Jackstone: A rare entity of vesical calculus.

Jackstone calculi are urinary tract stones that have a specific appearance resembling toy jacks. They are almost always composed of calcium oxalate dihydrate consist of a dense central core and radiating spicules. They are usually light brown with dark patches and are usually described to occur in the urinary bladder and rarely in the upper urinary tract. Their appearance on plain radiographs and computed tomography in human patients has been described.