Kidney stone

A kidney stone (medical term: renal calculus or nephrolith) is a deposit formed in the kidneys from minerals in the urine. Stones typically pass naturally out of the body through the bladder. Stones that do not pass can cause blockage or irritation and result in blood in the urine; pain in the groin, back, or abdomen; infection; stomach aches; nausea; fever; and foul-smelling urine. Made of a composite of minerals, the most common kidney stones are calcium oxalate, cystine, struvite, and uric acid. Risk factors for developing a kidney stone include dehydration, diet, family history, and certain medical conditions. Kidney stones are diagnosed via an ultrasound, CT scan, or intravenous pyelography (IVP). They can be treated with medications, with procedures to help break up stones, or with surgery to remove stones.

Background

The kidneys are bean-shaped organs located on either side of the spine near the lower rib cage. Connected to the bladder via tubes called the ureters, their primary function is to remove waste products and extra fluid from the body via the urinary tract. In addition to balancing the body’s fluids, the kidneys are essential in producing certain hormones and in regulating the body’s acid, salt, and potassium levels.

Kidney stones develop from excess mineral wastes in the urine that form into crystals. The crystals then attach to other elements to form a solid that in most cases passes out of the body naturally. If there is insufficient liquid to wash them out, a stone the size of a small pebble or as large as a golf ball can form and get stuck in the kidney or ureter.

The four primary types of kidney stones are:

Calcium oxalate: These are the most common type of kidney stones and are created when calcium combines with the waste product oxalate in the urine.

Cystine: Caused by an inherited disorder called cystinuria, where an excess of the natural substance cystine leaks into the urine and forms a kidney stone that gets stuck in the kidney, ureters, or bladder. The condition can be controlled but not cured, putting those affected at risk for recurring stones. According to Genetics Home Reference in 2014, an estimated one in ten thousand people have cystinuria, including children.

Uric acid: Thought to be caused by a high purine diet or obesity, these kidney stones are comprised of monosodium urate crystals.

Struvite: Stones that result from an infection in the urinary tract.

The peak age for developing kidney stones is twenty to fifty years; however, the condition can also affect children and the elderly. Only a small percent of cases result from family history, and men are more likely to have stones than women. There is no single known cause for developing kidney stones; however, possibilities and risk factors include: dehydration, diabetes, obesity, weight loss surgery, kidney cysts, osteoporosis, chronic diarrhea, inflammatory bowel disease, excess consumption of fructose, a high-salt diet, high intake of animal protein, low level of calcium, infections, and high blood pressure. In addition, having one kidney stone increases the risk of having another stone, as well as the risk of acquiring chronic kidney disease.

Overview

Some kidney stones, called "silent stones," do not produce symptoms; rather they are experienced as sudden onset of excruciating pain in the lower back, groin, side, or abdomen. The pain is so intense that it has been described as broken bones or worse than childbirth. Additional symptoms of a kidney stone include: nausea, vomiting, urinary urgency, difficulty urinating, testicular or penile pain, bloody urine, fever, and chills.

Kidney stone diagnosis begins with a physical examination and medical history and blood and urine tests to evaluate the health of the kidneys. These are followed by imaging tests that allow doctors to examine a stone’s shape, size, and location. The tests include high-resolution computed tomography (CT) scan of the kidneys to the bladder; intravenous pyelogram (lVP), an X-ray of the urinary system taken after injecting a dye; and KUB X-ray (kidney-ureter-bladder) showing the size and position of the stone (helping doctors determine if the size warrants a shock wave treatment to break up the stone).

To assist a kidney stone in passing without surgical intervention, patients are asked to drink a lot of water or take a prescribed medication to help make the urine less acidic. Among the factors that influence a stone’s ability to pass naturally are the person’s size, the stone’s size, previous stone passage, pregnancy, and prostate enlargement.

Another alternative is a noninvasive procedure called shock wave lithotripsy (SWL), which uses high-energy sound waves to break a large stone into smaller fragments so that it can pass naturally out of the body through the urine.

If these treatments are not effective, some surgical techniques to remove a kidney stone include ureteroscopy, where a tool called an endoscope is inserted via the ureter to retrieve or get rid of the stone. Another procedure, percutaneous nephrolithotomy/nephrolithotripsy, is minimally invasive and is used in cases of large or irregularly shaped kidney stones, infection, or stones that SWL does not break up. Entering the kidney through a small incision in a person’s back, a miniature fiber optic camera called a nephroscope and other miniscule instruments are threaded through and used to remove the stone (nephrolithotomy) or to break up and then remove the stone (nephrolithotripsy). The procedure, which can last twenty to forty-five minutes, depending on the position of the stone, is carried out under general anesthesia and requires a two- to three-day hospitalization. This is the most effective technique for ensuring a person is stone-free.

Prevention is always preferable, and some doctor-recommended steps to help prevent kidney stones from developing or recurring include drinking plenty of fluids, preferably water; drinking lemon juice or lemonade; decreasing soda and coffee/tea consumption; decreasing consumption of high-oxalate foods, such as peanuts, wheat germ, spinach, and rhubarb (for people who have experienced calcium oxalate kidney stones); limiting salt and high-fructose corn syrup consumption; eating plenty of fruits and vegetables, which make the urine less acidic; and maintaining a healthy weight by eating a balanced diet.

Although people with a history of kidney stones remain at risk for future stones, the prognosis for treatment is very good.

Bibliography

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