What Are Kidney Stones?
Kidney stones, also known as renal lithiasis, is a condition whereby abnormal accumulations of solid matter are formed in the urinary system. They become a problem when they interfere with the flow of urine within or out of the kidney. Kidney stones can cause severe pain when they attempt to move through the ureters, small tubes that connect the kidney and the bladder.
Kidney stones have been recognized since the days of the pyramids in ancient Egypt. In recent decades, their incidence has been increasing. This is usually attributed to diet and a lack of fluids, especially water. Currently, approximately 10% of the population will experience a kidney stone in his or her lifetime. Certain folks have a higher risk of developing kidney stones. Most cases are found in people between the ages of 20-70, and they are more common in men than in women. Race also plays a factor. Caucasian Americans are more likely to have kidney stones than African-Americans. If you have a close relative who has a history of kidney stones, there is a slightly higher chance of you developing them. Also, if you have had one bout with kidney stones, you are more likely to have them again.
There are also some rare, inherited diseases that can cause increased risk. Two of the major ones are:
- Renal Tubular Acidosis: This condition happens when the nephrons do not filter the blood properly, and the body is left in an abnormally acidic state.
- Cystinuria: This is due to excessive excretion of certain amino acids in the urine.
How Are Kidney Stones Formed?
The kidneys are two bean-shaped organs about the size of your fist that are located behind the abdomen on either side of the spine. One of their jobs is to produce urine. Blood flows through a network of special tubes in the kidneys called nephrons. There may be up to a million nephrons in your kidneys. The nephrons function as a filter for the blood, and they determine the amount of fluid and dissolved substances that flow out of the kidneys as urine. A problem develops when the dissolved substances start to solidify again. This process may begin with the formation of tiny crystals, and eventually they may clump together to form a larger object called a kidney stone.
Many kidney stones are not problematic. They are small enough to pass undetected, and they do not block the flow of urine. These are referred to as “silent stones.” Kidney stones cause trouble when they interfere with normal urine flow. When a stone attempts to move through the ureter, it can cause a blockage of urine that may lead to swelling of the kidney (hydronephrosis) or swelling of the ureter (hydroureter). Hydronephrosis can cause damage to the fragile tissues of the kidney. Hydroureter is very common with kidney stones, and causes the characteristic intense pain associated with the condition. The ureters are made up of muscle, and when there is a blockage the muscles react with painful spasms. I have never personally experienced it, but they tell me that the pain is excruciating.Many patients are given morphine and other narcotic painkillers during an attack.
There are four major types of kidney stones, all composed of different substances:
- Calcium stones: These are the most common, compromising about 80% of all kidney stones. These stones are formed because of abnormally high levels of calcium in the blood. Sometimes calcium bonds with phosphate or oxalate to form these stones. A diet high in animal proteins found in meat, poultry, and fish can be a factor. Certain diseases may also lead to elevated calcium levels and therefore calcium stones, such as: parathyroidism (enlargement of the thyroid gland or glands), hyperthyroidism (an over-active thyroid gland), renal tubular acidosis (see above), and some types of cancer.
- Struvite stones: 10% of kidney stones are of this type. They are composed of magnesium ammonium phosphate. The most common source for this compound is a substance called urease, which is a byproduct of certain types of bacteria. Urease makes the urine more alkaline, which stimulates struvite to settle out and form stones. This type of kidney stone is often found in patients who have had repeated urinary tract infections. Struvite stones often form in the nephrons. They are known to form very large stones called “staghorn stones,” and can be particularly dangerous as they can fill up and block off the nephrons.
- Uric acid stones: These are found in about 5% of all kidney stone cases. These form when uric acid levels in the blood are abnormally high. Small crystals of uric acid eventually come together to form stones. This happens inside the kidney, and throughout other parts of the body. Uric acid stones can also form large “staghorns.” Deposits in the big toe are common, and this symptom is also associated with a condition called gout, an arthritis-like disease causing pain and inflammation in the joints due to uric acid deposits.
- Cystine stones: Only 2% of stones are cystine. These are caused by the improper processing of amino acids in the body (see cystinuria above).
What Are the Symptoms of Kidney Stones?
