Kidney Stones

Introduction to the Urinary Tract

The urinary tract or system consists of the kidneys, ureters, bladder, and prostate in males and urethra. The kidneys remove extra water and wastes from the blood, converting it to urine. They keep a stable balance of salts and other substances in the blood as well as produce hormones that help build strong bones and help form red blood cells. Narrow tubes called the ureters carry urine from the kidneys to the bladder which is a chamber in the lower abdomen.

What is a kidney stone?

A kidney stone is a hard mass formed by crystals in the body. Normally urine has natural chemicals to stop crystals forming. When urine is concentrated the chemicals stop working and stones form.

When stones become too large to pass through the urinary system easily they can become stuck in the kidneys or urinary tract and cause significant pain.

Kidney stones vary in size, color, shape and chemical make up.

Who gets kidney stones?

Kidney stones are very common with 1 in 10 men and 1 in 20 women experiencing a stone in their lifetime. Stones can occur at any age but on average around 20-40 years. Once a person has had one stone, he or she is more prone to developing others. This is a 50% chance over 5 years.

A person with a family history of kidney stones is more likely to develop stones. Urinary tract infections, kidney disorders such as cystic kidney diseases, and metabolic disorders such as hyperparathyroidism are also linked to stone formation.

Kidney Stone descriptions

  • Uroliathis describe stones occurring in the urinary tract. The most common type contains calcium in combination with either oxalate or phosphate. Stones composed of uric acid are less common.
  • Ureteric stone describes the movement of a stone down the ureter
  • Renal calculi describes stones in the kidney or ureter
  • Nephraliasis is another name used to describe formation of calcium in the kidneys
  • Struvite stone is an uncommon type of stone caused by infection in the urinary tract.
  • Cystine stones are caused by a rare genetic disorder called “cystinuria.”

Gallstones and kidney stones are not related. They form in different areas of the body and have different causes. If you have a gallstone, you are not more likely to develop kidney stones.

Kidney Stone descriptions

What causes kidney stones?

Doctors do not always know what causes a stone to form. While certain foods may promote stone formation in people who are susceptible, foodstuffs only contribute a small amount to the likelihood of forming stones.

More than 70% of people with a rare hereditary disease called renal tubular acidosis develop kidney stones. Cystinuria and hyperoxaluria are two other rare, inherited metabolic disorders that often cause kidney stones. In cystinuria, too much of the amino acid cystine, which does not dissolve in urine, is voided. This can lead to the formation of stones made of cystine. In patients with hyperoxaluria, the body produces too much of the salt oxalate. When there is more oxalate than can be dissolved in the urine, the crystals settle out and form stones. A high concentration of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or urinary tract. Other causes of kidney stones are hyperuricosuria (a disorder of uric acid metabolism), excess intake of vitamin D and blockage of the urinary tract. A high concentration of calcium may also lead to the patient developing gout. Calcium oxalate stones may also form in people who have a chronic inflammation of the bowel or who have had an intestinal bypass operation, or ostomy surgery.

As mentioned above, struvite stones can form in people who have had a urinary tract infection. People who take the protease inhibitor Indinavir, a drug used to treat HIV infection and AIDS, are at risk of developing kidney stones although this is extremely rare.

What are the symptoms?

Usually, the first symptom of a kidney stone is extreme pain. The pain often begins suddenly when a stone moves in the urinary tract, causing irritation and blockage. Typically, a person feels a sharp, cramping pain in the back and side area of the kidney, or in the lower abdomen. Sometimes nausea and vomiting occur. Later, pain may spread to groin. If the stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder.

As a stone grows or moves, blood may appear in the urine. As the stone moves down the ureter closer to the bladder, you may feel the need to urinate more often or feel a burning sensation during urination. If fever or chills accompany any of these symptoms, an infection may be present. In this case, you should contact a doctor immediately.

How are kidney stones diagnosed?

Sometimes a ‘silent’ stones –those that do not cause symptoms – are found on X-Rays or Ultrasound taken during a general health exam. Some stones may be present with blood in the urine, and or with no pain. Recurrent urinary tract infections not responding to antibiotic treatment may also be a sign of stones.

More often, kidney stones are found on CT scan taken in an emergency department on someone who complains of blood in the urine or sudden pain. These diagnostic images give the doctor valuable information about the stone’s size and location.

