What Causes Kidney Stones?

What Causes Stones?

Stones form in the kidneys because of continued deposition of some substances that are normally found in urine. Urine has good mechanisms to prevent such deposits, but sometimes these defenses are overcome. A kidney stone may be as tiny as a grain of sand or as big as a pearl. Eight out of ten are less than 2 centimeters in width, but few are as big as golf balls. Some factors that add to your risk of developing stones are:


Symptoms of Stones

A stone may remain in the kidney or start to travel down the urinary tract. Mostly it doesn’t cause symptoms while within the kidney and only gets found during tests done for other reasons. A small one may pass in urine without ever causing trouble. But a fairly large one that gets stuck on its way down can have you tossing in pain. Stones anywhere in the urinary tract can cause:


  • Blood in urine. Blood on a routine urine test is often because of a stone.
  • Repeated urinary tract infections (UTIs)

Here’s more detail on what you can expect from stones at different points in the urinary tract.

Stones within the kidney

  • Generally cause no noticeable symptoms
  • Sometimes a deep flank pain may occur
Stones in the ureter
  • May cause the severe pain that stones are so infamous for (renal colic). It’s a sharp pain that starts suddenly and goes on increasing over the next few hours. You may feel it radiating towards your genital area. You may be very nauseated and even vomit.
  • A stone stuck in the region where the ureter enters the bladder can cause symptoms that look like a UTI, such as:
    • Pain on passing urine
    • Frequent urge to urinate
    • Pain just above your pubic bone
Stones in the bladder
  • A kidney stone that has reached the bladder is unlikely to cause trouble. Mostly it will spontaneously pass in urine.
  • Formation of stones within the bladder is uncommon. If present, a bladder stone can cause UTI-like symptoms such as pain on passing urine, frequent urge to urinate, pain above the pubic bone and occasionally inability to pass urine.

Diagnosis of Stones

The tests that you may undergo during the work-up for a stone are.

  • A urinalysis to check the presence of blood in the urine
  • Blood tests for kidney function, blood count, calcium, phosphate and uric acid levels
  • Urine culture to see the presence of urinary infection
  • One or more imaging tests: A CT scan is the best. It can identify all types of stones and tell their exact location. The other options are an ultrasound,  X-ray ("KUB" or Kidney-Ureter-Bladder X-ray), or an Intravenous Pyelogram (IVP) where a dye is injected in your veins and its movement down your urinary tract is captured on multiple X-rays. But all these methods have some limitations.

When to leave them alone?

Whether a stone should be treated or left alone depends a lot on its size. The availability of advanced techniques makes removal a good option in many cases.


  • Stones less than 3 mm in width will nearly always pass spontaneously
  • Stones up to 5 mm in size can be encouraged to pass with measures like drinking plenty of water.
  • Stones >6 mm have a low chance of passing and often need surgical intervention
  • Stones > 8 mm. have an even lower chance to pass spontaneously anytime soon, and while they are there, they often cause significant symptoms.

However, the decision to treat is always individualized keeping in mind several factors involved such as your age, overall health, whether the stone is causing bothersome symptoms, and very importantly your preference.

Treatment of Stones

If a stone is relatively small and isn’t causing any symptoms, you may be advised to wait and watch. Your doctor can recommend several measures to increase the chances of the stone passing spontaneously.
  • Drinking enough water helps small stones (<5mm) pass spontaneously. You should be drinking enough water to pass at least 2L urine in a day.
  • Some diet changes may be needed depending on the type of stone you have. People with a calcium oxalate stone are advised a diet low in animal protein, sodium, and oxalate. Common oxalate containing foods are chocolate, tea, spinach, asparagus, and nuts. Dairy is allowed in moderate amounts.
  • Medicines to alkalinize the urine and some drugs to reduce stone formation may also be prescribed. Oral antibiotics are needed if stones are associated with infection.
  • If a stone is not expected to pass with these measures, or it is causing serious symptoms one of the following treatments may be advised.
  • Extracorporeal shock wave lithotripsy (ESWL) - A machine is used to send shock waves to break a large kidney stone into smaller stones that can pass spontaneously.
  • Ureteroscopic removal - a long wire with a camera attached to it is inserted into the urethra and passed up through the bladder to the ureter where the stone is located. A trap is used to get hold of the stone and remove it.
  • Percutaneous nephrolithotomy (Tunnel Procedure)- the doctor makes a small cut in the back and makes a narrow tunnel to reach the stone and remove it.
  • Open surgery for stone removal is very rarely needed nowadays.
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