Kidneys: where they are located, how they are structured and what functions they perform

The kidneys are a paired organ of the urinary system that filters blood and removes metabolic products and excess water from the body. Understanding where the kidneys are located, what they consist of and what tasks they perform helps to correctly interpret test results and a doctor's explanations.

Where the kidneys are located in humans

There are two kidneys, each about the size of a fist. They are located closer to the middle of the back, just under the rib cage, outside the abdominal cavity — behind its posterior wall. In front they are covered by the abdominal organs, behind by the back muscles and lower ribs, so normally the kidneys cannot be felt through the anterior abdominal wall.

Left and right kidney: location

The kidneys lie on both sides of the spine and are not mirror images of each other. The right kidney is usually located slightly lower than the left: above it is the liver, which occupies a significant part of the right hypochondrium. The left one is adjacent to the spleen and the tail of the pancreas. A small difference in level is a variant of the norm, not a sign of disease.

Kidney structure: the kidney in cross-section

Inside each kidney there are about a million microscopic structures — nephrons. They are what filter the blood, retaining metabolic products and excess water: this is how urine is formed. In cross-section, an outer layer is visible where the vascular glomeruli of the nephrons are located, and an inner layer where urine collects in the renal calyces and pelvis. Most kidney diseases affect the nephrons, and then the organ loses its ability to remove metabolic products.

Ureter: how urine is removed from the kidney

From the pelvis, urine passes into the ureter — a tube that connects the kidney to the bladder. The bladder accumulates urine until urination. Impaired urine outflow — recurrent stones, an enlarged prostate — is among the causes of chronic kidney disease.

Functions of the kidneys in the body

• Filtering blood and removing metabolic products and excess water.
• Formation of urine.
• Transport of urine through the ureters to the bladder, where it accumulates.

The condition of the kidneys is linked to the work of the heart and blood vessels: in chronic kidney disease the risk of heart attack and stroke increases, and cardiovascular diseases remain one of the main causes of death in such patients.

When to see a doctor about the kidneys

In the early stages, kidney disease usually produces no symptoms: it is detected by blood or urine tests ordered for another reason. At a later stage, fatigue, swelling of the feet, ankles or hands, shortness of breath, nausea, and blood in the urine appear. See a doctor if you have persistent or alarming symptoms that could be linked to the kidneys. Diagnosis relies on blood and urine tests: their results determine the stage — a number reflecting the severity of kidney damage.

Causes of chronic kidney disease include high blood pressure, diabetes, high cholesterol, kidney infections, glomerulonephritis, polycystic disease, impaired urine outflow and long-term use of certain medications. The process develops over years and reaches complete loss of kidney function in about 2 out of 100 patients; most people live with the disease for many years, receiving treatment and regular check-ups.

Kidney disease by itself is not a reason to call an ambulance. The numbers 103 or 112 — if there are signs of a heart attack or stroke, as well as another life-threatening condition.

This material is for reference purposes and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer