Does your treatment strategy differ when managing patients with recurrent calcium oxalate monohydrate versus calcium oxalate dihydrate stones?

I manage calcium oxalate monohydrate and calcium oxalate dihydrate stones the same way. Based on my laboratory studies of calcium oxalate crystallization, the differentiating feature between these two stone types is likely related to differing inhibitor properties of urinary proteins; forming the dihydrate phase with more inhibitory proteins. We have no standardized measurements or treatments addressing urinary proteins. Consequently, we can only manipulate (lower) calcium oxalate supersaturation, through the usual methods based on diet history and 24-hour urine parameters. These methods include increasing urine volumes, assuring adequate calcium in the diet (1,000-1,500mg per day) from dairy or calcium tablets with meals, reducing salt and...

Good question! And in general, No. Most often, calcium oxalate stones are a mixture of these two stone types; it is unusual they are purely one or the other. However, if I see a pure monohydrate stone, I look harder for the various types of enteric hyperoxaluria: bariatric surgery of the small bowel bypass form, small bowel resection, and partial or complete pancreatectomy (Whipple). Treatment of these disorders centers on dietary oxalate reduction and oral calcium supplementation.

Stephen B. Erickson, MD