Pill causes massive urine release
DEAR DR. ROACH: My wife and I were quite puzzled by a recent column, in which you advised a man you diagnosed as suffering from SIADH, the syndrome of inappropriate antidiuretic hormone secretion.
After he was given additional water, then later a saline IV drip to maintain his sodium level, and achieved only marginal results, he was given a single pill of tolvaptan.
He reported that the single pill caused him to “release 6.7 litres of urine”! That’s over 7 quarts, or 14 pints; but the maximum capacity of the human bladder is generally accepted as 2-3 pints. How do you explain this apparent monster discrepancy?
ANSWER: The bladder normally sends a signal when it’s time to empty, at about 150-200 cc (5 to 7 ounces or so), but it can hold maximally perhaps 600 cc (about 1 pint) under normal circumstances. People with larger amounts than that in the bladder generally have a problem with nerve function of the bladder.
In the case of D.L., who had what I thought was SIADH, he released the 6.7 liters overnight.
The kidneys can filter about 40 litres of urine a day, so what he reported was well in the range of normal physiology (although, as I said, I worry about correcting the abnormally low sodium level too fast).
I recall a woman during my training who had a rare complication of pregnancy — peripartum cardiomyopathy, in which the mother’s heart goes into heart failure, unable to squeeze properly. Although we treated her as best we could, one day her heart just started working again suddenly, and she was able to get rid of 20 litres of extra fluid in a day (that’s a 44pound weight loss) without any medication.
It was a remarkable display of the power of a healthy heart and set of kidneys to restore equilibrium. With normal bladder capacity, that would have been over 100 trips to the bathroom!
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.