Hyperuricosuria

What is Hyperuricosuria?

Uric acid, a compound created from the breakdown of certain substances called purines, is produced in our bodies every day, about 300 – 400 mg of it. We produce most of it in the liver. Purines break down into substances named inosine and hypoxanthine. Then, we further break down hypoxanthine into xanthine and uric acid with the help of an enzyme called xanthine oxidase. In most animals, uric acid is transformed into a very soluble chemical called allantoin, which causes no harm to the body. But in humans, this transformation doesn’t happen because the required enzyme doesn’t work properly. As a result, the end product of purine breakdown in humans is uric acid, which isn’t very soluble. Therefore, high levels of uric acid in our urine and blood can lead to its accumulation in joints and kidneys which can cause medical conditions like gout and kidney stones. Foods like meat, fish, alcohol, sweet drinks, and certain organs in animals, which are high in purines, can also contribute to uric acid production in our bodies.

Our bodies get rid of uric acid mainly through the kidneys and intestines. In the intestines, we transform uric acid into ammonia and carbon dioxide. Bacteria in the intestine use this ammonia in their metabolic processes. As far as the kidneys are concerned, almost all of the uric acid is filtered initially. The kidneys then reabsorb the uric acid, attempt to get rid of it, but end up reabsorbing most of it again in a part of the kidney called the proximal convoluted tubule. Ultimately, only about 10% of uric acid is actually removed from the body through the urine.

The compound of uric acid was first identified by a Swedish pharmacist named Scheele back in 1776. Later, during the period of 1736 to 1802, a scientist named Fourcroy, who examined about 600 stones, also referenced uric acid.

What Causes Hyperuricosuria?

Uric acid kidney stones usually result from very acidic urine, too much uric acid in the urine, and not enough hydration. However, there are multiple factors involved in their formation.

There are some people who develop uric acid stones without a clear reason, a condition called idiopathic uric acid lithiasis. Their urine typically shows a low pH, meaning it’s very acidic, and a small amount of uric acid compared to an overly high level of uric acid in the blood. These characteristics are similar to a condition called primary gout, and so it’s believed that idiopathic uric acid lithiasis may be linked to this illness.

Around 10% to 20% of people with primary gout also develop uric acid kidney stones. These individuals have a urine profile similar to the idiopathic patients, with very acidic urine and a small amount of uric acid. The reason for the high blood uric acid level in these patients is a decreased uric acid excretion in urine. Factors such as drinking alcohol, consuming a diet high in fructose or animal protein can increase the risk for both gout and uric acid stones. Furthermore, people with conditions that include diabetes, large waist size, and high cholesterol due to insulin resistance – collectively known as metabolic syndrome – are more likely to form uric acid stones. It’s also been observed that the lower the urine pH (the more acidic it is), the higher a person’s body weight. This acidity is thought to result from a lack of buffering of urinary acid due to an impaired production of a buffering substance called ammonium.

People with bowel disorders like Crohn’s disease, and those who have a type of surgical opening in the belly called an ileostomy, are at higher risk for developing uric acid stones. These individuals often have chronic diarrhea, which can cause loss of bodily fluids and a specific ion, leading to low urine output and systemic metabolic acidosis (an overly acidic system).

There are genetic disorders that can lead to increased uric acid levels. These include Lesch-Nyhan syndrome, which is passed down from parent to child, and Type 1 collagen storage disorder. There are also some kidney diseases like Hartnup disease, Wilson’s disease, and familial hypouricemic hyperuricosuria, which can increase urinary uric acid output.

Diet, cancer, disorders that cause excessive growth of white blood cells, and certain drugs can also result in uric acid stones. These medications interfere with reabsorption of uric acid in the kidneys, leading to raised urinary uric acid and kidney stone formation. Patients with cancer tend to have high uric acid levels due to rapid cell turnover. They are especially predisposed to uric acid stone formation when they receive chemotherapy due to cell destruction.

Risk Factors and Frequency for Hyperuricosuria

Uric acid stones, which make up roughly 10% of all kidney stones in the United States, aren’t distributed evenly around the world. The occurrence of these stones can vary greatly based on things like ethnicity and geography. For example, over half the stones found in Hmong immigrants in the U.S. are uric acid stones and in countries like Sudan and Israel, they make up a staggering 57% and 75% of all stones, respectively. Women seem to develop them at a higher rate than men. Also, people with certain health conditions such as type 2 diabetes, metabolic syndrome, and obesity are far more likely to develop uric acid stones.

Your environment can also impact your risk. For example, a study in Saudi Arabia discovered a link between increased kidney stone pain and higher temperatures. Workers in hot factories were also found to form kidney stones at a higher rate. These findings suggest that dehydration plays a significant role in the formation of uric acid stones.

Recent research has shown an overall increase in the occurrence of kidney stones around the world, and these findings are particularly stark in developing countries. As the population in these countries becomes wealthier, they often shift to a diet containing more animal protein, which can lead to the creation of more uric acid. Similarly, global warming could be contributing to this increase. However, data on kidney stone prevalence in developing countries isn’t fully reliable: one study found conflicting evidence when looking at today’s Indian population versus past rates of kidney stone occurrence.

