Renal obstruction from persistent struvite stone matrix: a complication of extracorporeal shock wave lithotripsy.

Struvite calculi occurring in patients with chronic urinary tract infections consist of an inorganic component of magnesium ammonium phosphate crystals and an underlying organic mucopolysaccharide matrix. Shock waves used to destroy these stones during extracorporeal shock wave lithotripsy (ESWL) therapy may affect the inorganic and organic components of the stone differently. In a 26-year-old woman, renal obstruction resulted from retained struvite stone matrix after ESWL therapy.