KIDNEY STONES & URETRAL STONES

Stone disease is among the most painful and prevalent urological disorders.  More than a million kidney stone cases are diagnosed each year with an estimated 10 percent of Americans destined to suffer from kidney stones at some point in their lives.

The incidence of urolithiasis, or stone disease, is about 12% by age 70 for males and 5-6% for females in the United States.  Additionally, the gender gap may be decreasing as more women are being diagnosed and treated for kidney stones.  The reason for the change is of the dietary and climate changes in our population.  The debilitating effects of kidney stones is quite substantial, with patients incurring billions of dollars in treatment costs each year.

Fortunately, most stones pass out of the body without any intervention. If you are not so lucky, the following information should help you and your doctor address the causes, symptoms and possible complications created by your kidney stone disease.

What are stones and the difference between kidney stones and ureteral stones?

Normally, urine contains many dissolved substances. At times, some materials may become concentrated in the urine and form solid crystals. These crystals can lead to the development of stones when materials continue to build up around them, much as a pearl is formed in an oyster. 

Stones formed in the kidney are called kidney stones.  Ureteral stone is a kidney stone that has left the kidney and moved down into the ureter.

The majority of stones contain calcium, with most of it being comprised of a material called calcium oxalate. Other types of stones include substances such as calcium phosphate, uric acid, cystine and struvite.

Stones form when there is an imbalance between certain chemical urinary components such as calcium, oxalate and phosphate.  These chemical components either promote crystallization while others inhibit it.

The most common stones contain calcium in combination with oxalate and/or phosphate.

A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the pure uric acid stones. Much rarer is the hereditary type of stones called cystine stones and even more rare are those linked to other hereditary disorders.

What happens under normal conditions?

The urinary tract, or system, consists of the kidneys, ureters, bladder and urethra. The kidneys are two bean-shaped organs below the ribs in the back of the torso (area between ribs and hips). They are responsible for maintaining fluid and electrolyte balance by removing extra water and wastes from the blood and converting it to urine.

The kidneys keep a stable balance of salts and other substances in the blood. They also produce hormones that build strong bones and help form red blood cells. Urine is carried by narrow muscular tubes to the ureters, from the kidneys to the bladder, a triangular-shaped reservoir in the lower abdomen. Like a balloon, the bladder's walls stretch and expand to store urine and then flatten when urine is emptied through the urethra to outside the body.  Normally, urine contains chemicals that prevent crystals from forming.

What are the risk factors for forming kidney stones?

For unknown reasons, the number of people in the United States with kidney stones has been increasing over the past 20 years. Caucasians are more prone to develop kidney stones than African Americans. Although stones occur more frequently in men, the number of women who get them has been increasing over the past 10 years, causing the ratio to change. If a person forms a stone, there is a 50 percent chance they will develop another stone.

Scientists do not always know what makes stones form. While certain foods may promote stones in susceptible people, researchers do not believe that eating specific items will cause stones in people who are not vulnerable. Yet factors such as a family or personal history of kidney stones and other urinary infections or diseases have a definite connection to this problem. Climate and water intake may also play a role in stone formation.

One of the main reasons stones forms is the loss of body fluids or being (dehydrated). When one does not consume enough fluids during the day, the urine can become concentrated and darker. This increases the chance that crystals can form from materials within the urine, because there is less fluid available to dissolve them. Stone formers should maintain 2 liters of urine output every day.  Also, a family history of stones, especially in a first-degree relatives (parent or sibling), dramatically increases the probability of having stones.

Diet can also affect the probability of stone formation. A high-protein diet can cause the acid content in the body to increase. This decreases the amount of urinary citrate, a "good" chemical that helps prevent stones. As a result, stones are more likely to form. A high-salt diet is another risk factor, as an increased amount of sodium passing into the urine can also pull calcium along with it. The net result is an increased calcium level in the urine, which increases the probability for stones. Intake of oxalate-rich foods such as leafy green vegetables, nuts, tea or chocolate may also worsen the situation.

Certain bowel conditions can also increase the risk such as chronic diarrhea, Crohn’s disease, and gastric bypass surgery. Obesity is also an independent risk factor for stone formation.

Although most stone formers do not have a medical condition that directly leads to their stone development, conditions do exist that place patients at high risk for stone formation. For example, stones can form because of obstruction to urinary passage like in prostate enlargement or stricture disease. Stone formation has also been linked to hyperarathyrodism, an endocrine disorder that results in more calcium in your urine. Susceptibility can also be raised if you are among the people with rare hereditary disorders such as cystinuria(formation of cystine stones in the kidneys, ureter, and bladder or primary hyperoxaluria (excessive urinary excretion of oxalate).  Development of kidney stones is due to the excess of the amino acid, cystine or the oxalate in your urine.

