The kidneys and liver are essential organs that play crucial roles in maintaining overall health and wellbeing. The kidneys filter waste, regulate fluid balance, and support other vital functions, while the liver plays a central role in metabolism, detoxification, and nutrient storage. Both organs can be affected by various diseases that can disrupt their normal functions, leading to serious health complications. In this article, we will explore the key functions of the kidneys and liver, common diseases that can impact them, and ways to maintain their health.

Kidney Function

The body contains two kidneys, each roughly the size of an adult’s fist, located on either side of the spine beneath the rib cage.¹

The kidneys remove acid to help maintain a healthy balance of water, salt, and minerals in the blood. They also produce hormones that regulate blood pressure, stimulate red blood cell production, and support bone health.² 

Blood flows to the kidneys through an artery, where it is filtered. Waste then travels through the ureter to be stored as urine in the bladder. Once the blood is filtered, it returns to the bloodstream. When the bladder is full, urine exits the body through the urethra.¹ 

The kidneys filter about half a cup of blood per minute, removing waste and excess water to produce urine. This urine then flows from the kidneys to the bladder via the ureters.²

The kidneys perform their vital function by filtering and returning approximately 200 quarts of fluid to the bloodstream every 24 hours. Of this, about two quarts are excreted as urine, while the rest is retained in the body.¹

Kidney Diseases

Chronic kidney disease. Chronic kidney disease (CKD) occurs when the kidneys are damaged and cannot filter blood effectively. Risk factors for CKD include type 2 diabetes, high blood pressure, heart disease, and a family history of kidney failure. Preventive measures include eating a healthy diet, staying physically active, and maintaining a healthy weight. In severe cases, CKD may lead to kidney failure, which might require dialysis or a kidney transplant.³ 

Kidney stones. Kidney stones are solid, pebble-like deposits that form when certain minerals build up in the urine. Symptoms often include sharp pain in the back, side, or abdomen, and blood in the urine. Kidney stones can be removed by a healthcare professional, and if caught early, they are less likely to cause long-term problems. To prevent kidney stones, it’s important to drink plenty of water, eat a balanced diet, and, if necessary, take medications that help reduce the risk of stones.⁴

Liver Functions

The liver plays a crucial role in metabolism, immune function, digestion, and detoxification.⁵ 

The liver is made up of small units called lobules, which consist of liver cells. Blood and bile flow through channels within these cells. Blood from the digestive organs enters the liver through the portal vein, carrying nutrients, medications, and toxins. In the liver, these substances are processed, stored, detoxified, and either re-released into the bloodstream or passed into the bowel for elimination.⁶ 

The liver also plays a key role in various metabolic processes. It stores vitamins and minerals, breaks down fats for energy, and helps regulate blood sugar levels. After a meal, when blood sugar levels rise, the liver removes excess sugar from the blood and stores it as glycogen. If blood sugar levels drop, the liver breaks down glycogen and releases sugar back into the bloodstream.⁶ 

Liver Diseases

Cirrhosis. Cirrhosis, or hepatic fibrosis, is scarring of the liver caused by long-term damage or disease. A liver with scar tissue cannot function properly. Symptoms of cirrhosis may include easy bruising, bleeding, swelling of the abdomen or legs, high blood pressure, and enlarged veins.⁷

The most common causes of cirrhosis are chronic alcoholism and hepatitis. Treating the underlying cause can help prevent further damage and the growth of additional scar tissue. In severe cases, a liver transplant may be necessary.⁷ 

Fatty liver disease. Fatty liver disease occurs when excessive fat accumulates in the liver. The two main types are alcoholic fatty liver disease and nonalcoholic fatty liver disease.⁸

Alcoholic fatty liver disease is caused by heavy alcohol use. When the liver breaks down alcohol, it can create harmful substances that damage liver cells, cause inflammation, and impair liver function.⁸ 

Nonalcoholic fatty liver disease has no clear cause, but it is more common in people with type 2 diabetes, obesity, high blood pressure, and metabolic syndrome.⁸ 

Both alcoholic and nonalcoholic fatty liver diseases often present with no symptoms. If symptoms are present, individuals usually experience tiredness and abdominal pain. 

Both nonalcoholic fatty liver and alcoholic fatty liver diseases are usually silent diseases with few or no symptoms. If you do have symptoms, you may feel tired or have discomfort in the upper right side of your abdomen.⁸

Diagnostic Tests

Blood tests such as a comprehensive metabolic panel are ordered by healthcare providers to assess kidney and liver functions. This test measures the following: the amounts of protein in the blood, produced by the liver; levels of bilirubin, a waste formed when the body breaks down old red blood cells, which the liver removes; and levels of blood urea nitrogen and creatinine, waste products filtered out through the blood by the kidneys. This preventive blood test offers insight into kidney and liver function and can help detect early-stage complications.⁹

The Bottom Line

If you have concerns about your kidney or liver health, speak with your primary care provider about ways to preserve your kidney and liver functions, and what you can do to prevent and decrease the risk of developing future complications associated with kidney and liver diseases.

Sources

1. National Kidney Foundation. How your kidneys work. 2015. Accessed 22 Nov 2024. https://www.kidney.org/kidney-topics/how-your-kidneys-work
2. National Institute of Diabetes and Digestive and Kidney Diseases. Your Kidneys & How They Work. Reviewed Jun 2018. Accessed 11 Nov 2024. https://www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work 
3. National Institute of Diabetes and Digestive and Kidney Diseases. Chronic Kidney Disease (CKD). Reviewed Oct 2016. Accessed 2 Dec 2024. https://www.niddk.nih.gov/health-information/kidney-disease/chronic-kidney-disease-ckd
4. National Institute of Diabetes and Digestive and Kidney Diseases. (Kidney stones) Reviewed May 2017. Accessed 2 Dec 2024. https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-stones
5. Kalra A, Yetiskul E, Wehrle CJ, et al. Physiology, Liver. [Updated 2023 May 1]. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK535438/
6. InformedHealth.org. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. In brief: How does the liver work? [Updated 2023 Feb 28]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279393/
7. Medline Plus. (Cirrhosis). Updated 1 Nov 2016. Accessed 2 Dec 2024. https://medlineplus.gov/cirrhosis.html
8. Medline Plus. Fatty Liver Disease. Updated 26 Apr 2017. Accessed 2 Dec 2024. https://medlineplus.gov/fattyliverdisease.html
9. Medline Plus. Comprehensive Metabolic Panel (CMP). Updated 4 Dec 2023. Accessed 11 Nov 2024. https://medlineplus.gov/lab-tests/comprehensive-metabolic-panel-cmp/