What Is a Kidney Stone and How Is It Treated?

It usually starts as a question typed one-handed, often in the middle of the night: why does my side hurt this much? A kidney stone is one of the commonest answers. It's a small, hard lump of minerals that forms inside a kidney — sometimes no bigger than a grain of sand, sometimes noticeably larger — and it tends to stay quiet until it starts to move.

The short video at the top of this page shows one of the ways doctors deal with a stone that won't budge. In just over a minute it walks through ureteroscopy: a thin, lighted tube with a camera is passed through the urethra and bladder into the ureter, the narrow tube draining the kidney, so the stone can be found and dealt with directly. Keep that picture in mind — a lot of the treatment below is about reaching the stone, breaking it up, or helping it on its way out.

What does a kidney stone actually feel like?

That depends on where it is. A stone sitting still in the kidney may cause no pain at all, and some are only found by chance on a scan done for something else. The trouble starts when a stone moves into the ureter and partly blocks the flow of urine. Then the pain can be intense — typically in the side and back, under the ribs, often coming in waves and spreading towards the lower abdomen or groin. You might also notice blood in the urine, needing to pass urine more often, or feeling sick alongside the pain. Fever with that kind of pain is different: it can mean infection behind a blocked tube, and that needs urgent care, not watchful waiting.

How do doctors know it's a stone?

They'll ask where the pain is and how it behaves, examine you, and usually test your urine — blood in it, often invisible, is a common clue. Imaging settles the question: a CT scan is the test most often used to confirm a stone and show its size and position, though ultrasound is also used, particularly when avoiding radiation matters. Size and position matter more than almost anything else, because together they decide what happens next.

Can a stone just pass on its own?

Often, yes — smaller stones frequently do. If yours is small and the pain is manageable, your doctor may suggest waiting for a while, drinking normally, and using pain relief while the stone works its way down and out. You might be asked to strain your urine to catch it, because knowing what a stone is made of helps with preventing the next one. What waiting should never mean is suffering in silence: worsening pain, vomiting that stops you keeping fluids down, fever, or being unable to pass urine are all reasons to get seen promptly.

What if it won't pass — what then?

Then treatment is about removing the stone or breaking it into pieces small enough to pass. The video above shows ureteroscopy, used for stones in the ureter or kidney: once the scope reaches the stone, it can be grasped and removed, or broken up first with a laser. A soft temporary tube called a stent is sometimes left in the ureter afterwards to keep urine flowing while things settle. A different approach, shown in the site's shock wave lithotripsy video, uses focused shock waves from outside the body to crack a stone into fragments that pass naturally over the following days. Larger or stubborn stones occasionally need a procedure through a small opening in the back, and your specialist will explain which option fits your stone's size and position. If stones keep coming back, prevention becomes the real treatment — and that starts with the stone analysis and urine tests your team may arrange. Stones sit in the same urology specialty as several other procedures on this site; our plain-English guide to what a vasectomy is is one example of how those smaller procedures are explained here.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician, researcher, and former Duke faculty.

Educational only — this article is general information about kidney stones and their treatment, not medical advice. Severe flank pain, fever, vomiting, or being unable to pass urine need prompt assessment by your own clinician or an urgent care service.

Frequently Asked Questions

How long does it take for a kidney stone to pass?
It varies a lot with the stone's size and position — smaller stones lower down often pass within days, while larger ones higher up may take longer or not pass at all. Your doctor can give you a timeframe based on your scan and will usually arrange follow-up if it hasn't passed.

What causes kidney stones to form?
They form when minerals in the urine become concentrated enough to crystallise — not drinking enough fluid is a common contributor, and diet, some medical conditions, and family history can play a part too. There are several stone types, which is why analysing a passed stone helps.

Is shock wave lithotripsy the same as surgery?
Not in the usual sense — there are no cuts, because the shock waves are delivered from outside the body. It is still a hospital procedure, usually done with sedation or anaesthesia, and the fragments pass in the urine afterwards.

Can I prevent another kidney stone?
Often you can reduce the risk. The general measures are drinking enough fluid to keep your urine pale, and following any dietary advice based on your stone type. Specific advice depends on why your stones form, so it's worth discussing your own results with your doctor.