Kidney stone

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at March 22, 2016
StartDiseasesKidney stone

Kidney stones are hard mineral deposits that form within the kidneys. They are also referred to as a nephrolith or renal calculus.


Definition & Facts

Kidney stones are hard, solid materials that have formed within the kidneys from minerals commonly found in urine. When there is an overabundance of these materials within urine, crystals form that attract other minerals, causing the stone to form. The minerals that most commonly lead to kidney stones are salts, calcium, phosphates, oxalate, cystine and xanthine.

Kidney stones may remain small and stay within the kidney or pass out of it into the ureters. Small stones can be passed out of the body during urination without symptom. Larger ones may require focused treatment or surgical removal.

Symptoms & Complaints

Small kidney stones may move from the kidneys through the urinary tract without symptoms. Larger stones will produce more pronounced symptoms. Pain is the most common symptom of kidney stones.

Pain from kidney stones begin when they cause irritation or blockage in the ureters. This pain will be focused around the lower back on either the left or right side of the spine or as a stomach ache that will not go away. It may also extend into the groin and may come in waves.

Pain from kidney stones changes in intensity or location as the stone moves through the urinary tract. Other symptoms associated with kidney stones include:

In some cases a kidney stone may be accompanied by an infection such as a urinary tract infection that has similar symptoms.


There is no one specific factor that leads to the formation of kidney stones. There may not be enough fluid content of the urine to dilute the minerals responsible and pass them from the body. This causes them to crystalize and bind together. Doctors usually analyze kidney stones once they have been passed to determine their composition as this gives a clue as to what may have caused the stone to form and an appropriate course of action to prevent future stones.

There are four main types of kidney stones: calcium, struvite, uric acid, and cystine. While each kind may produce the same symptoms they all have a different formation and point to a different possible cause. Calcium stones are the most common kind of kidney stone and are formed from an excess of calcium oxalate or calcium phosphate.

Struvite stones form quickly and may result from a urinary tract infection. Uric acid stones point to reduced fluid intake. Cystine stones are usually from a hereditary condition that causes the kidneys to excrete too much of the amino acids called cystinuria.

Diagnosis & Tests

If a doctor suspects a kidney stone is the cause of any of the above symptoms the first tests performed will be imaging to get a correct diagnosis. This also lets the doctor know exactly where the stone is located.

The preferred test for locating and diagnosing kidney stones is a CT scan. A CT scan is often used for a quick and exact diagnosis of kidney stone especially if a patient is at an emergency department. X-rays may also be used to locate a kidney stone but unlike a CT scan they can miss smaller stones. An X-ray is good to determine if the stone can be treated with shock wave treatment.

Blood tests and urine testing may also be performed to monitor the health of the kidneys. Blood tests can highlight excess calcium or uric acid. Urine tests measure the amount of stone-forming minerals or the lack of stone-preventing substances. Both are important for preventing future kidney stones.

After a stone is passed doctors may analyze the contents of it to correctly understand what substances formed it in the first place. Like the blood and urine tests this helps prevent future stones.

Treatment & Therapy

Depending on the size and location of the stone several different treatment options may be utilized. If a stone is small then the most favored approach is to let it pass through the urinary tract on its own. This could take several weeks. In order to help the stone pass patients will need to drink more water and may be given medication to help with pain while they are waiting to pass the stone.

Tamsulosin is most often prescribed to help with kidney stones by relaxing the ureter and allowing the stone to easily pass. One non-invasive method of treating kidney stones is with extracorporeal shock wave lithotripsy. X-rays and ultrasounds are first used to locate the stone. Then sound waves are forced onto the stones to break them into smaller pieces. Pieces of stones are collected through a strainer as they pass.

If a stone is too big to remove in any of these ways surgical removal may be necessary. One option is with a nephrolithotomy where a stone is removed through an incision in the back. Another method uses a ureteroscope inserted through the urethra and bladder to extract or break up stones.

Prevention & Prophylaxis

One of the most important ways to prevent future kidney stones is to drink plenty of water each day. In order to ensure that a patient is drinking enough fluids they may be asked to measure their urine output. Depending on the composition of previously passed stones some dietary changes may be required.

Medications may also be prescribed to help reduce the chances of kidney stones forming. Consulting a dietitian may also be recommended as this can help patients steer clear of stone-causing foods and substances, such as over-the-counter calcium supplements that may increase the risk of kidney stones.