The most common symptom of a kidney stone is intermittent bouts of severe pain that fluctuate in intensity in 5-15 minute cycles. The pain is sometimes described as “crampy” and “spasmodic,” and health care providers call it “colic.” It is due to a kidney stone in the ureter. The pain often begins on the flank, between the lower ribs and the hip. Then it tends to radiate along the inner thigh as the stone moves closer to the kidney. Females often feel pain in the vulva, and males in the testicles.
Other common symptoms are blood in the urine, butty or foul-smelling urine, painful and frequent urination, nausea, and vomiting. Fever and chills can indicate a kidney infection (pyelonephritis) from bacteria being trapped in the kidney due to a blocked ureter.
While actively passing a kidney stone, it is important that the patient’s urine be strained through a sieve to capture the stone. The stone can then be analyzed to determine its type. This can also help in identifying what has caused the kidney stones to form. In addition, urine is often collected for 24 hours after the stone has passed.
How is a Diagnosis of Kidney Stones Made?
The distinctive location and intensity of the pain, along with other telltale symptoms and any past history of kidney stones, are often the best diagnostic tools. There are also tests available that can help your health care provider determine if you have a kidney stone:
- A common x-ray of the kidneys, ureters, and bladder may or may not show kidney stones if they are present.
- An Intravenous Pyelogram (IVP) or excretory urogram is a series of x-rays made after an iodine solution is injected into a vein. This can make stones and obstructions easier to spot. Personally, I would be careful about injecting such a foreign substance into my body.
- The latest technology is called a Spiral CT Scan. No dye is used, but even some mainstream physicians express concerns about excessive radiation exposure during this imaging test. The test is also very expensive if you have to cover it out of pocket.
How Can I Prevent Kidney Stones?
The best way to prevent getting a kidney stone is to drink lots of pure, clean water, especially if you have had kidney stones in the past. Experts recommend that you pass about 2.5 quarts of urine per day, which necessitates drinking about 3.5 quarts of fluids (water is best) per day (more in hot dry weather). Getting regular exercise is also beneficial as well. Studies have shown that a sedentary lifestyle tends to encourage the bones to release more calcium than an active lifestyle will. Diet is important too. Generally it is recommended to consume foods that are low in animal protein, low in sodium, and high in fiber. Some specific foods to avoid are: organ meats, herring, anchovies, chocolate, tea, berries, black pepper, and beer. These tend to encourage the formation of stones.
One interesting study seems contradictory at first glance. You would think a diet low in calcium might help reduce the risk of kidney stones, right? Well, this particular study analyzed the diets of women and found that those with a higher amount of dietary calcium had a lower risk of kidney stones. This was attributed to the fact that calcium bonds with food-based oxalates in the intestine. Less oxalates were excreted, and therefore less were available to form stones.
What Treatments Are Available?
The majority of kidney stones will pass on their own. However, there are some cases where intervention is recommended. If a stone is too large to pass, if it is causing a dangerous blockage, or if there is heavy bleeding or infection, there are options. Open surgery used to be commonly performed under these circumstances, but other technologies are currently available. However, some of them are not without considerable side effects.
- Ureteroscopic stone removal: a small scope is passed through the ureter into the bladder and an attempt is made to snag the stone and remove it. During this process, ultrasound or lasers can be directed at the stone to break it up if necessary. This procedure is most successful on stones that have reached the lower part of the ureter. This is minimally invasive.
- Percutaneous nephrolithotomy: This involves inserting a small instrument called a nephroscope through an incision in the back. The stone is then removed. This is a more invasive procedure.
- Extracorporeal shock wave lithotripsy (ESWL): This is a relatively new procedure that is, in my opinion, “fraught with eminent peril.” Shock waves are used to break up the stones. Patients are sedated or partially anesthetized due to the pain of the shock waves. Ear protection must also be worn to protect from the loud noise of each shock wave. Subjects are placed in a water bath or on a soft cushion. X-rays are also used to locate the stone and monitor progress during the treatment. Possible side effects include: pain as the stone fragments are passed through the urinary tract (it can take months), blood in the urine, internal bleeding around the kidney and other organs, and bruises on the back and/or abdomen. Often a second round of ESWL treatment is ordered if the first one didn’t do the job. If all of this isn’t bad enough, a study released in 2006 states that treatment with ESWL increases the risks of developing hypertension and diabetes. I would definitely think twice before submitting to this treatment.