Kidney stones are an often painful urologic disorder known as nephrolithiasis that sends over half a million people to emergency rooms each year in the United States alone. Millions of people develop kidney stones, including children and adults. Evidence of kidney stones, also called renal stones or renal calculi, was found in a 7,000-year-old Egyptian mummy, suggesting that kidney stones have affected humans for centuries.
A kidney stone is a small, hard crystalline deposit comprising mineral and acid salts that forms in the kidneys. Passing a kidney stone out of the body through the urinary tract is very painful, though rarely causes permanent damage. There are several kinds of kidney stones and various causes. Kidney stones may affect men and women, though some types are more common in one gender. People aged 40 and older are more likely to develop stones, though there is no minimum age limit. Even premature babies may have kidney stones.
Types of Kidney Stones
Kidney stones develop over the course of weeks or months. Minerals and acid salts make small crystals that come together to create kidney stones. Certain conditions contribute to different types of stones, whereas other stones vary by their mineral makeup.
The most common type of kidney stones are calcium stones. These stones form when calcium mixes with oxalate or other substances in the kidneys, including carbonate and phosphate. Oxalate is a substance often found in some leafy green vegetables.
People with diseases affecting the small intestine are also more likely to develop calcium stones. The group who most often gets kidney stones are 20- to 30-year-old men.
Uric Acid Stones
Uric acid is a chemical the body makes to break down substances in some foods called purines. Uric acid may form uric acid stones in people who have gout or go through chemotherapy. Men develop uric acid stones more often than women.
Struvite is a phosphate mineral that can contribute to kidney stones. Women with urinary tract infections are often found to have struvite stones. These stones may become large enough to block the bladder, ureter or kidneys. Obstructions of the urinary tract increase risk of kidney stones.
A hereditary disorder called cystinuria leads to cystine stones. Cystinuria causes the kidneys to excrete excessive amounts of some amino acids. Men and women can both get cystine stones.
Kidney stones may develop from additional substances. Certain medications contain substances that may also contribute to kidney stones. Indinavir, triamterene and acyclovir are all medications linked to stones.
Causes of Kidney Stones
Even though the basic way that stones form is known, the reason why they form is not always understood. There is no definite, single cause, but there are many known contributing factors that increase the likelihood of developing kidney stones. Generally, consuming certain foods or beverages, having particular conditions or having a family history of stones are all indicators of an elevated kidney stone risk.
Kidney Stone-Friendly Environment
The amounts of certain substances in the urine play a role in kidney stone formation by setting up an ideal environment in the kidneys. Substances like oxalate, calcium and uric acid may stick together and make stones. If there is not enough fluid in the urine to dilute these substances, the likelihood that they will come together and form stones increases. A person’s urine may also be low in substances that inhibit the combining of these crystals, which also makes it easier for the stones to form.
One substance that reduces kidney stone formation is citrate. Orange juice is particularly high in citrate. Lemonade, other citrus juices and clear diet sodas contain significant amounts of citrate as well.
Kidney Stones and Diet
Failure to drink sufficient amounts of fluids is the biggest risk factor for developing kidney stones. People who produce less than 1 liter of urine daily, which is slightly more than one quart, are more likely to form stones. Also, people who are susceptible to kidney stones may elevate their risk of stone formation by eating certain foods.
Consuming high amounts of animal proteins, sugar and salt increases risk of kidney stones. Taking too much vitamin D in supplemental form or eating too many foods that contain oxalate are known to increase risk as well. Rhubarb, spinach, beets and wheat germ are some of the foods that are naturally high in oxalate.
