Kidney Function Tests

Kidney function tests are a series of lab tests used to assess kidney function. The kidneys play a vital role in filtering waste products from the blood and excreting them through urine. When kidneys fail to function properly, this can lead to buildup of waste products in the blood, which can cause serious health problems. 

In this blog, we will discuss the kidney functions, the symptoms of kidney diseases, the types of kidney function tests and when they should be performed, and we will also give some guidelines for protecting our kidneys.

The Kidney functions

The human body contains two bean-shaped kidneys located in the upper abdomen, on either side of the spine, and are responsible for many biological functions which include:

1. Waste excretion:
 The primary function of the kidney is to filter waste products and excess fluids from the blood and remove toxins and other harmful substances that accumulate in the body, such as urea, creatinine, and uric acid. 

2. Regulation of Blood Pressure:
 One of the most critical functions of the kidneys is regulating blood pressure through production of a hormone called renin, which helps to control blood pressure by constricting or dilating blood vessels.

3. Production of Red Blood Cells:
 The kidneys also play a vital role in the production of red blood cells through excretion of erythropoietin hormone, which stimulates the bone marrow to produce red blood cells and its deficiency can lead to anemia.

4. Maintenance of Acid-Base Balance:
The kidneys help to maintain the body’s acid-base balance by excreting hydrogen ions and reabsorbing bicarbonate ions. They are also responsible for regulating the level of other electrolytes, such as potassium and calcium, which are critical to the body’s acid-base balance.

Symptoms of Kidney Disease

An early-stage kidney disease may not have any symptoms, however; some symptoms appear at later stage and indicate a kidney disease which include:

1. high blood pressure
2. blood in urine
3. frequent and painful urination
4. swelling of hands and feet 
5. Weight loss
6. Headache and tiredness
7. Shortness of breath
8. Muscle cramps

Causes of Kidney Diseases

There are some factors which increase the risk of chronic kidney disease which include:

1. High Blood Pressure:
2. Diabetes
3. Glomerulonephritis
4. Urinary flow blockage
5. High Cholesterol level
6. A genetic disorder called Polycystic Kidney Disease:
7. Long term use of some medications

Types of Kidney Function Tests

Urine Tests

The following  kidney function tests can be performed in urine to evaluate kidney functions:

• Urine analysis: Urine analysis is a simple test that checks the urine for abnormalities, such as: excessive protein, blood cells, sugar, and pus cells, which can all be signs of kidney disease.
• Urine 24-hour Protein Test: This test measures the amount of protein in a 24-H urine sample. High levels of protein in urine can indicate kidney damage.
• Microalbuminuria: This test is used to detect tiny amounts of protein called albumin in urine. It should be performed for people who have high risk of kidney disease such as: diabetic patients and patients with hypertension.
• Albumin/ Creatinine ratio: It is used to measure how the kidneys are working and is calculated by dividing albumin level to creatinine level. 
• Creatinine Clearance: In this test creatinine level in 24-H urine sample is compared to creatinine in serum to evaluate the efficiency of the kidney to filter out waste products.

Blood Tests

Some kidney function tests can be performed in blood to assess kidney function. The following blood tests are commonly used:

• Serum Creatinine Test: This test measures the level of creatinine in the blood, which is the waste product of energy production from body muscles. High levels of creatinine can indicate kidney dysfunction.
• Blood Urea Nitrogen (BUN) Test: This test measures the level of urea nitrogen in the blood which comes from the breakdown of food proteins. High levels of BUN can indicate kidney dysfunction.
• Uric acid: This test measures the amount of uric acid that our body makes when it breaks down chemicals called purines, which are found in high amounts in red meat and beans. Although uric acid is used mainly to diagnose gout, its level may increase in kidney disorders.
• Glomerular Filtration Rate (GFR): GFR is a calculated value based on serum creatinine level, age, sex, weight and race. It is used to estimate the efficacy of the kidney to remove wastes and excess fluid from the body.

When Should Kidney Function Tests be Performed?

Kidney function tests should be performed for many reasons which include:

• As a part of routine health screening to make sure that our kidneys work properly.
• When a person has symptoms of kidney disease.
• In patients with chronic disorders which affects kidney functions such as diabetes and hypertension
• When a person has a family history of diabetes or hypertension.
• When a person is taking medications that can affect kidney function.

How to protect the kidney

There are some guidelines that should be followed to protect our kidneys:

1. Maintain a Healthy Lifestyle:
   Eating a healthy diet, exercising regularly, and maintaining a healthy weight can help protect our kidneys. 
2. Manage Medical Conditions:
   Some medical conditions such as: diabetes or high blood pressure should be managed properly, and kidney function tests should be monitored regularly to prevent kidney damage. 
3. Stay Hydrated:
   Drinking plenty of water can help flush out waste products from the body and keep the kidneys healthy. It is recommended to drink at least 8-10 glasses of water per day.
4. Avoid Overuse of Painkillers:
   Overuse of painkillers can cause kidney damage. It is important to follow the recommended dosage and avoid using painkillers for an extended period of time.
5. Quit Smoking:
   Smoking can damage blood vessels and decrease blood flow to the kidneys, which can lead to kidney damage. 
6. Quit Alcohol Consumption:
   Excessive alcohol consumption can lead to high blood pressure and liver damage and may also contribute to kidney damage.

References

1. Saydah SH, Pavkov ME, Zhang C, et al. Albuminuria prevalence in first morning void compared with previous random urine from adults in the National Health and Nutrition Examination Survey, 2009–2010external icon. Clin Chem. 2013;59(4):1–9.
2. Collins AJ, Vassalotti JA, Wang C, et al. Who should be targeted for CKD screening? Impact of diabetes, hypertension, and cardiovascular disease.external iconAm J Kidney Dis. 2009;53(3 Suppl 3):S71–77.
3. Vassalotti JA, Fox CH, Becker BN. Risk factors and screening for chronic kidney disease.external iconAdv Chronic Kidney Dis. 2010;17(3):237–245.
4. Chu CD, McCulloch CE, Banerjee T, Pavkov ME, Burrows NR,Gillespie BW, Saran R, Shlipak MG, Powe NR, Tuot DS; Centers for Disease Control and Prevention Chronic Kidney Disease Surveillance Team. CKD awareness among US adults by future risk of kidney failure.external icon Am J Kidney Dis. 2020 Aug;76(2):174–183.
5. Chu CD, Powe NR, McCulloch CE, Crews DC, Han Y, Bragg-Gresham JL, Saran R, Koyama A, Burrows NR, Tuot DS; Centers for Disease Control and Prevention Chronic Kidney Disease Surveillance Team. Trends in chronic kidney disease care in the US by race and ethnicity, 2012-2019external icon. JAMA Netw Open. 2021 Sep 1;4(9):e2127014.