Signs and Symptoms of Hyperuricosuria

Nephrolithiasis, or kidney stones, is a condition which often leads people to seek emergency medical care because of intense lower abdomen and flank pain. The pain often spreads to the pubic area and even the genitalia as the stone moves through the ureter. The pain comes in waves and can be extremely severe, often accompanied by nausea or vomiting. A fever may also be present, particularly if the stone has caused an infection. It’s also common for patients with nephrolithiasis to have blood in their urine, visible to the naked eye or under a microscope, which helps confirm the condition.

It’s crucial to have a thorough medical history for any patient diagnosed with nephrolithiasis. Patients may have other conditions that influence stone development, such as gout or diabetes mellitus. Some medications taken by patients like probenecid or sulfinpyrazone can increase the level of uric acid in urine, which often relates to stone formation. Furthermore, their eating and drinking habits, such as animal protein intake, water intake, alcohol consumption, and consumption of fructose-containing foods, can have a significant impact on stone formation.

During a physical examination, nephrolithiasis patients typically present signs of significant discomfort because of the intense pain. They often squirm in pain, a sharp contrast to patients with acute abdomen pain who tend to keep still. They may also suffer from nausea and vomiting. They may show tenderness at the costovertebral area (where the rib cage meets the spine), but often, their abdominal examination does not reveal much. In patients suffering primarily from gout, tophi (hard uric acid deposits under the skin) may be visible.

Testing for Hyperuricosuria

If you’re suspected of having nephrolithiasis (also known as kidney stones), your doctor will start by getting a detailed history of your symptoms and doing a physical examination.

The next step usually involves a urine test, which can check for blood, crystals, and other signs of kidney stones. The testing also measures the pH level of your urine. For example, if the urine is acidic, it can suggest the presence of certain types of stones like uric acid stones. If the test indicates the possibility of an infection, further tests on your urine will be carried out. Also, note that seeing blood in your urine could be a sign of kidney stones, but it doesn’t confirm it absolutely. Only microscopic analysis can reveal urinary crystals that are not seen in basic tests. The shape of these crystals can indicate the type of kidney stones.

Blood tests are useful too. They can check the levels of various electrolytes and minerals including calcium, sodium, potassium, chloride, bicarbonate, and uric acid. If the levels of uric acid in your blood are high, it could imply an underlying condition called primary gout, and this increases the likelihood of uric acid kidney stones.

If you have a kidney stone, your doctor may recommend analyzing its chemical composition. This can help find the underlying cause and guide your treatment. Imaging tests, like a CT scan, can help identify and locate the kidney stones. Specifically, a CT scan without contrast is usually most helpful as intravenous contrast can make stones harder to see. If a CT scan isn’t available or it’s not suitable for you, a plain x-ray or an ultrasound can be used. Keep in mind that ultrasound can be particularly useful for pregnant women.

More in-depth tests may be required depending on your situation. For instance, if you have a higher risk of kidney stones due to a health condition, or if you’ve had kidney stones before, your doctor might ask for a 24-hour urine sample. This extensive testing checks for various substances in your urine that can contribute to stone formation. It’s especially important to do this if you’ve got a condition like intestinal malabsorption disorders, recurrent urinary tract infections, renal tubular acidosis, gout, diabetes mellitus, renal failure, high anesthesia risk, or if you’re a child, or if you have only one kidney.

Doing these detailed urine tests can provide a wealth of information. They can help determine what type of stones you’re forming, guide dietary changes, and identify specific issues that could direct treatment decisions. However, to successfully treat and prevent kidney stones, you’ll need to follow your doctor’s instructions closely. Although evaluating the results of the 24-hour urine test can be challenging, there are helpful guides available online to assist with understanding the results.

Treatment Options for Hyperuricosuria

Many individuals with kidney stones, a condition known as nephrolithiasis, may experience intense pain in their side, which is often accompanied by nausea and vomiting. This is referred to as acute renal colic, and managing this pain is a top priority. This can be achieved through various medications including Ketorolac, IV acetaminophen, lidocaine, and Diclofenac. If these are not effective, stronger pain medication like opioids can be used.

To diagnose kidney stones, medical professionals perform a urinalysis, which is a test of your urine, and a specialized CT scan of your abdomen and pelvis. They may also execute an abdominal x-ray to keep track of the stones over time and identify the type of stones you have.

In more serious cases, urgent intervention may be necessary. This can include procedures like a percutaneous nephrostomy or ureteral stenting. These treatments may be needed if there’s an infection or obstruction of the upper urinary tract, a risk of kidney failure, intense unmanageable pain or vomiting, or when a lone kidney is obstructed. In extreme circumstances, a percutaneous nephrostomy is usually the best option, as it allows for minimal interaction with the infected kidney.

