 Patients randomized to the intervention arm will be prescribed nitrofurantoin monohydratemacrocrystalline 100 mg twice daily for 7 days prior to PCNL with the final day of prophylactic course being 1 day prior to surgery. Nitrofurantoin monohydratemacrocrystalline is currently indicated for the treatment of acute uncomplicated urinary tract infections. Antibiotics the day of surgery will be a dose of ampicillin IV 2 g and gentamicin IV 5 mgkg within 60 minutes of surgery start time. Patients with penicillin allergy will receive vancomycin IV 1 g instead of ampicillin and patients with gentamicinaminoglycoside allergy will receive ceftriaxone IV 2 g instead of gentamicin. Postoperative antibiotics in the absence of infection will be 24 hours of IV antibiotics. Control patients will receive perioperative ampicillin IV 2 g and gentamicin IV 5 mgkg or vancomycin1 g ceftriaxone 2 g, if indicated as in the intervention arm, but control patients will not be prescribed a course of preoperative oral antibiotics. Central randomization will take place with UCSD as the lead site. Randomization will occur in block randomization in block sizes of 4. 