Retroperitoneal Extrusion of a Staghorn Calculus With a Nephrocutaneous Fistula Following a Percutaneous Nephrostomy: A Case Report and Literature Review.

Renal calculi forming a nidus for chronic infection is an established cause of nephrocutaneous fistulation. Although uncommon, extrusion of renal calculi from the kidney can occur on rare occasions. We describe a case of a spontaneously extruded staghorn calculus measuring 3.5 x 2.5 cm from the kidney into the retroperitoneal space resulting from a neglected nephrostomy tube resulting in a nephrocutaneous fistula. We describe the surgical management of the extruded calculus.