Good Medicine: Why Summer Months Are a Boom Time for Kidney Stones

Many urologists refer to summertime as “kidney stone season“: Between Memorial Day and Labor Day, case numbers surge — up to 30% higher than in winter months. Sun exposure and hot, humid temperatures make people sweat, increasing the risk of dehydration. As  urine becomes more concentrated, tiny amounts of mineral and salt crystals — normally flushed out through the bladder — stick together and form stones. Small as a grain of sand or large as a pea, stones are silent until they start to move out of the kidneys and down the ureters: The pain can be excruciating.

According to the National Kidney Foundation, one in 10 Americans will one day develop kidney stones, with men affected twice as often as women. The incidence of stones has doubled since 1970, in part due to the warming climate.

The majority of kidney stones are made of calcium oxalate; others are composed of uric acid, cystine, phosphate, or struvite. In addition to dehydration, risk factors for stones include family history, obesity (metabolic changes increase urinary calcium), and diets high in salt and sugar (both raise urine levels of oxalate and calcium). Certain supplements are linked to stone formation, such as vitamin C at daily doses above 1,000 milligrams, and calcium supplements — including antacids like Tums or Rolaids — exceeding 1,200 milligrams a day. Other risks include medical conditions such as diabetes, hypertension, gout, and osteoporosis.

Sufferers passing a kidney stone typically have colicky pain (coming in waves) that starts in the lower back or flank and radiates to the abdomen or groin. The discomfort is so severe that most victims can’t find a comfortable position. Blood in the urine, fever, and nausea or vomiting is common. 

Kidney stones are diagnosed by computed tomography (CT) of the abdomen and pelvis without contrast —considered the gold standard. Ultrasounds are helpful, too: They are cheaper and radiation-free, but less accurate. Other important tests include urinalysis and bloodwork to rule out infection and to check kidney function and calcium levels. Stone analysis may also be necessary (the patient traps one by urinating through a strainer).

Nearly 80% of the time, stones are small enough to pass on their own. Treatment — based primarily on the stone’s size, type, and location — includes drinking at least three quarts of water a day (12-eight ounce glasses), and prescription medication — to relax the ureters, (like tamsulosin or nifedipine), quell nausea (like ondansetron), and manage pain (like prescription-strength ibuprofen or short-term narcotics). Because the recurrence rate is as high as 50%, a diuretic like hydrochlorothiazide is often recommended to lower the urine’s calcium content.

Stones too large to pass on their own are usually treated with shock wave lithotripsy— high-energy sonic waves powerful enough to break up the stones — and nearly 80% effective. Another option is ureteroscopy: Done under anesthesia, a fiberoptic camera is inserted through the urethra so the specialist can extract the kidney stone. Surgery is necessary in a minority of cases.

To prevent kidney stones, drink an adequate amount of water (six to eight glasses daily); maintain a healthy weight, and limit foods high in salt, sugar, and animal protein. Choose a diet rich in naturally occurring calcium — like yogurt (including soy-based), milk, and kefir. Unlike man-made supplements, these foods inhibit stone formation by binding oxalate in the gut.

If you think you are passing a kidney stone, go to the nearest emergency room. Untreated, they may cause serious kidney damage or infection.

Dr. Mary Jenkins, a contributor to the Herald and member of its board of directors, retired after nearly 40 years as a family practice physician in New York state.