Another condition that can cause stones to form is absorptive hypercalciuria, a surplus of calcium in the urine that occurs when the body absorbs too much from food. Another condition that results in a high level of calcium in the urine is resorptive hypercalciuria where the kidney leaks calcium into the urine. The high levels result in calcium oxalate or phosphate crystals forming in the kidneys or urinary tract. Similarly, hyperuricosuria, excess uric acid tied to gout or the excessive consumption of protein-rich products, may also trigger kidney stones.

Consumption of calcium pills by a person who is at risk to form stones, certain diuretics or calcium-based antacids may increase the risk of forming stones by increasing the amount of calcium in the urine. Calcium oxalate stones may also form in people who have chronic inflammation of the bowel or who have had an intestinal bypass operation or ostomy. This is because of loss of more water from the body as well as absorption of oxalate from the intestine.

What are the symptoms of a kidney stone?

Once stones form in the urinary tract, they often grow with time and may change location within the kidney. Some stones may be washed out of the kidney by urine flow and end up trapped within the ureter or pass completely out of the urinary tract. Stones usually begin causing symptoms when they block the outflow of the urine from the kidney leading to the bladder because it causes the kidney to stretch.

Usually, the symptoms are extreme pain that has been described as being worse than child labor pains. The pain often begins suddenly as the stone moves in the urinary tract, causing irritation and blockage. Typically, a person feels a sharp, cramping pain in the back and in the side of the area of the kidney or in the lower abdomen, which may spread to the groin.

Sometimes a person will complain of blood in the urine, nausea and/or vomiting. Occasionally stones do not produce any symptoms. But while they may be "silent," they can be growing, causing irreversible damage to kidney function. More commonly, however, if a stone is not large enough to prompt major symptoms, it still can trigger a dull ache that is often confused with muscle or intestinal pain.

If the stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder. One may feel the need to urinate more often or feel a burning sensation during urination. In a man, pain may move down to the tip of the penis. If the stone is close to the lower end of the ureter at the opening into the bladder, a person will frequently feel like they have not fully completed urination.

Stones as small as 2 mm. have caused many symptoms while those as large as a pea have quietly passed. If fever or chills accompany any of these symptoms, then there may be an infection. You should contact your urologist immediately.

How are kidney stones diagnosed?

Sometimes "silent" stones, those that cause no symptoms are found on X-rays taken during a general health examination. These stones would likely pass unnoticed. If they are large, then treatment should be offered. More often, kidney stones are found on an X-ray or sonogram taken on someone who complains of blood in the urine or sudden pain. These diagnostic images give the doctor valuable information about the stone's size and location. Blood and urine tests also help detect any abnormal substance that might promote stone formation.

If your doctor suspects a stone but is unable to make a diagnosis from a simple X-ray, he or she may scan the urinary system with computed tomography (CT). CT is an imaging technique that is the gold standard for stone diagnosis as it is an extremely accurate diagnostic tool that can detect almost all types of kidney stones painlessly. Historically intravenous pyelorgram (IVP) was used but this requires prep as well as intravenous contrast dye and serial X-rays.

The abovementioned tests give your doctor information about the size, location and number of stones that are causing the symptoms. This allows the urologist to determine appropriate treatments.

How can kidney stones be prevented?

Unfortunately kidney stones are a recurrent disease, meaning that if you have one stone you are at risk for another stone event. In general, the lifetime recurrence risk for a stone former is thought to approach 50%. Stone prevention, therefore, is essential. Your doctor or urologist may follow up with several tests to determine which factors e.g., medication or diet should be changed to reduce your recurrence risk.

A good first step for prevention is to drink more liquids and water is the best. If you tend to form stones, you should try to drink enough liquids throughout the day to produce at least two liters of urine in every 24-hour period. People who form calcium stones used to be told to avoid dairy products and other foods with high calcium content. However, recent studies have shown that restricting calcium may actually increase stone risk.  High doses of calcium, Vitamin D, or Vitamin C may increase the risk of developing stones, especially in people with a family history of stones. These people need to be careful and should calcium supplementation be needed, calcium citrate is best.

If you are at risk for developing stones, your doctor may perform certain blood and urine tests to determine which factors can best be altered to reduce the risk. Some people can decrease their risk with dietary changes while others will need medicines to prevent stones from forming.

Other general recommendations for stone formers is that they consume a low sodium and low animal protein diet.

Do not be surprised, if you are asked to collect urine for 24 hours after a stone has passed or been removed to measure volume and levels of acidity, calcium, sodium, uric acid, oxalate, citrate and creatinine. This information will be used to determine the cause of the stone. A follow-up 24-hour analysis may be used to find out the effectiveness of treatment.

 

This information provided by the Urology Care Foundation at www.UrologyHealth.org