Also known as infection stones, Struvite kidney stones are usually caused by urinary tract infections. A struvite stone can grow rapidly over a period of weeks and branch out to involve a large part of the inside of the kidney or even all of it. This condition is referred to as staghorn calculi or stone. Struvite stones make up approximately 15-20% of all kidney stones.

Magnesium ammonium phosphate and calcium carbonate apatite is the chemical composition of struvite stones. They occur when urinary tract infections (UTI's) cause enough ammonia which is a key part of the struvite stone, to be made in the urine. Proteus and Klebsiella bacteria are the common causes of urinary tract infections. Struvite stones also thrive best in an elevated urine pH.

Any condition that elevates chronic urinary tract infections with bacteria capable of making ammonia will be a risk factor for struvite stones. One of the major factors for this condition is a situation when a bladder cannot empty completely making the urine stagnant and allowing the growth of bacteria. This is called a neurogenic bladder and can occur with diabetes, strokes and paraplegia.

Struvite stone, unlike other types of kidney stones, don't show many symptoms directly. Patients may experience mild pain or blood in the urine, but they are usually diagnosed as part of a workup for recurring urinary tract infections, usually associated with mild flank pain, blood in the urine, kidney failure, or an incidental finding on a radiology study.

A history of recurrent infections is the first step towards diagnosing struvite kidney stones. A patient with a positive X-ray or CT scan, and urine with a high pH (> 7.0) is a clear indication of Struvite stones. The diagnosis is strongly suspected if you can also find crystals in the urine under a microscope or the stone is a large staghorn.

Struvite stones are known to rapidly grow into large staghorn stones which can lead to overwhelming infection called sepsis or acute kidney failure. Persistent infections can cause kidney scarring over time leading to chronic kidney failure.

Medical therapy is not usually successful and often limited to people who are too sick to undergo a procedure. Shock wave lithotripsy (ESWL) can be used if the stone is reasonably small and in the upper ureter. If it is a staghorn or ESWL fails, percutaneous nephrolithotomy (PNL) is indicated. Sometimes ESWL is used after PNL to deal with leftover fragments. Open surgery is usually reserved for very large or complex stones, a chronically infected and shrunken kidney or for morbid obesity.

The best way to prevent a stone reoccurrence is to completely remove the existing stone and to aggressively treat urinary tract infections. Because calcium stones often accompany struvite stones in most men and some women, they need to be treated as well