DEAR DR. DONOHUE: Recently my son experienced very bad pain from kidney stones. He was told to drink lots of water, take pain medicine and strain his urine to capture the stone when it passed. It did. Where do these kidney stones come from, and how do they form? Will he have a recurrence? – M.C.

Kidney stones form when the urine is saturated with crystals of calcium oxalate, calcium phosphate or uric acid or a few other rare substances. The crystals aggregate to form a stone somewhat in the way stalactites form in a cave. People who form stones do so partly because of the genes they inherited and partly from not drinking enough fluid.

The reason for retrieving the stone is to analyze its composition, because stone composition guides treatment. What I am about to say applies to calcium oxalate stones, the most common kind.

Your son has a 50 percent chance of forming another stone within five years and a 70 percent chance within 10 years unless he adopts a few preventive measures. He must up his daily fluid intake. Stones don’t form when the urine is dilute. Drinking eight 10-ounce glasses of fluid daily is important. All eight glasses need not be only water. He’ll know he’s drinking enough fluid if his urine is pale yellow or colorless. He should cut down on the amount of meat he eats and the amount of salt he uses. Too much of either encourages stone formation.

It would seem logical to go easy on calcium, but most stone formers do not have to watch how much calcium they get. They do need to watch how much oxalate they eat. Oxalate-rich foods include nuts, chocolate, spinach, rhubarb, beets, draft beer, cocoa and tea.

The above steps greatly lessen the chances of repeat stones.

DEAR DR. DONOHUE: I have started to have a walking problem. I recently heard of an ailment, “normal pressure hydrocephalus,” that describes my problem. What can you tell me about it? – T.B.

The brain contains large, hollow caverns through which cerebrospinal fluid flows to nourish and protect the brain’s nerve cells.

Hydrocephalus – literally “water on the brain” – arises when there is an obstruction of fluid flow through the brain caverns.

In infants, whose skull bones are not tightly fused together, hydrocephalus causes head enlargement. In older adults, hydrocephalus enlarges the brain’s caverns but not the head.

Normal pressure hydrocephalus is an enlargement of brain caverns without a rise in fluid pressure. The result is trouble walking, a deterioration of mental sharpness and often a loss of urine control. Patients walk as though their feet were stuck to the floor.

A neurosurgeon can insert a tube into the brain caverns to drain the obstructed fluid out of the brain. That stops further enlargement of the fluid-filled caverns and often achieves a reversal of symptoms.

If you and other readers would like detailed information on either infant or adult hydrocephalus, you can turn to the Hydrocephalus Association, whose number is 1-888-598-3789, or go to its Web site at The association provides people with a wealth of information.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.

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