Thrombi Within the Urinary Tract May Serve as a Nidus for Rapid Stone Recurrence: A Report of Two Cases.

Nephrolithiasis is increasingly becoming one of the most prevalent and costly urologic conditions in the United States. The most common type of kidney stone in humans is calcium oxalate, accounting for 75% of idiopathic stones in first-time stone formers. Stone formation is typically a gradual process; however, certain factors can accelerate stone development and recurrence. We present two cases of adult white men who were found to have rapidly recurrent symptomatic kidney stones that were ultimately determined to be comprised of an outer mineral shell with an inner core of blood clot. Both patients had a history of nephrolithiasis and recent hematuria. Urine supersaturation values at time of presentation supported formation of kidney stones. Thrombi within the urinary tract can serve as a nidus for formation of multiple types of kidney stones, including calcium oxalate and uric acid stones. Stones arising from such a nidus may exhibit unusually rapid growth.