Dear Doctor: My husband was in agony recently, and it turned out he was passing a kidney stone. Why does that hurt so much, and what can he do to keep it from happening again?

Dear Reader: It can be shocking, after passing a kidney stone, to see the relatively small size of the object that caused so much pain.

As the name suggests, kidney stones are hard, pebblelike objects formed from the minerals and salts found within the kidney. They can range in size from a grain of sand to a large marble. When stones leave the kidney, they pass into the ureter, which is the duct that carries urine to the bladder. The ureter can’t stretch to accommodate a foreign object, which makes the passage of larger stones difficult — or even impossible. Pain from kidney stones often comes in waves because the ureter goes into spasm to try to force out the stone. When a stone reaches the junction where the ureter meets the bladder, it can cause a sharp, sometimes burning pain during urination.

When a kidney stone blocks the ureter, it causes a backup of urine into the kidney. The resulting pressure causes widespread pain and discomfort, including in the back, belly and groin. The blockage can also lead to infection, which adds fever and chills to the daunting list of symptoms. Nausea, vomiting, cloudy urine, smelly urine, blood in the urine and urinary urgency are also common symptoms. Treatment ranges from hydration and pain meds to make patients more comfortable while passing smaller stones to using shock wave therapy to break larger stones into particles small enough to pass to surgical options for difficult cases.

If you’ve had kidney stones, you can take steps to lessen the odds of a recurrence. First, drink plenty of water throughout the day. Hydrating dilutes your urine, inhibiting the growth of salts and minerals that may aggregate into stones. Also, avoid the use of a sauna, hot tub or steam bath; intensive and extensive workouts; a hot yoga class; and even relaxing on a hot summer day, which can result in sweating and loss of water that, in turn, leads to a drop in urine production. As you drink water during the day, you can add a generous squeeze of lime or lemon, both of which are high in natural citrate, a substance that helps prevent stone formation.

Be aware of your diet. The most common type of kidney stones are calcium stones, which are usually made up of calcium and oxalate, a chemical found in most foods. Foods high in oxalate include beets, spinach, peanuts, sweet potatoes, tea and chocolate.

Red meat, organ meats and shellfish are high in purines, which lead to a higher production of uric acid. This is tied to the formation of uric acid stones, another common type of kidney stone. Fructose, phosphate, salt and alcohol also play a role in kidney stone production. If this all sounds a bit overwhelming, consider asking your doctor to help you create a lifestyle plan to reduce your risk of getting kidney stones.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.

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