Uric Acid, a Threat to Kidney

One of health problems often faced at the age of 30 years and over is high uric acid levels. This problem is often discovered only when conducting a health examination at a clinic or health facility. High uric acid level also often causes symptoms such as pain, swelling in the joints or a feeling of stiffness. In addition to these complaints, uric acid can also lead to kidney damage. Like an unbroken cycle, kidney damage also causes problems in uric acid discharge from the body and causes build-up. Therefore, it is important to know the relationship between blood uric acid levels and kidneys' health.

Uric acid is actually a waste product excreted by the body. In good body condition, this substance will normally be excreted by the kidneys and its levels in blood will be maintained in normal conditions of 3.5-7.0 mg/dL in males and 2.5-6.0 mg/dL in females. When uric acid production increases due to various reasons, symptoms of uric acid accumulation in the body may occur. This increase in production can be caused by the consumption of foods that contain excess purines or the destruction of excess cells in the body. If the condition of the kidneys is healthy, uric acid should not accumulate and be excreted in the urine. However, due to overproduction or poor excretion by the kidneys, high levels of uric acid can form crystals or deposits which are certainly harmful to the body.

Uric acid can be formed as a result of nucleic acid metabolism which can be found in DNA and RNA in all cells of the body. The products of this nucleic acid metabolism will be converted by the xanthine oxidase enzyme into uric acid. Because it is found in almost all cell nuclei, in the case of cancer patients undergoing chemotherapy, massive and rapid destruction of the cells causes uric acid levels to rise. However, in general, the cause of high uric acid levels is our own diet.

Some foods that we eat every day contain high levels of purines (https://www.verywellhealth.com/uric-acid-foods-5093036) and can cause an increase in uric acid in blood. The type of food in question includes red meat and offal such as liver, brain, tripe, lung, spleen, heart, and gizzard. For example, chicken liver contains 300 mg of purines per 100 grams of weight while beef contains 200 mg per 100 grams. In addition, seafood also has high levels of purines, such as sardines, mackerel, shrimp, shellfish, and anchovies. Of all the types of food mentioned earlier, anchovy has the highest purine content up to 1,100 mg per 100 grams of weight. These types of foods need to be watched out for and avoided so as not to cause an increase in uric acid levels in the body.

Hyperuricemia, or excess uric acid levels, is considered a risk factor for the progression of kidney disease. A study involving 3885 patients with stage 2-4 chronic kidney disease reported that uric acid was an independent risk factor for renal failure in early-stage chronic kidney disease, and had a 'J-shaped' association with mortality in chronic kidney disease (Srivastava et al. 2019, Am J Kidney Dis). If uric acid is supersaturated and crystallized in the urine, urinary tract stones will form so that the secretory and excretory system of kidney function is inhibited. The excretion of uric acid in the urine depends on several factors, such as blood uric acid level, glomerular filtration rate, and uric acid secretion by renal tubular epithelial cells into the urine. Uric acid is less saturated in acidic urine. When the urine pH rises, uric acid does not crystallize and will not form stones. Uric acid stones that form can clog the urinary tract and block urine flow, resulting in accumulation. This accumulation of urine will result in the enlargement of kidney and ureters, known as hydronephrosis and hydroureter. This condition causes acute kidney damage and is dangerous for the safe of the kidney. Interestingly, studies show that when experimental animals with chronic kidney disease are hyperuricemic, the preexisting kidney disease becomes more progressive, although crystal formation in the kidney does not occur. This means that uric acid can play a role in causing acute kidney damage through the formation of urate crystals and chronically, including through activation of oxidative stress and endothelial dysfunction resulting in increased intraglomerular and systemic pressure, accompanied by increased renal vascular resistance and decreased renal blood flow (Johnson, et al. 2013, Nephrol Dial Transplant).

When kidney function has decreased due to kidney failure, this condition causes kidney function to reduce uric acid metabolites, resulting in an accumulation of uric acid in the body. Treatment and management for kidney disease can help reduce the risk of impaired disposal of toxins in the body, including uric acid. If our body cannot discharge it through the kidneys, there will be an accumulation of uric acid crystals in the body. This will lead to complications of joint pain or kidney stones.

Thus, prevention of kidney disease with a healthy lifestyle and prevention of consumption of foods that contain excess purines can be important steps for us to prevent disturbances in our bodies. If you feel complaints of joint pain that are confirmed by high uric acid blood laboratory results, then consult your doctor for further evaluation. Your doctor will give you information, advice and treatment you need to help reduce the problem.[]


Djoko Santoso
Professor, Faculty of Medicine, Universitas Airlangga
Chairman of Health Department, Indonesian Council of Ulama, East Java