Kidney Stones

Overview

Kidney stones (also known as renal calculi, nephrolithiasis, or urolithiasis) are hard irregularly shaped solid mass or crystals made of minerals and salts that form inside your kidneys. These stones can be as small as a grain of sand or as large as a golf ball.

Kidney stones can affect any part of your urinary tract — from your kidneys to your bladder. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together.

Passing kidney stones can be quite painful, but the stones usually cause no permanent damage if they’re recognized in a timely manner. Depending on your situation, you may need nothing more than to take pain medication and drink lots of water to pass a kidney stone. In other instances – for example, large stones get trapped in the urinary tract, are associated with a urinary infection or cause complications – surgery may be needed.

Your doctor may recommend preventive treatment to reduce your risk of recurring kidney stones if you’re at increased risk of developing them again.

Symptoms

A kidney stone usually does not show any symptoms until it moves around within your kidney or passes into your ureters – the tubes connecting the kidneys and the bladder. If it becomes lodged in the ureters, it may block the flow of urine and cause the kidney to swell and the ureter to spasm, which can be very painful. At that point, you may experience these signs and symptoms:

Severe, sharp pain in the side and back, below the ribs
Pain that radiates to the lower abdomen and groin
Pain that comes in waves and fluctuates in intensity
Pain or burning sensation while urinating

Other signs and symptoms may include:

Pink, red, or brown urine
Cloudy or foul-smelling urine
A persistent need to urinate, urinating more often than usual or urinating in small amounts
Nausea and vomiting
Fever and chills if an infection is present

Pain caused by a kidney stone may change – for instance, shifting to a different location or increasing in intensity – as the stone moves through your urinary tract.

Causes & Stone types

Kidney stones usually have no definite, single cause, though several factors may increase your risk. Kidney stones form when your urine contains more crystal-forming substances such as calcium, oxalate, and uric acid – than the fluid in your urine can dilute. At the same time, your urine may lack substances that prevent crystals from sticking together, creating an ideal environment for kidney stones to form. The stone-forming substances are:

Calcium
Oxalate
Uric acid
Phosphate
Cystine (rare)
Xanthine (rare)

The above mentioned substances are also types of commonly found kidney stones.

Risk Factors

White men in their 30s and 40s are most likely to get kidney stones. However, anyone can develop kidney stones. Factors that increase your risk of developing kidney stones include:

Family or personal history. If someone in your family has had kidney stones, you’re more likely to develop stones, too. If you have already had one or more kidney stones, you’re at increased risk of developing another.
Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm, dry climates and those who sweat a lot may be at higher risk than others.
Certain diets. Eating a diet that’s high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.
Obesity. High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones.
Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the amounts of stone-forming substances in your urine.
Other medical conditions such as renal tubular acidosis, cystinuria, hyperparathyroidism and repeated urinary tract infections also can increase your risk of kidney stones.
Certain supplements and medications, such as vitamin C, dietary supplements, laxatives (when used excessively), calcium-based antacids, and certain medications used to treat migraines or depression, can increase your risk of kidney stones.

Complications

Apart from causing symptoms such as pain, vomiting and blood in the urine, kidney stones can cause serious medical complications. These include:

Severe infections including septicemia (blood poisoning) which can be life-threatening.
Renal scarring and damage to the kidneys, resulting in permanent renal failure.
Loss of function of a kidney resulting in the need for removal of the kidney (nephrectomy).
Bladder blockage can result when a large kidney stone has managed to pass into the bladder but gets stuck in the urethra resulting in painful urinary retention.

Diagnosis and Tests

If your doctor suspects that you have a kidney stone, you may have diagnostic tests and procedures, such as:

Blood testing. Blood tests may reveal too much calcium or uric acid in your blood. Blood test results help monitor the health of your kidneys and may lead your doctor to check for other medical conditions.
Urine testing. The 24-hour urine collection test may show that you’re excreting too many stone-forming minerals or too few stone-preventing substances. For this test, your doctor may request that you perform two urine collections over two consecutive days.
Imaging. Imaging tests may show kidney stones in your urinary tract. High-speed or dual energy computerized tomography (CT) may reveal even tiny stones. Simple abdominal X-rays are used less frequently because this kind of imaging test can miss small kidney stones. Ultrasound, a noninvasive test that is quick and easy to perform, is another imaging option to diagnose kidney stones.
Analysis of passed stones. You may be asked to urinate through a strainer to catch stones that you pass. Lab analysis will reveal the makeup of your kidney stones. Your doctor uses this information to determine what’s causing your kidney stones and to form a plan to prevent more kidney stones.

