Do you recommend checking 1,25-hydroxy vitamin D levels in patients with recurrent nephrolithiasis who have hypercalciuria of unknown etiology?  

No, unless they are hypercalcemic or I suspect renal sarcoidosis. Stephen B Erickson, MD

It depends on the degree of the hypercalciuria and whether they also have hypercalcemia and what their PTH concentration is.

No, unless I’m concerned there may be a granulomatous process that is concerting (i.e. sarcoid, lymphoma) as a high 1,25 OH vitamins D in the context of persistent hypercalciuria and recurrent stones may inform my management decision.