Metabolic risk factors associated with renal Staghorn calculi

INTRODUCTION AND OBJECTIVES: Staghorn calculi are assumed to be related to urinary tract infection and often this is the only factor treated. We sought to determine if any metabolic factors predispose to staghorn stones and predispose to recurrence. METHODS: One hundred patients who had percutaneous renal surgery for staghorn calculi had complete review of their medical records to determine stone composition, urine culture results, findings of metabolic evaluation, rate of residual fragments, and stone recurrence rate. Fortyeight patients had sufficient information for analysis. RESULTS: The mean age of the patients was 52 (55 for men and 48 for women). The most prominent crystal types were as follows: uric acid (UA) in 38% of patients, magnesium ammonium phosphate (MAP) in 21%, calcium oxolate monohydrate (COM) in 16%, carbonate apatite (CAP) in 12%, hydroxyaptite (HAP) in 12% and cystine in 4%. No stone was pure MAP. Only 15% of the patients had a documented urinary tract infection in the pre- or post-operative period. The most common metabolic abnormalities were hyperoxaluria (41 %), hypercalciuria (35%), hypocitraturia (16%) and hyperuricosuria (14%). Altogether, 42 of the 48 patients had a metabolic abnormality, and in 38 patients the abnormality was treatable with medication. CONCLUSIONS: The majority of patients with staghorn calculi have discrete metabolic abnormalities that should be treated in addition to prevention of urinary tract infection. With attention to metabolic evaluation and treatment, recurrent calculi and morbidity can be reduced.