Uric acid stones are one of four major types of kidney stones.
Uric acid stones are one of four major types of kidney stones, which include calcium stones (calcium oxalate and calcium phosphate), struvite stones, and cystine stones.
A kidney stone is a hard mass of crystallized minerals that form in the kidneys or urinary tract.
Estimated that one in 10 people in the U.S. will have a kidney stone of one kind or another at some time in their lives.
Uric acid stones occur in 10% of all kidney stones and are the second most-common cause of urinary stones after calcium oxalate and calcium phosphate calculi.
About 8.8% of the population has kidney stones.
Among men, the lifetime risk pf kidney stones is about 19%, and in women, it is 9%.
The first incidence of kidney stones occurs after age 30.
Many cases occur sooner than age 30, and stones occur in some children as young as five years of age.
Uric acid stones form when the levels of uric acid in the urine is too high, and/or the urine is too acidic (pH level below 5.5) on a regular basis.
The most important risk factor for uric acid crystallization and stone formation is a low urine pH, below 5.5, rather than an increased urinary uric acid excretion.
High acidity in urine is linked to:
Inherited problems in how the body processes uric acid or protein in the diet can increase the acid in urine-gout.
Uric acid can result from a diet high in purines, which are found especially in animal proteins such as beef, poultry, pork, eggs, and fish.
The highest levels of purines are found in organ meats, such as liver and fish.
Main causes of low urine pH are tubular disorders, including gout, chronic diarrhea or severe dehydration.
Diet alone is not the cause of uric acid stones.
There is an increased risk of uric acid stones in obesity or diabetes.
Patients on chemotherapy are prone to developing uric acid stones.
Symptoms of uric acid stone:
Pain in the lower back, sides, abdomen or groin; the pain is the result of irritation or blockage inside the kidneys or urinary system.
Blood in the urine
Nausea or vomiting
Fever and chills
Urine that smells bad or is cloudy during a urinary tract infection
Stones may be removed from the kidney or urinary tract by the following minimally invasive surgical techniques:
Shockwave lithotripsy
A tiny scope is used to enter the ureter and/or kidney through the urethra and breaking up the stone with a laser.
Larger stones in the kidney can be removed through percutaneous nephrolithotomy (PCNL), which involves making a 1cm incision in the back and removing stones through a hollow, direct tract into the kidney.
Urine collection over a 24-hour period can determine the abnormal components in the urine and how much urine is being passed per day.
If the urine volume is too low, the patient will be encouraged to drink more liquids to reach a target urine volume of 2.5L/day.
Stones smaller than seven millimeters (7 mm) in diameter may pass on their own with time.
Alpha blockers may encourage the passage of stones located in the lower ureter.
Drinking more fluids is the most important step in treatment.
Higher levels of fluids reduce concentration of minerals in urine, and encourage urination which can flush away materials that might form stones.
It is recommended that a person drink enough fluid each day to produce about 2.5 liters of urine.
This usually requires intake of about three liters (3.1 quarts) of fluids per day, since some may be lost through sweating, particularly in hot weather, or as a result of work or exercise.
The best fluid to drink is water, but hard water with high calcium content and soft water with high sodium content are best to avoid because they add extra minerals to urine.
In cases of stones that are large and block the flow of urine, cause infection, or have not passed after four to six weeks, surgery may be needed to remove them.
Once a stone is found, the risk of having another is about 50% in the next five to seven years.
Prevention:
Drinking at least three quarts (12 cups) of fluids daily; water is best.
Decrease intake of red meats and shellfish, replacing them with more fruits and vegetables, low-fat dairy products, and whole grains.
Limit the amount of alcohol.
Achieve or maintain a healthy weight.
Avoid crash dieting, which increases uric acid levels in the blood.
Follow the Dietary Approaches to Stop Hypertension (DASH) diet, which has been shown to reduce not only high blood pressure but also the risk of kidney stones.
Prescribed medications to prevent uric acid stones and keep them from coming back.
The treatment of uric acid stones consists not only of hydration (urine volume above 2000 ml daily), but mainly of urine alkalinization to pH values between 6.2 and 6.8.
Urinary alkalization with potassium citrate or sodium bicarbonate is a highly effective treatment, resulting in dissolution of existing stones.
Urinary uric acid excretion can be reduced by a low-purine diet.
Potassium citrate is the treatment of choice for the prevention of recurrence of uric acid calculi.
Allopurinol reduces the frequency of stone formation in hyperuricosuric patients with recurrent uric acid stones and/or gout.