Types of Kidney Stones

Topic Overview

There are four main types of kidney stones.

Calcium stones

Most kidney stones are made of calcium compounds, especially calcium oxalate. Calcium phosphate and other minerals also may be present. Conditions that cause high calcium levels in the body, such as hyperparathyroidism, increase the risk of calcium stones. High levels of oxalate also increase the risk for calcium stones.

Certain medicines may prevent calcium stones.

Uric acid stones

Some kidney stones are made of uric acid, a waste product normally passed out of the body in the urine. You are more likely to have uric acid stones if you have:

• Low urine output.
• A diet high in animal protein, such as red meat.
• An increase in how much alcohol you drink.
• Gout.
• Inflammatory bowel disease.

Certain medicines may prevent or dissolve uric acid stones.

Struvite stones

Some kidney stones are struvite stones. They can also be called infection stones if they occur with kidney or urinary tract infections (UTIs). These types of kidney stones sometimes are also called staghorn calculi if they grow large enough.

Struvite stones can be serious, because they are often large stones and may occur with an infection. Medical treatment, including antibiotics and removal of the stone, is usually needed for struvite stones. Women are affected more than men because of their higher risk of urinary tract infections.

Cystine stones

Less common are kidney stones made of a chemical called cystine. Cystine stones are more likely to occur in people whose families have a condition that results in too much cystine in the urine (cystinuria).

Cystine stones may be prevented or dissolved with medicine. But this may be difficult and not very effective. If a stone causes blockage in the urinary tract or is too large, then it will need to be removed.