['Large or complex calculi within a horseshoe kidney can present a challenge because many cases are associated with other aberrant anatomy. We performed a study to define the outcome of patients with a horseshoe kidney who were treated with percutaneous nephrolithotomy (PNL).', 'From August 1999 to February 2007, 44 PNLs were performed in 35 patients for calculi within a horseshoe kidney. Mean age was 55.4 years. Parameters evaluated to assess the outcomes of PNL included presenting symptoms, stone burden, location of access, stone-free rate, need for secondary intervention, length of stay (LOS), complication rate, stone analysis, and metabolic data.', 'The average stone burden per kidney was 2.59 cm (range 1-6.2 cm). Single percutaneous access was used in 97.7%. Location of the access tract was upper pole (82.2%), interpolar (13.4%), and lower pole (4.4 %). Flexible nephroscopy was performed in all patients. The stone-free rate after primary PNL was 84.1%. Second-look nephroscopy was performed in five kidneys. Overall stone-free rate was 93.2%. Average LOS was 1.92 days (range 1-4 d). Overall complication rate was 14.3%. Stone analysis revealed predominantly calcium stones, and metabolic abnormalities were demonstrated in all patients with 24-hour urine studies.'] Does the presence of horseshoe kidney affect the outcome of percutaneous nephrolithotomy?