Q. My infant is constipated — he strains and grunts with bowel movements. How can I treat this?

A. Are his stools of normal consistency and appearance? Does he go regularly and have normal weight gain? If so, he may not have constipation at all. His straining — and even turning red in the face — is likely due to not relaxing his pelvic floor muscles when he tightens his stomach muscles. Not to worry — infants will learn to do it themselves within the first few months of age. Don't use enemas or suppositories for toddlers at this stage; they may cause pain, and can delay this learning process.

Older kids with constipation describe stools that are too small, too big, too infrequent, or painful or difficult to expel. Sometimes this is due to thyroid problems, anal fissures (cuts), intolerance to cow's milk that leads to anal irritation, and so on.

Physical causes of constipation are rare in kids. Abnormal structure of the anorectal area or abnormal development of the nerves of the large intestine (Hirschsprung disease) each occur in only one in 5,000 births. Kids with Hirschsprung disease have constipation from birth, with their first bowel movement often not coming until they are 36 hours old, and they rarely soil their diapers.

For 95 percent of keiki who are constipated, it is a learned behavior, often beginning before age 3 — perhaps they experienced pain or discomfort with bowel movements or are embarrassed to use toilets outside the home, so they delay or ignore urges to defecate. Whatever the reason, as the intestine absorbs water, the stool that remains hardens. The backup of stool causes stomach pain and often an inability to control the overflow of stool. This confuses the child and may anger the parents, who believe the child is intentionally soiling his or her underwear. This only worsens the child's self-esteem.

For infants who are constipated (consult your doctor), try pear, prune or apple juice, corn syrup, or glycerin suppositories.

For children, try a high-fiber diet and increased fluid intake, and make sure they "go" whenever they have the urge. Encourage 5- to 10-minute, unhurried BMs after meals, two to three times a day. Mineral oil, barley malt extract, corn syrup, lactulose, sorbitol, Miralax or even enemas may be needed.

The goal is one to two soft, "mushy" (applesauce to milkshake consistency) stools per day for at least six months, because it takes this long for the abnormally stretched anorectal area to regain its normal sensation, structure and function. Relapses during the first six to 12 months are normal, so be patient.

Dr. Landis Lum is a family-practice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i's John A. Burns School of Medicine. Send questions to Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Hono-lulu, HI 96802; islandlife@hono lulu advertiser.com; or fax 535-8170. This column is not intended to provide medical advice.