The severity of infection stones compared to other stones in the upper urinary tract.

A retrospective study of the case records of 391 adult patients with spontaneously passed or surgically removed concrements from the upper urinary tract during the period 1982-1983 was performed. According to chemical analysis, 66% of the stones were calcium stones, 30% were infection stones, 4% were uric acid/urate stones and 1% were cystine stones. Of the infection stones 12 (10%) were staghorn calculi. The infection stones placed a greater strain on the patients than the calcium stones. Thus, infection stones were significantly more often recurrent stones and required surgery significantly more often than the calcium stones. Only 6% of the patients with infection stones had proved abnormalities predisposing to upper urinary tract infection. Urinary tract infection with a urease-producing microorganism was detected in only 52% of the patients with infection stones. As infection with a urease-producing microorganism is a prerequisite for the formation of infection stones in the urinary tract a careful microbiological investigation to find and treat the infection responsible for the stone formation is mandatory.