evaluated stone culture and urine culture in 1191 patients who underwent PCNL and found that while stone cultures were positive in 72% of patients with struvite stones, urea-splitting organisms accounted for only half of these positive exams. Despite being a major cause of urinary tract infection, only 1.4% of Escherichia coli spp are able to produce urease and are, therefore, not considered a major cause of struvite stone formation ( 1, 6 ). While 100% of Proteus spp, Providencia spp, and Morgenalla morganii spp produce the urea-splitting enzyme, not all Klebsiella spp and Staphylococcus spp are able to produce urease. But not every strain produces the urea-splitting enzyme. Struvite stone formation is associated with bacteria that produce the enzyme urease, including both gram-positive and gram-negative species, such as Proteus, Staphylococcus, Pseudomonas, Providencia, and Klebsiella. Main focus will be on surgical approach and its results. In this article, we aim to discuss major points related to staghorn renal stone, including its pathogenesis, management, and prevention. Significant morbidity and potential mortality of staghorn stones make prompt assessment and treatment mandatory. Factors that predispose patients to struvite stones include female gender, extremes of ages, congenital urinary tract malformations, urinary stasis, urinary diversion, neurogenic bladder, indwelling Foley catheters, distal renal tubular acidosis, medullary sponge kidney, and diabetes mellitus ( 1 - 5 ). Majority of cases are unilateral, but up to 15% of cases may have both kidneys affected ( 4 ). In developed countries its incidence is lower due to early diagnosis and management of renal stones ( 1 - 3 ). In developing countries, 10 to 15% of all urinary calculi are struvite stones and women are twice more frequently affected than men. Most of times they are composed of struvite (magnesium ammonium phosphate), which are linked to recurrent urinary tract infections by urease-producing pathogens. Staghorn renal stones are large kidney stones that fill the renal pelvis and at least one renal calyces. Long-term or short-term antibiotic therapy is recommended and regular control imaging exams and urine culture should be done. The main goals of treatment are stone-free status, infection eradication, and recurrence prevention. Intra-operative high-resolution fluoroscopy and flexible nephroscopy have been described as an alternative for looking at residual fragments and save radiation exposure. To check postoperative stone-free status, computed tomography is the most accurate imaging exam, but ultrasound combined to KUB is an option. Tranexamic acid can be used to avoid bleeding. PCNL can be performed in supine or prone position according to surgeon’s experience. Shockwave lithotripsy and flexible ureteroscopy are useful tools to treat residual fragments that can be left after treatment of complete staghorn renal stone. In cases of impossible percutaneous renal access, anatrophic nephrolithotomy is an alternative. Gold standard surgical technique is the percutaneous nephrolithotomy (PCNL).

Preoperative computed tomography scan and careful evaluation of all urine cultures made prior surgery are essential for a well-planning surgical approach and a right antibiotics choice. Most of staghorn renal stones are composed of struvite (magnesium ammonium phosphate) and are linked to urinary tract infection by urease-producing pathogens.

In this article we aim to discuss the main topics related to staghorn renal stones with focus on surgical approach. Patients with staghorn renal stones are challenging cases, requiring careful preoperative evaluation and close follow-up to avoid stone recurrence.

Staghorn calculus symptoms