Kidney stones

A kidney stone is a small, solid mass that can form in the kidneys and can move into other parts of the urinary tract. Large kidney stones can get stuck in the thin tubes, called the ureters, that connect each kidney to the bladder. This can cause extreme pain in the side and back, below the ribs. The pain can come in waves and may sometimes spread to the groin.

Kidney stones are usually treated with pain medication and by drinking lots of water to help its pass through the urinary tract. Large kidney stones that are not able to pass naturally may need to be removed with surgery or other techniques.

Kidney stones may be prevented by drinking plenty of water and changing some of the foods you eat. Certain types of medication can help prevent the formation of specific types of kidney stones. If you develop and pass a kidney stone, collecting it from the urine can help to find out the stone type, and may help to prevent them in the future.

Causes

The kidneys are organs that are responsible for filtering excess fluid and waste from the blood, and the by-product of this is urine. Kidney stones can form when there is a high concentration of salts and minerals in the urine. The salts and minerals form crystals, which then group together to form a kidney stone.

Some stones can stay in the kidney without causing any symptoms. However, if the stones move out of the kidney into the ureter, they can become lodged if they are large enough. When this happens, the stone can block the movement of urine causing dilation of the ureter. The muscular wall of the ureter can also contract against the obstructing stone causing severe pain.

A kidney stone in the ureter can cause a strong pain and a blockage with dilation of the ureter. 

Types

Kidney stones can be divided into several different types, depending on what they are made of:

Calcium stones

Calcium stones are the most common type of kidney stone and can form if there is a high amount of calcium in the urine. They are sometimes called calcium oxalate or calcium phosphate stones, depending on the other substances that make up the stone.

Struvite stones

Struvite stones can form very quickly and can often be very large. They usually occur as a result of a urinary tract infection (UTI).

Uric acid stones

Uric acid stones form when the urine contains too much uric acid. Some people are more likely to develop uric acid stones because of genes inherited from their parents.

Cystine stones

Cystine stones are made from an amino acid called cysteine. Cystine stones are caused by a rare condition called cystinuria, which is inherited from your parents.

Signs and symptoms

If you have a kidney stone you might not experience any symptoms until it starts to move down through the urinary tract. Pain is the main symptom when this occurs and it is usually felt in the side and back, below the ribs. The pain can often come in waves and may spread to the groin. Some of the other symptoms you might experience if you have a kidney stone include:

• Nausea and vomiting;
• Pain when passing urine;
• Blood in the urine;
• A feeling of needing to urinate often, and;
• Cloudy or smelly urine.

Methods for diagnosis

Your doctor may identify that you have a kidney stone based on your presenting symptoms. To help confirm the diagnosis, your doctor will take your full medical history and perform a physical examination.

You may have a blood test to measure your kidney function, as well as your calcium and uric acid levels. When calcium and uric acid are in high concentration they can form kidney stones. Your doctor may also collect a sample of your urine to see if you have any blood in your urine or infection in your urinary tract, which can be associated with kidney stones.

Imaging techniques such as X-rays, ultrasounds and computerised tomography (CT) scans can be used to look for kidney stones and to check if they are stuck in the urinary tract.

Stones that have been passed may be collected and sent to a laboratory for analysis. Finding out what type of stone you had may provide important information about how future stones can be prevented.

Types of treatment

Small kidney stones are usually treated with pain-relief medication such as ibuprofen and by drinking lots of water, which may help the stones to pass in the urine. In some cases, large kidney stones may need additional treatments.

Medication

If you are having trouble passing a kidney stone, your doctor may prescribe medications, such as tamulosin, to help relax the muscle in the ureter, so that the stone can pass through faster. You may also be prescribed stronger pain-relief medication, such as morphine or fentanyl, if you are experiencing extreme pain.

Surgical procedures

Some of the procedures that can help to treat large kidney stones include:

Extracorporeal shock wave lithotripsy

Extracorporeal shock wave lithotripsy is a procedure that uses shock waves to shatter the stones into smaller pieces, which can then be passed in the urine. This procedure can be uncomfortable, so it is usually performed after you are given pain-relief medication or an anaesthetic to help numb the pain.

Extracorporeal shock wave lithotripsy can be performed to break up large kidney stones. 

Percutaneous nephrolithotomy

A percutaneous nephrolithotomy is an operation that may be used for larger kidney stones. In this procedure, an instrument called a nephroscope is inserted through a cut in the lower back to pull out the stone, or crush it into smaller pieces.

Ureteroscopy

Kidney stones that get stuck in the ureter may sometimes be removed with a procedure called ureteroscopy, or retrograde intrarenal surgery. This involves passing a flexible camera through the urethra and up into the ureter until the stone is found. A surgeon can then either remove the stone or break it up with shock waves. This procedure is generally performed under a general anaesthetic.

Open surgery

Having open surgery to remove kidney stones is not very common. It is usually reserved for very large stones. Open surgery involves making a cut in the lower back to provide access to the ureter and the kidney so that the stone can be removed.

Potential complications

In some cases, kidney stones can cause a blockage in the kidney. This can increase the chance of getting an infection and, in severe cases, cause damage to the kidney. Larger kidney stones can get stuck in part of the urinary tract and may need to be surgically removed, or broken up to allow them to pass through the tract.

Prognosis

In most cases, kidney stones are passed in the urine on their own, without medical treatment. Unfortunately, if you have experienced a kidney stone there is a high chance you may develop another one at some point in your life.

Prevention

Kidney stones can be prevented by drinking plenty of water. This reduces the high concentrations of salts and minerals in the urine that cause them to form. Simple changes to some of the foods you eat can also reduce the chance of developing some types of kidney stones. Eating a healthy diet, as well as specifically reducing your intake of salt, protein and oxalate-rich foods such as spinach, beetroot, berries and leeks, may help.

If you have had a kidney stone, finding out what type you had can be important for preventing future stones, as there are medications available that can help to prevent specific types of stones from forming. You can find out the type of kidney stone by collecting it when it passes and having your doctor send it to a laboratory for testing.

Diuretics, such as thiazides, may be prescribed to reduce the amount of calcium in your urine to prevent calcium stones. Uric acid stones may be prevented with medication such as allopurinol, which reduces the concentration of uric acid in the blood and urine. Antibiotics such as trimethroprim or amoxicillin/potassium clavulanate may be used to treat bacterial urinary tract infections that can lead to the formation of struvite stones.