Kidney stones, also known as nephrolithiases, urolithiases or renal calculi, are solid accretions (crystals) of dissolved minerals in urine found inside the kidneys or ureters. They vary in size from as small as a grain of sand to as large as a golf ball. Kidney stones typically leave the body in the urine stream; if they grow relatively large before passing (on the order of millimeters), obstruction of a ureter and distention with urine can cause severe pain most commonly felt in the flank, lower abdomen and groin. Kidney stones are unrelated to gallstones.
Kidney stones are usually asymptomatic until they obstruct the flow of urine. Symptoms can include acute flank pain (renal colic), nausea and vomiting, restlessness, dull pain, hematuria, and possibly fever if infection is present. Acute renal colic is described as one of the worst types of pain that a patient can suffer. Note that the pain is generally due to the stone's presence in the ureter, and not—as is commonly believed—the urethra and lower genitals.
Some patients have no symptoms until their urine turns bloody—this may be the first symptom of a kidney stone. The amount of blood may not be sufficient to be seen, and thus the first warning can be microscopic hematuria, when red blood cells are found in the microscopic study of a urine sample, during a routine medical test.
Stones less than 5 mm in size usually will pass spontaneously, with diclofenac usually providing effective pain management. However the majority of stones greater than 6 mm will require some form of intervention, especially so if the stone is stuck causing obstruction and infection of the urinary tract.
In many cases non-invasive Extracorporeal Shock Wave Lithotripsy may be used. Otherwise some form of invasive procedure is required; with approaches including retrograde ureteral, percutaneous nephrolithotomy or open surgery, and using laser, ultrasonic and mechanical (pneumatic, shock-wave) forms of energy to fragment stones.