How do you advise your patients with recurrent nephrolithiasis to avoid consuming more than usual fluid volume on the day of a scheduled 24 hour urine stone risk study?  

I tell them to collect on a day that represents their life as lived - how things are in general. I tell them not to show off. I tell them that if the day does not reflect their usual life, I will be misled and may make mistakes in how I treat them for stone prevention.

The Hawthorne effect is well known to psychologists. It says that people behave differently when they know they are being observed. As the questioner implies, 24 hour urine collections may not reflect the patient’s usual diet and fluid consumption.I emphasize to my patients that I want to see the ...