How long does it take to pass a kidney stone?

Stockbyte/Stockbyte/Getty Images

The pain of a kidney stone can be excruciating, so it's only natural to want to know how long it'll take to pass. The bad news is, it could be anywhere from hours to weeks--but with proper treatment, you can stay comfortable as you wait for it to pass.

To understand this process better, it's good to know what causes kidney stones, why they cause pain, and how to treat them.

Kidney Stones

Kidney stones are hard masses of crystals that form from minerals found in urine. Usually, the chemicals in urine prevent these crystals from forming. Sometimes, though, due to infection, metabolic disorder, diet or simply the luck of the draw, these inhibitory chemicals don't function correctly. Once you've passed your kidney stone, your doctor can examine it and tell you what type it is. This will help you and your doctor formulate a treatment plan: for example, you might be prescribed a special diuretic to prevent stones from forming in the future; you may be told to limit certain foods in your diet; or you may be tested for metabolic issues.

Kidney Stones and the Urinary System

A kidney stone originates in your kidney, hence the name. It travels through the renal pelvis, which is a funnel-like opening between the kidney and the ureter. The ureter is a thin tube leading from each kidney to the bladder. The kidney stone travels through the ureter into the bladder, then out through the urethra, usually in the flow of urine. The kidney stone can get stuck at any point in this journey, which can cause swelling and damage to any part of the urinary system. The longer it's stuck, the more damage it can cause.


Kidney stones can be tiny, moving through the kidneys, ureter, bladder and urethra without the patient even noticing. They can also be golf-ball-sized, in which case they'd require surgery to be removed.

Kidney stones larger than 2-3 mm in diameter stretch the walls of the ureter and renal pelvis (the opening from the kidney to the ureter). These muscles begin to spasm; they're trying to push the kidney stone out. This is what causes pain in your flank, back and stomach. Once the stone has come through the ureter, the pain usually abates. Anywhere from hours to weeks later, the kidney stone will pass, probably during urination. On average, stones take between one and three weeks to pass. Most stones that pass on their own will do so within a month of their first beginning to cause pain.

If the stone doesn't pass within this time, it may be stuck, and could cause infection or other problems if it isn't removed. If you've had a CAT scan or an ultrasound and the stone is larger than about 6mm, your doctor may inform you that the stone is too big to pass on its own and must be removed. One or two out of 10 kidney stones need a doctor's intervention to pass.

Medical Intervention

Doctors can break up large stones with shock wave treatments, and then you'll pass the fragments of your stone. They can also insert a stent to hold your ureter open, which will help stones pass through more quickly. You may need keyhole surgery, or conventional surgery with an abdominal incision, depending on where your stone is stuck.

Home Treatment

If your doctor has told you to let the stone pass on its own, there are several actions you can take to make yourself more comfortable. Take ibuprofen--make sure to ask your doctor how much, and how often you should take it. Sit in a warm bath or use a heating pad on your flank to ease pain. Drink plenty of water--doctors recommend 3,785ml glasses a day for kidney stone sufferers. Make sure you urinate into a strainer or whatever device your doctor has provided for you to use: you need to catch your stone when it passes, so you can give it to your doctor for analysis.