Blood and urine tests help detect any abnormal substance that might promote stone formation. The doctor may also decide to scan the urinary system using a special x-ray test called IVP (intravenous pyelogram). A plain abdominal X-Ray and ultrasound pick up most stones but are not as accurate as a CT scan. The best test for you will be decided by your doctor.

How are kidney stones treated?

Fortunately, surgery is not always necessary. Many kidney stones can pass through the urinary system with plenty of water (2 to 3 litres a day) to help move the stone along. The likelihood of passing a stone is dependent on the size and position of the stone. The smaller and lower the urinary tract the more likely to pass. If pain is severe you will be admitted to the hospital and given strong painkillers.

Often, you can go home during the process, drinking fluids and taking pain medication as needed. Recently we have begun to use a new drug called flomaxtra, which relaxes the muscle of the ureter and helps stones pass. The doctor usually asks you to save the past stone(s) for testing. You can catch it in a cup of tea strainer used only for this purpose.

What tests are done?

In every person who has had a stone, we check the level of calcium in the blood and also perform a urine culture. If a stone has been removed, or if you’ve passed a stone and saved it, the laboratory can analyse it to determine its composition.

If you’ve had a number of kidney stones we usually carry out a more detailed series of tests to try to find other treatable causes. You may be asked to collect you urine for 24 hours after a stone has passed or been removed. The sample is used to measure urine volume and levels of acidity calcium, sodium, uric acid, oxalate, citrate, and creatinine (a product of muscle metabolism). More 24 hour urine collections are sometimes needed to determine whether the prescribed treatment is working.

Lifestyle changes

By far the most important lifestyle change to prevent stones is to drink more fluids….water is best. If you tend to form stones, you should try to drink enough liquids throughout the day to produce at least two litres of urine every 24 hour period. As stones form only when the urine is concentrated, it is possible to know when you are at high risk – look at your urine – if it is dark then you should be drinking more. Aim for pale clear urine.

People who form calcium stones used to be told to avoid dairy products and other foods with high calcium content. But recent studies have shown that foods high in calcium don’t increase the risk of developing stones.

Medical Therapy

As well as lifestyle changes mentioned above, drugs such as hydrochlorothiazide are also occasionally used to help prevent calcium stones. These drugs decrease the amount of calcium released by the kidneys into the urine. Uric acid stones are the only stones that can be dissolved. This is difficult but is possible by taking medicine to make the urine less acidic (the pH must be over 6.5) and taking a large amount of fluids. Once they are dissolved, fluids alone can prevent more stones.

To prevent cystine stones, it is necessary to drink enough water each day to dilute the concentration of cystine that escapes into the urine, which may be difficult. More than four litres of water may be needed every 24 hours, and a third of that must be drunk during the night. Various medicines are used at times also.

For struvite stone(s) that have been totally removed, the first line of prevention is to keep the urine free of the bacteria that can caused infection. Your urine will be tested regularly to be sure that no bacteria are present. People with hyperparathyroidism sometimes develop calcium stones. Treatment in these cases is usually surgery to remove the parathyroid glands (located in the neck). In most cases, only one of the glands is enlarged. Removing the glands cures the patient’s problem with hyperparathyroidism and with kidney stones as well.

Surgical treatment

Surgery is reserved as an option for cases where other approaches have failed or shouldn’t be tried. A Surgical procedure may be needed to remove a stone if:

  • Does not pass after a reasonable period of time and causes constant pain.
  • Is too large to pass on its own, or is caught in a difficult place.
  • Blocks the flow of urine.
  • Causes ongoing urinary tract infection.
  • Damages kidney tissue or causes constant bleeding
  • Has grown larger (as seen on follow-up x-ray studies).

Until the last few decades, surgery to remove stones meant an open operation. It involved cutting the skin and was very painful. It also required a lengthy recovery time (4-6 weeks). Today, surgical treatment for stones is greatly improved and open surgery is very rarely required. Most treatment options are much easier for the patient and do not require major surgery.

Your surgeon will discuss with you which option is best for you.

Prevention points

  • If you have a family history of stones or have had more than one stone, you are likely to develop more stones. Drink plenty of fluids – water is best.
  • If you are at risk for developing stones, ask your doctor to perform certain blood and urine tests to determine which factors can best be altered to reduce that risk. You may need medicines to prevent stones from forming.
  • If you have chronic urinary tract infections and stones you will often need the stone removed if you doctor determines that the infection results from the stone’s presence.
  • Ensure you receive careful follow up to be sure that the infection has cleared.
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