the office and collect the result in a container.

After removing the child's diaper, I place the baby in the supine position and put a sterile urine cup directly under the rectum. Then, I gently stimulate the rectum with a rectal thermometer (nonmercury) or a small, narrow plastic test tube lubricated with sterile lubricant. I take care to insert the thermometer or tube only about 1/2 inch to avoid rupturing the rectum. I can almost always collect more than enough stool for the necessary analyses. I find I have a better chance of success when I use the technique just after the baby has eaten.

On the rare occasion when I fail to obtain a stool sample, I give parents a supply of sterile urine cups and plastic tubes so they can repeat my procedure at home. Usually, parents need little further instruction once they have seen how it’s done. Although collecting stool in the office takes more time, it saves time in the long run because the stools can be processed at the time of the visit—not one or two days later (or not at all).

Douglas G. Olk, MD
Dubuque, Iowa