Another contributing dietary factor is calcium levels. Not consuming enough dietary calcium alters the balance between calcium and oxalate, leading to greater excretion of oxalate and a higher chance that oxalate stones will develop. Foods that are high in calcium include dairy products, seafood and leafy green vegetables. A doctor may recommend reducing oxalate food consumption and/or increasing calcium foods depending on a person’s existing levels of these substances
Contributing Conditions and Additional Risk Factors
People with a family history of stones or who have certain hereditary conditions have a higher risk of kidney stone formation. Over 70 percent of people who have renal tubular acidosis, which is a rare hereditary disease, get kidney stones. Other inherited diseases that increase risk of kidney stones include:
- Cystinuria (overproduction of the amino acid cystine)
- Hypercalciuria (excessive absorption of calcium)
- Hyperoxaluria (overproduction of oxalate)
Other conditions that are linked to kidney stones, include:
- Chronic bowel inflammation
- Cystic kidney disease and other kidney disorders
- Diabetes, high blood pressure and other chronic diseases
- Excessive vitamin D
- Hyperthyroidism and other metabolic disorders
- Urinary tract infections
Diuretics, also called water pills, may contribute to greater calcium in the urine. People who have recently had intestinal bypass surgery or ostomy surgery are at a higher risk of stone formation too.
Kidney stones do not always cause symptoms. Stones may pass easily through the ureter, which is a thin tube that links the kidneys and bladder. They may then leave the body through the urine. However, if a kidney stones gets stuck, then severe pain is commonly experienced.
Typical symptoms of kidney stones include:
- Abdominal pain
- Blood in the urine
- Chills or fever
- Groin pain
- Nausea or vomiting
- Testicle pain in men
Kidney stone pain is generally felt early in the morning and late at night; afternoon pain is uncommon. Pain often starts on one side of the waist and gradually increases in pain as it moves down toward the groin. The pain sometimes goes away and then returns quickly.
Blood in the urine indicates ureter or kidney irritation due to a passing kidney stone. The blood is not always visible.
Kidney Stones Diagnosis
There are several tests and exams doctors use to diagnose kidney stones. If palpating the abdomen or lower back causes pain, this indicates a possible kidney stone. However, this is not a conclusive test.
A urinalysis test that analyzes substances in the urine helps identify the type of kidney stone. A urinalysis reveals the level of uric acid, oxylate and calcium in the urine as well as the presence of crystals, red blood cells or an infection.
Diagnostic machines show the location of kidney stones and any blockages or obstructions in the urinary tract. Types of tests commonly used include:
- Abdominal CT scan
- Abdominal MRI
- Abdominal X-ray
- Intravenous pyelogram
- Kidney MRI
- Kidney ultrasound
- Retrograde pyelogram
The most common type of test administered is an abdominal CT (computerized tomography) scan. This test reveals the location of stones, their size and whether the affected kidney or the ureter is inflamed. Usually, doctors do not use a contrast dye when scanning for kidney stones, which limits the detail of the scan’s images.
Sometimes, a CT scan is contraindicated, such as when the patient is a pregnant woman. An ultrasound is a safe alternative method for detecting kidney stones and obstructions. Ultrasounds require an ultrasound technician to operate and interpret the images. These technicians are not always available.
When a patient is known to have a kidney stone, a doctor may use an abdominal X-ray to follow the stone’s movement toward the bladder. Routine X-rays sometimes initially reveal the presence of a stone.
Kidney Stones Treatment
The body typically excretes kidney stones on its own. However, some people need medications to handle the pain or to break down certain types of stones. Surgery is required to remove the stones if they cannot pass stones safely by themselves. Lifestyle changes can also help treat kidney stones. http://www.youtube.com/watch?v=IEFYeB0Jf-s”
Doctors may suggest over-the-counter and prescription pain killers for people with painful kidney stones. Ibuprofen (Advil, Motrin), naproxen sodium (Aleve) and acetaminophen (Tylenol) are all mild pain relievers people can get without a prescription.
The pain may be great enough to require stronger medications and even hospitalization. While in the hospital, it is common to give people fluids intravenously to dilute their urine. Prescription medications can assist by breaking down kidney stones and getting rid of material that causes stones. These medications may include:
- Diuretics, including thiazide diuretics
- Phosphate solutions
- Sodium bicarbonate or sodium citrate
A type of medication called alpha blocker relaxes ureter muscles and can assist in passing kidney stones. Allopurinol may also be prescribed specifically for uric acid stones. Antibiotics may be used for treating struvite stones.
