The term “renal” is the medical descriptor for everything related to the kidneys, the body’s sophisticated waste management and fluid regulation organs. These two fist-sized organs are central to survival and internal balance. This article defines the term and explains the complex roles the kidneys play within the body.
Defining the Renal System
The word “renal” means “relating to the kidneys.” These organs are located high in the abdominal cavity, situated near the back, just below the rib cage. Each kidney has a distinct, reddish-brown, bean-like shape. Blood enters through the renal artery for filtering and returns cleaned via the renal vein.
Collectively, the kidneys, along with the tubes that carry urine away, form the renal or urinary system. This system includes the two ureters, which transport urine, the bladder, which stores it, and the urethra, through which urine exits the body. The specialized field of medicine dedicated to the study of kidney function and disease is known as nephrology.
Essential Functions of the Kidneys
The primary role of the kidneys is to act as the body’s nonstop filtration and recycling plant for the blood. Approximately 20% of the blood pumped by the heart enters the kidneys every minute, filtering about 200 quarts of fluid daily. Most of this fluid is cleaned and returned to the body; only a small fraction becomes urine.
The functional unit of filtration is the nephron, a microscopic structure of which each kidney contains about a million. Within the nephron, blood is filtered in the glomerulus, a cluster of tiny blood vessels. Smaller molecules and waste pass through, and the remaining fluid travels through renal tubules. Here, substances the body needs, such as water, glucose, and essential minerals, are reabsorbed back into the bloodstream.
This process ensures the removal of metabolic waste products, such as urea, a nitrogenous byproduct of protein breakdown, and creatinine, a waste product from muscle activity. The kidneys maintain homeostasis by regulating the balance of water and electrolytes, including sodium, potassium, and calcium, in the blood. They also maintain the body’s acid-base balance.
Beyond filtration, the kidneys perform endocrine functions by regulating hormones. They produce erythropoietin, which stimulates the bone marrow to produce red blood cells. They also produce renin, a substance that helps regulate blood pressure, and activate a form of vitamin D necessary for bone health.
Understanding Common Renal Conditions
When the renal system malfunctions, it loses its capacity to perform essential functions, leading to the buildup of waste and fluid. Chronic Kidney Disease (CKD) is the progressive loss of kidney function, often caused by conditions like diabetes or high blood pressure that damage the filtering units. If CKD progresses to end-stage renal disease, the patient requires mechanical filtering, such as dialysis, or a kidney transplant.
Another common issue is the formation of kidney stones, or renal calculi, which are hard deposits of minerals and salts. These stones can cause intense pain if they block the flow of urine while passing through the ureters. Renal infections, such as pyelonephritis, are also a concern, as bacteria can travel up the urinary tract and cause damage to the kidney tissue.
Polycystic Kidney Disease (PKD) is a genetic disorder where fluid-filled cysts grow on the kidneys, gradually compromising the organ’s ability to filter blood. Any condition that impairs kidney function directly impacts the body’s ability to clean blood, regulate blood pressure, and maintain proper electrolyte balance.