DEAR DR. DONOHUE: My son, age 43, just had a kidney stone. I understand this is one of the most painful things a person can have. How did he get it? How can he keep from getting another? Should he be on a strict diet? – K.K.

ANSWER: Passing a kidney stone is a most painful experience. Most often the stone gets stuck in the ureter – the drainage tube connecting the kidney to the bladder. Lodged there, the stone brings on abrupt, unremitting, severe pain that often doubles a person over and leads to bouts of vomiting. Once the stone spontaneously passes or is dislodged by any of several methods, the pain stops.

Kidney stones form when the concentration of minerals in the urine exceeds the point where they stay dissolved. It’s like adding spoonful after spoonful of sugar to a glass of iced tea. Eventually, regardless of how hard the tea is stirred, sugar settles to the bottom. With a kidney stone, the mineral is usually calcium coupled with another substance – oxalate.

Men who have had one stone have a 40 percent chance of getting another; women, a 30 percent chance.

Prevention of a stone centers on keeping the urine dilute. If your son drinks two glasses of fluid with each meal and another two glasses at bedtime, he can keep calcium oxalate dissolved. He’ll know he’s drinking enough fluid if his urine is colorless. If it’s not, he needs more fluid. He certainly will need more in hot weather.

You would think that a calcium-restricted diet would be part of a prevention program. It used to be. It no longer is. A low calcium intake enhances oxalate absorption and promotes stone formation. Limiting salt, however, is important. Salt speeds calcium loss into the urine. So does protein, so a low-protein diet might be suggested. Sometimes doctors recommend keeping oxalate foods to a minimum. They include such things as chocolate, spinach, beets, strawberries and walnuts.

DEAR DR. DONOHUE: I read what you had to say about essential tremor, which I have. You omitted an avenue for temporary relief, perhaps for ethical reasons. A cocktail before dinner or wine with dinner makes it possible for me to eat soup and other foods without the embarrassment of shaking. My doctor warned me against driving and using alcohol, so one must be careful. In moderation, with a designated driver, it can be a social blessing. – W.D.

ANSWER: Essential tremor – also called familial tremor, because it runs in families – is the kind of hand trembling that’s at its worst when a person has to make purposeful movements, like spooning soup to the mouth, threading a needle or taking a drink of water. Alcohol almost always abolishes the tremor for a brief period of time. For obvious reasons, alcohol cannot be recommended as a daily treatment, but used in the way you describe, it is usually quite acceptable.

There are other medicines that can often control essential tremor and can be used daily. The beta-blocker medicine propranolol is an example.

DEAR DR. DONOHUE: I am a 79-year-old female who has many sleepless nights. Is melatonin safe to take? How much? And how often can I use it? – S.F.

ANSWER: Melatonin is a product of the pineal gland, a small, mysterious brain gland. The production of melatonin increases in the early evening and continues through the night until early-morning hours. It is involved with the induction and maintenance of sleep. Aging decreases melatonin production, and some suggest that the drop in melatonin accounts for some older people’s insomnia.

The optimal dose of melatonin is not known, nor is the safe length of time for its use. Most authorities suggest limiting the dose to .3 mg to 1 mg per night and to use it only for two weeks.

In the United States, melatonin is not regulated by any federal agency, so people are pretty much on their own if they choose to try it. They should inform their doctors of what they are doing. It might interfere with other prescribed medicines.

DEAR DR. DONOHUE: I am 63 and have to get up two to three times a night to urinate. I have an enlarged prostate gland. If I stop drinking liquids around 6 p.m., will this decrease my nightly trips to the bathroom but increase my chances of getting a kidney stone? – J.H.

ANSWER: An enlarged prostate gland makes it impossible to completely empty the bladder. Therefore, it fills faster and necessitates frequent trips to the bathroom. Standard advice for men with enlarged glands and interrupted sleep because of them is to cut back on the amount of liquid drunk after dinner. Doing so doesn’t measurably increase the risk for kidney stones.

You know, there are medicines that enable men with enlarged glands to more completely empty their bladders. Have you tried any? And there are some office-based procedures that effect a similar result. Of course, there are also standard operations for large glands.

Part of the nighttime urination problem arises from a disruption of normal bladder-emptying cycles. When things are working by the clock, people visit the bathroom more often during the day. With aging, this schedule goes awry, and nighttime becomes the period for more frequent bathroom trips. DDAVP nasal spray can often restore the normal pattern.

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. Readers may also order health newsletters from www.rbmamall.com.