Some people require surgery for kidney stones. Reasons for surgery include:
- A stone is too big to pass unaided
- A stone is growing in size
- A stone is blocking the flow of urine, causing kidney damage or an infection
- Uncontrollable pain
There are several types of surgical procedures used to break up or take out stones. Most procedures aim to break up stones so they can pass on their own. Which treatment is recommended depends on the size and location of the stone.
Extracorporeal Shock Wave Lithotripsy
Extracorporeal shock-wave lithotripsy (SWL) is a type of procedure used on stones smaller than 1/2 an inch and that are found near the ureter or kidney. SWL uses sound or shock waves to break up the kidney stones so they are able to leave the body through the urine. The procedure is only 45 to 60 minutes long. Light anesthesia or sedation is necessary because SWL is painful.
Side effects from the procedure include contusions on the abdomen or back, bloody urine, and bleeding around the kidney and nearby organs. The patient may experience discomfort as the remaining pieces of the stones pass through the body.
If SWL fails or if the kidney stones are too large for it to work, doctors may recommend percutaneous nephrolithotomy. This is a surgical procedure for the removal of stones both in and near the kidney. It may also be used in people whose kidneys and surrounding areas and not formed correctly.
During percutaneous nephrolithotomy, a surgeon makes a small surgical cut in the back and inserts a tube called an endoscope. The kidney stone is then removed through the tube. Anesthesia during the operation and one to two days of hospitalization are to be expected for this procedure.
Ureteroscopy is a procedure used on kidney stones found in the lower urinary tract. A thin tube called a ureteroscope is inserted through the urethra and bladder to the ureter. The tube is lighted and has a small camera. The purpose of the ureteroscope is to get a clear picture of the kidney stone. The surgeon may then use tools to break up the stone or grab it for removal. A local or general anesthesia is typically used during a ureteroscopy.
In rare cases, an open surgical procedure called nephrolithotomy may be used to take out the stones. Surgeons only select this option when all other procedures have failed or will not work.
Parathyroid Gland Surgery
People who have calcium stones may need parathyroid gland surgery. The parathyroids are small glands located in the throat that make important hormones. Some people have a condition called hyperparathyroidism, which is when the parathyroid glands are overactive and make excessive amounts of hormones.
Hyperparathyroidism can result in too much calcium and kidney stones. Benign tumors in parathyroid glands may cause hyperparathyroidism. When tumors are present, surgery to remove the tumorous growths can inhibit kidney stone development.
Making some lifestyle changes can help treat kidney stones. Drinking a minimum of 6 to 8 glasses of water daily results in a enough urine to counter kidney stone development and help pass existing stones in most cases. A good method to tell if someone is drinking enough water is to observe if the urine is almost or completely clear. However, people with cystine stones may need to drink over a gallon of water daily to dilute the cystine concentration in the urine.
Although eating more calcium may be beneficial for kidney stones, taking calcium supplements can increase the risk. People with kidney stones or who are high risk should avoid calcium pills, including antacids with a calcium base.
Doctors may also recommend avoiding foods fortified with vitamin D. People with highly acidic urine can also benefit from eating less meat, including poultry and fish.
Kidney stones can result in several moderate to severe complications, such as:
- Kidney damage
- Kidney stone recurrence
- Reduced kidney function
- Ureter obstruction
- Urinary tract infections
Kidney Stones Prevention
Preventative measures can go a long way to reducing the likelihood that someone will get kidney stones. For people who have been diagnosed with kidney stones, the first step for prevention is to catch the stones when they pass. Doctors can then analyze the stones and determine their type. What kind of stone a person has gives a clue as to how it formed and suggests ways to prevent future occurrences, such as dietary modifications to lower oxalate consumption. Doctors may make other specific recommendations based on individuals medical history and the results of their stone analysis, but drinking more water is almost always helpful.
Medications may be prescribed and kept at home for people who have passed stones and know what the symptoms of another stone feel like. These medications may break down future stones so people can pass them without additional treatment.
Drinking more orange and grapefruit juice due to the high citrate content may help prevent stones as well.
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