The kidneys are a pair of bean-shaped organs in the human body that play a critical role in maintaining overall health. They filter out waste products from the blood, regulate blood pressure, maintain electrolyte balance, and stimulate the production of red blood cells.

The kidneys are located in the retroperitoneal space on either side of the vertebral column, protected posteriorly by the 11th and 12th ribs. The right kidney sits slightly lower than the left owing to the presence of the liver superiorly. They are situated approximately at the level of the T12 to L3 vertebrae.

On average, an adult kidney measures about 10–12 centimeters in length, 5–7 centimeters in width, and 2–3 centimeters in thickness, with each weighing approximately 150 grams.

Features of Kidney Anatomy

The renal hilum is a vertical cleft on the medial border of the kidney where several structures enter and exit. These include the renal artery, renal vein, lymphatic vessels, and ureter. The renal artery delivers unfiltered blood to the kidneys, while the renal vein carries filtered blood away. The ureter transports urine from the kidney to the bladder.

The renal capsule is a thin, dense layer of fibrous connective tissue that surrounds each kidney. It provides protection against trauma and infection, maintains the kidney's shape, and contains the internal structures.

The renal fascia, also known as Gerota's fascia, is a layer of connective tissue encapsulating the kidneys and adrenal glands. It anchors the kidneys in place and separates them from surrounding organs.

The adipose capsule, or perirenal fat, is a layer of fatty tissue that surrounds the renal capsule. It acts as a protective cushion for the kidneys, absorbing shock from physical movements.

Common Disorders:

Several disorders can affect these layers of the kidney:

1. Renal Hilum: Disorders may include vascular conditions such as renal artery stenosis (narrowing of the renal artery) or renal vein thrombosis (clotting in the renal vein).
2. Renal Capsule: Infections can lead to a condition called perinephric abscess, where pus accumulates between the renal capsule and the kidney. This is often a complication of pyelonephritis.
3. Renal Fascia: Inflammation of this layer can result in perinephric fibrosis, leading to chronic pain and potential kidney damage.
4. Adipose Capsule: Obesity can cause an excessive buildup of fat around the kidneys, potentially leading to conditions like renal sinus lipomatosis.