Struvite calculi.

Although calcium oxalate stones are the most common type of calculi found in the United States, struvite or infection stones are quite common and generally pose a difficult treatment dilemma. The presence of urinary infection with a urease-producing organism is necessary for these stones to form. Proteus species account for the majority of infections that cause struvite stones in all age ranges. However, other organisms also produce urease and may be detected in conjunction with struvite calculi. Factors that may predispose one to urinary tract infections increase the likelihood of struvite stone formation. Several options are available for the treatment of existing struvite calculi. Smaller stones may be treated with primary shock-wave lithotripsy, whereas larger stones are more appropriately managed with percutaneous or combination procedures. Medical therapy to prevent recurrent stone formation is also an essential part of the treatment of these patients, as the risk of stone recurrence is extremely high. Antibiotic therapy and urease inhibitors perhaps offer the best form of preventative treatment available today.