Treatment and Medication

Once diagnosed, your healthcare provider will first determine if you even need treatment. Some smaller kidney stones may leave your system when you urinate. This can be very painful. If your provider decides that you do need treatment, your options include medications and surgery.

Medications. Medications may be prescribed to:

Decrease pain. Your healthcare provider may recommend that you take an over-the-counter medication like ibuprofen or, if you’re in the emergency room, an IV narcotic.
Manage nausea/vomiting.
Relax your ureter so that the stones pass. Commonly prescribed medicines include tamsulosin (Flomax®) and nifedipine (Adamant® or Procardia®).

You should ask your healthcare provider before you take ibuprofen. This drug can increase the risk of kidney failure if taken while you’re having an acute attack of kidney stones — especially in those who have a history of kidney disease and associated illnesses such as diabetes, hypertension and obesity.

Surgery. There are four types of surgeries used to treat kidney stones. The first three are minimally invasive, meaning that the surgeon enters your body through a natural opening (like your urethra), or makes a small incision.

Ureteroscopy: To perform this procedure, a small instrument called an ureteroscope is inserted in your urethra, through your bladder and into a ureter. This instrument shows the kidney stones and then retrieves them in a surgical “basket,” or breaks them apart using a laser. These smaller pieces of the kidney stones are then easily able to exit your body through your urinary tract.
Shockwave lithotripsy: In this procedure, you’re placed on a special type of surgical table or tub. High-energy shockwaves are sent through water to the stone(s). The shockwaves break apart the stones, which are then more easily able to exit your body.
Percutaneous nephrolithotomy: When kidney stones can’t be treated by the other procedures — either because there are too many stones, the stones are too large or heavy or because of their location — percutaneous nephrolithotomy is considered. In this procedure, a tube is inserted directly into your kidney through a small incision in your back. Stones are then disintegrated by an ultrasound probe and suctioned out so that you don’t have to pass any fragments. A urethral stent is placed after the procedure (an internal tube from the kidney to the bladder which is removed one week later). Patients are typically kept overnight for observation.
Open stone surgery: A longer cut is used during this surgery. Compared to minimally invasive procedures, it’s rarely performed (0.3% to 0.7% of cases)

Prevention

There are several ways to decrease your risk of kidney stones, including:

Drink water throughout the day. For people with a history of kidney stones, doctors usually recommend drinking enough fluids to pass about 2.1 quarts (2 liters) of urine a day. Your doctor may ask that you measure your urine output to make sure that you’re drinking enough water.
If you live in a hot, dry climate or you exercise frequently, you may need to drink even more water to produce enough urine. If your urine is light and clear, you’re likely drinking enough water.
Eat fewer oxalate-rich foods. If you tend to form calcium oxalate stones, your doctor may recommend restricting foods rich in oxalates. These include rhubarb, beets, okra, spinach, Swiss chard, sweet potatoes, nuts, tea, chocolate, black pepper and soy products.
Choose a diet low in salt and animal protein. Reduce the amount of salt you eat and choose nonanimal protein sources, such as legumes. Consider using a salt substitute, such as Mrs. Dash.
Continue eating calcium-rich foods, but use caution with calcium supplements. Calcium in food doesn’t have an effect on your risk of kidney stones. Continue eating calcium-rich foods unless your doctor advises otherwise.
Ask your doctor before taking calcium supplements, as these have been linked to increased risk of kidney stones. You may reduce the risk by taking supplements with meals. Diets low in calcium can increase kidney stone formation in some people.
Ask your doctor for a referral to a dietitian who can help you develop an eating plan that reduces your risk of kidney stones.

Prognosis

The outlook for kidney stones is very positive, although there is a risk of recurrence (the stones coming back). Many kidney stones pass on their own over time without needing treatment. Medications and surgical treatments to remove larger kidney stones are generally very successful and involve little recovery time.

It’s possible to get kidney stones multiple times throughout your life. If you keep developing kidney stones, your healthcare provider may work with you to discover why the stones happen. Once the cause is found, you may be able to make dietary changes to prevent future stones.