Kidney stones are notoriously painful and unpleasant. When a large kidney stone passes into the ureter, it results in an acute pain known as renal colic.

Kidney stones, or renal calculi, develop due to the abnormal formation of crystals in the urine. Kidney stones are generally categorized according to their location, with renal lithiasis referring to stones in the kidneys and ureterolithiasis referring to stones in the ureter.

Kidney stones are also categorized according to their chemical composition.  They can be made of calcium, struvite, uric acid and other compounds. About 85% of kidney stones are made of calcium.

Kidney stones occur most frequently in middle-aged and older adults and are more common in men than women. The stones themselves vary in size, with the smallest being invisible to the naked eye and the largest having a diameter exceeding 2.5 centimetres. 

Staghorn kidney stones, which have many branches that resemble antlers, can fill nearly the entire cavity of the renal pelvis (the central funnel in the kidney) and the adjoining tubes.