RENAL CALCULI [KIDNEY STONES]

Kidney stones are a very common problem. About 12% of men and 5% of women will have at least one kidney stone in their lifetime. Most kidney stones contain calcium. Other substances such as oxalate are necessary to remain in solution in the urine. Stones are typically caused by an imbalance in the urinary system: too little water, too much oxalate, or too much calcium. Rarely are stones related to too much calcium in the blood. There are also other types of stones that can develop, such as uric acid, magnesium ammonium phosphate, or cystine stones.

There are some rare stone types that are inherited in families, although these usually are seen in children. Your physician can determine that you have a stone by a variety of means. It might show on an x-ray of the abdomen, an ultrasound examination, or by intravenous pyelography (IVP, a procedure where dye administered into a vein highlights the "road map" of the kidneys and ureters).

For most patients a stone is an isolated event. The small piece of calcium or uric acid travels down the ureter (the tube connecting kidney and bladder) and causes crampy pain, typically in the flank, that may be severe. Some patients vomit with the discomfort, whereas others are simply aware of an ache in the groin. In some cases there is a history of a previous stone; in others, the stone does not cause many symptoms until it is complicated by infection. In this case, the patient will be quite ill with high fever, chills, pain in the side, and burning on urinating.

The treatment depends on the location and size of the stone. Small stones may pass spontaneously over 24—48 hours; larger stones might require shockwave therapy or rarely surgery to retrieve them. Once the problem has been treated, the main role is in preventing recurrence. About 50% of patients will have another stone within 5 years of the first episode.

The essentials are to maintain a high-volume, dilute urine output to discourage "stagnation" of urine. Keeping the urine as clear as water is a good clue that your fluid intake is sufficient.

As so many stones are formed because of an imbalance of calcium and oxalate, your doctor may treat you with high doses of calcium supplements (e.g., calcium carbonate) or dairy products. This therapy is effective and goes against the common belief that patients with a history of stones should avoid calcium in their diet. Depending on the type of stone you have, your physician may have to use other medications such as hydrochlorothiazide (HCTZ, a diuretic) or allopurinol (a drug that reduces the formation of uric acid, which accounts for about 5% to 15% of stones), depending on the type of stone that is identified by the laboratory.

There are a few side effects of the treatment. Calcium pills can be chalky and hard to swallow, but otherwise are well tolerated. Hydrochlorothiazide is a mild diuretic that can result in impotence (less than 20% of users), high cholesterol levels, high blood calcium levels, low potassium or magnesium, or worsening diabetes. Allopurinol may rarely cause a rash or a lowering of blood cell counts.

If you undergo shockwave treatment, the stone will break up in the ureter and may cause some discomfort as it travels out. Rarely, some patients have had hypertension after this therapy.

• Do drink lots of water every day; 1—2 pints a day is recommended. If you have recurring stones, it's advisable to drink more than this: enough so your urine looks as dilute as water all the time.
• Do take calcium supplements as recommended, to avoid the "imbalance" that might exist.
• Do take the preventive therapy your doctor may prescribe, such as allopurinol or HCTZ.
• Always ask questions regarding your treatment or any side effects you are experiencing.
• Do remember to bring water with you, especially if exercising or working in hot weather.

• Don't get dehydrated.
• Don't forget to choose your food with care. Your physician may suggest a diet rich in calcium and water. Some patients will have an animal protein restriction to avoid making too much uric acid (which can go on to form stones).
• Don't forget the medications prescribed to reduce the risk of further stones forming, such as calcium supplements, HCTZ, or allopurinol.
• Don't use painkillers in excess of the amount prescribed by your health care provider because they can accumulate and make you ill.
• Don't drink too much coffee or tea because they can lead to further dehydration, especially in warm weather.

• Call your doctor if you have fevers or chills, if you are not able to control the pain on the standard treatment, or if you are vomiting and unable to keep food down. You should also call if you are unable to void urine, or if doing so is painful or causes burning. There may be some bleeding with a kidney stone; call the doctor if there is persistent or more blood noticed in the urine.

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