If the stones are made of uric acid, there are specific management methods. Lifestyle changes including weight loss and reducing consumption of meat protein can help treat uric acid stones, as these stones are often linked to metabolic syndrome, diabetes, and insulin resistance. Drinking enough fluids to produce at least 2.5 liters of urine per day is also beneficial in inhibiting the formation of new stones.

There are also medical dissolution therapies that can treat uric acid kidney stones. These therapies aim to make your urine more alkaline, with the goal of achieving a urinary pH around 6.5. This technique can dissolve uric acid stones. An ultrasound can be used to monitor the therapy, and it is recommended to continue treatment even after the stones have dissolved to prevent new ones from forming.

Sodium and potassium bicarbonate salts are usually used to make the urine more alkaline. However, there can be downsides to these treatments, such as worsening certain medical conditions like hypertension, congestive heart failure, and cirrhosis due to fluid retention. Alternatives like acetazolamide can be utilized, which aids in urine alkalinization and reduces the excretion of urinary citrate. Certain food and drinks, for example, cocoa products that contain theobromine can also help alkalinize the urine and prevent the recurrence of uric acid stones.

After treatment, it is important for the patient to have regular imaging tests to monitor the stones and detect any complications. They may also be instructed to filter their urine to catch the stones for analysis. Generally, if the stones pass naturally within 4 to 6 weeks, further testing and specific preventive treatments will be recommended. However, if the stone is still present and hasn’t moved, surgical intervention, such as ureteroscopy with laser lithotripsy, may be necessary.

What else can Hyperuricosuria be?

When a patient arrives at the emergency room with abdominal pain, the doctors may consider various possible conditions, such as:

• Pyelonephritis (kidney infection)
• Ruptured ectopic pregnancy
• Appendicitis
• Aortic aneurysm rupture (a ruptured blood vessel in the stomach)
• Prostatitis (prostate inflammation)

They also consider different types of stones that might not show up on an X-ray, like:

• Xanthine stones – often found in people taking the medication allopurinol and who have high levels of uric acid in the blood.
• Matrix stones
• Ammonium urate stones – associated with overuse of laxatives
• Medication stones – typically formed by certain medications that can lead to urinary stones such as crixivan
• 2,8-dihydroxy adenine stones – usually found in patients with a deficiency of a specific enzyme (adenine phosphoribosyltransferase)

What to expect with Hyperuricosuria

If you have kidney stones, your doctor will want to follow up with you using imaging tests to check how your stones are doing. Generally speaking, 80% to 90% of stones that are 4 mm in size or smaller pass through your system on their own. However, the remaining ones that don’t move can cause complications like blockage, infection, abscesses in the kidney, rupture of the small organs (calices) in the kidney, formation of urine-filled cysts (urinomas), loss of kidney tissue, and narrowing of the tube that carries urine from the kidney to the bladder (ureteral strictures).

Uric acid stones are usually managed well by treatments that make the urine less acidic, but if the stone is larger than 10 mm, surgery may be needed. The underlying cause of the uric acid stones also affects how well they will respond to treatment.

Possible Complications When Diagnosed with Hyperuricosuria

Common risks and complications related to kidney and urinary issues include:

• Hydronephrosis, a condition where the kidneys are swollen due to inability to eliminate urine
• Obstructive pyelonephritis, a severe kidney infection that can occur when there’s a blockage—like a stone—in the organ
• Recurrent urinary tract infections, which are frequent infections in your urinary system, including your kidney, bladder, and tubes that carry urine
• Ureteral perforation, which is a hole in the tube that carries urine from the kidney to the bladder
• Caliceal rupture with urinoma formation, which is a kidney disorder that’s a result of the ropture of the renal calyces leading to pooling of urine
• Ureteral strictures, which is a narrowing of the ureters that can slow or block the flow of urine to the bladder
• End-stage renal disease, which is the last stage of chronic kidney disease when the kidneys no longer function as they should
• Chronic kidney disease, which is when your body’s kidneys gradually stop working over time
• Stone recurrences, or occurrences of multiple stones in the kidney or bladder

Preventing Hyperuricosuria

Patients who have uric acid stones, a type of kidney stone, should embrace a healthier lifestyle to avoid the formation of more stones. These stones are often linked to resistance to insulin (a hormone that regulates blood sugar) and excessive body weight. Therefore, it’s crucial to make changes to your diet, weight, and level of physical activity.

Begin by altering your food habits. Try to lessen the amount of animal protein you consume, as well as foods high in fructose (a type of sugar) and salt. Ensuring you drink enough fluids is also critical because it can help prevent the urine from becoming overly saturated with waste products that form stones.

It’s also essential that you understand how to recognize if complications arise. If you encounter symptoms such as a high temperature or an inability to urinate (anuria), you should seek medical attention immediately.

Patients who are at a high risk of developing stones, or those who are especially determined to prevent stones, should consider a 24-hour urine test. This test can pinpoint specific risk factors that can be controlled to reduce the likelihood of stones recurring in the future.