Renal Colic

Renal colic is the name given for the pain caused by passing a kidney stone. A kidney is found in each flank under the ribs in the lower back. The kidneys play an important role in eliminating waste products from the body. These waste products normally remain dissolved in the urine as it passes from the kidney through its drainage system (calyces, renal pelvis and ureter) into the bladder.

Kidney stones are crystalline particles that form in the urine, often producing pain when they obstruct urine drainage from a kidney. About one in ten Canadians will develop a kidney stone, and of these, half will form more than one over their lifetime. This problem is more common in men than in women, and, it occurs rarely in children.

A kidney stone may remain silently in the kidney for many months or years before being discovered incidentally on imaging studies performed for various reasons. In other cases, a stone may obstruct drainage of urine from a kidney causing pain. This pain can range from a mild and barely noticeable discomfort, to severe cramping or stabbing pain that requires hospitalization for control. Renal colic may wax and wane in severity, coming and going with episodes of pain lasting 20 to 60 minutes. Patients frequently feel the need to move around in order to find a more comfortable position.

The pain occurs on the side of the stone but its precise location depends upon where the stone becomes lodged in the kidney or ureter. The nature and location of the pain may change as the stone migrates down the ureter toward the bladder. Renal colic will often start in the flank (between the ribs and hip) or lower back but it can also be felt in the lower abdomen, groin, genitals or inner thigh. The pain of renal colic may be associated with nausea, vomiting, and frequent or urgent urges to urinate, which may be painful. Blood in the urine (hematuria) occurs frequently with kidney stones. This blood may be visible or microscopic.

The diagnosis of renal colic may be suspected by the description of pain experienced supported by simple blood and urine tests. Some type of medical imaging is necessary to confirm the diagnosis and determine the size and location of the kidney stone. A CT scan is the most commonly used imaging test to diagnose a kidney stone and determine its size and location. Other tests may include ultrasound imaging or IVP (intravenous pyelography), which involves an intravenous injection of “dye” that is excreted into the urine from the kidneys demonstrating their appearance, function and drainage. Many kidney stones can be seen on a simple x-ray of the kidneys, ureter and bladder (KUB). This can be very useful in following the progress of a stone as it passes through the ureter.