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Kidney Stone Prevention

As I entered the exam room, Harry, one of the biggest toughest guys I have as a patient, was on his hands and knees rocking back and forth on the exam table and crying.  This guy is about 6’ 4 inches tall, weighs about 240 pounds and normally wears a huge smile beneath his mountain-man beard.  But a few hours earlier he had experienced sudden brutal left mid back pain.  The pain, with only slight fluctuation, had persisted until now.

Besides helping him get some pain relief, we ordered a type of CT scan that diagnosed a 4 mm stone in his left ureter, the tube that comes down from the left kidney into the bladder.  The good news is that most 4mm stones will pass on their own given adequate pain relief, lots of fluids, and perhaps a type of urinary medicine that increases the likelihood of passage.

In this case, he did indeed pass the stone within a few days without needing surgery or other procedures.  Needless to say, Harry was very interested in whether this was likely to happen again and whether there was anything he could do to prevent it.

Unfortunately, kidney stones are quite common, with 13% of men and 7% of women having at least one attack in their life-time.  Between a third and a half of patients who get one will eventually get another within five years.  If a repeat stone occurs, the chance of further stones becomes even higher.  Often when the CT scan is done, additional stones will be seen sitting painlessly up in the kidneys.  As long as they stay up there they rarely cause symptoms.  But, of course, they indicate a threat of moving down into the narrow ureters where they cause the intense pain of what we call a kidney stone attack.

Harry’s kidney stone was captured in a urine strainer and brought in so that we could send it off for analysis.  Like about 80% of kidney stones, it was a calcium-containing stone, primarily calcium oxalate. The remaining types of stones may be made up of crystals such as uric acid, the key component in gout, or struvite, often connected with urinary infections.

However, as it turns out, more detailed analysis of blood and urine chemistries has not been proven to reduce recurrences.  The good news is that there are some simple measures that are of some benefit.  Not surprisingly, one of these is very good hydration. Specifically, the goal is to drink enough fluids to produce at least two quarts of urine daily.  On a couple of occasions, a person would need to actually pick a day when they could urinate into a jug each time for 24 hours to see if they were achieving this goal.  Studies showed that these folks are able to decrease recurrent stones by 55% over 5 years.  Additionally, avoiding cola types of soft drinks reduced recurrence rates modestly.

If recurrences of kidney stone attacks are happening despite these simple measures, there are a couple of medicines that show a lot of benefit as well.  For example, thiazide diuretics (water pills) have been found to decrease recurrence by 50%, allopurinol by 35% and citrate by 75%.

Anyone who has had a serious kidney stone attack is usually very motivated toward not having another one.  The approach used to be rather complicated, but nowadays includes just a few things.  But these are things worth doing consistently if it allows you to avoid ever again having the kind of pain that makes a rugged man rock on an exam table in tears.

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