Renal Cortex

What is the renal cortex?

The cortex is the outside layer or covering of many body organs, so the renal cortex is the outer layer of the kidney. The renal cortex is also known as the kidney cortex. The cortex surrounds the inside of the organ, which is called the medulla. The renal cortex itself is covered by the renal capsule, which is a layer of tougher protective tissue.

The renal cortex is where the nephrons (blood-filtering units) begin. Each kidney has 1 million nephrons. The filtering unit of the nephron is the glomerulus, and the glomerulus is attached to a tubule which removes wastes and returns the needed substances to your body. In the renal cortex, the tubules are twisted (convoluted), while in the medulla the tubules are straighter.

What does the renal cortex do?

As part of your urinary tract, the renal cortex is involved in kidney functioning. Kidneys are important for their many jobs, not just getting rid of body wastes. They also control:

• The balance of electrolytes and water.
• Your body’s blood pressure and amount of extracellular fluid (outside the cells).
• Red blood cell production.
• The balance between acids and bases.
• Vitamin D production.
• The balance between calcium and phosphate.
• Production of glucose (glucogenesis). Your liver makes most of the glucose (sugar) you need, but some is made in the kidneys.

Where is the renal cortex?

The renal cortex is part of your kidney, which itself is part of the urinary tract. Kidneys are located just below your ribcage and behind your belly. Typically, one kidney sits on either side of your spine. The kidneys are located between your intestines and your diaphragm. Each kidney has a tube-like structure called the ureter which connects the kidney to your bladder.

The renal cortex is brownish-red in color. It’s the outside part of the kidney. It covers the renal medulla, the inside part of the kidney. The medulla contains little triangular pieces called the renal pyramids. The renal cortex covers the renal pyramid like a cap.

What are the common conditions and disorders that affect the renal cortex?

Many different disorders can affect the kidneys, including:

• Chronic kidney disease: Chronic kidney disease (CKD) may lessen your kidney function. Diabetes or high blood pressure usually causes CKD.
• Kidney cancer: Renal cell carcinoma is the most common type of kidney cancer.
• Kidney failure (renal failure): Kidney failure may be acute (worsen suddenly) or chronic (a permanent lessening of how well your kidneys work). End-stage renal disease is a complete loss of kidney function. It requires dialysis (treatment to filter your blood in place of your kidneys).
• Kidney infection (pyelonephritis): A kidney infection can occur if bacteria enter your kidneys by traveling up your ureters. These infections cause sudden symptoms. Healthcare providers treat them with antibiotics.
• Kidney stones: Kidney stones cause crystals to form in your urine and may block urine flow. Sometimes these stones pass on their own. In other cases, healthcare providers can offer treatment to break them up or remove them.
• Kidney (renal) cysts: Fluid-filled sacs called kidney cysts grow on your kidneys. These cysts can cause kidney damage. Healthcare providers can remove them if medically indicated.
• Polycystic kidney disease: Polycystic kidney disease (PKD), a genetic condition, causes cysts to form on the kidneys. PKD may lead to high blood pressure and kidney failure. People with PKD need regular medical monitoring.

There are so many other disorders that can affect or be related to your kidneys, and many of them are serious. Some of these conditions include:

• Acidosis: Excess acid accumulates in your blood if your kidneys are not functioning well, which can cause many health problems. It can become life-threatening if it is severe and left untreated.
• Acute or chronic interstitial nephritis: Your kidneys become inflamed, which may lead to kidney failure.
• Diabetic nephropathy or hypertensive nephropathy: High blood pressure and uncontrolled blood sugars causes kidney damage. This is also called nephropathy.
• Glomerular diseases: Your glomeruli become inflamed or damaged due to glomerular diseases. The condition can potentially lead to kidney failure.
• Minimal change disease: This is a kidney disease in which there is a damage to the glomeruli leading to large amounts of proteins lost in urine (pee).
• Proteinuria and nephrotic syndrome: Proteinuria means you have high levels of protein in your urine (pee). It can be a sign of kidney damage. Very high levels of proteins in the urine can be a sign of nephrotic syndrome where the injured glomeruli leaks lots of blood proteins in your urine.
• Uremia: Toxins that are normally cleared by your kidneys and go out in your urine build up in your bloodstream instead. Uremia can be life-threatening if not treated.

What are some common signs or symptoms of diseases related to the renal cortex?

Most kidney problems don’t have symptoms in the early stages. As kidney damage progresses, you may notice:

• Cramping muscles: Electrolyte imbalances can cause your muscles to stiffen. Most of the time, the calf muscle (the muscle on the back of your leg, underneath the knee) is affected, but it can involve any group of muscles.
• Dark urine or urine with blood in it: Damage to your kidneys’ filters lets red blood cells leak into your urine (pee). This is called hematuria.
• Foamy urine: Bubbles in your pee can signal excess protein.
• Itchy, dry skin: An imbalance of minerals and nutrients in your blood leads to itchy skin.
• More frequent urination: Problems filtering some waste products can cause you to pee more often.
• Puffy eyes or swollen ankles and feet: Reduced kidney function can cause your body to hold onto protein and sodium, leading to edema (swelling due to fluid retention).
• Sleep problems, fatigue and lack of appetite: If toxins build up in your blood, your sleep, appetite and energy levels may be off.

What are common tests to check the health of the renal cortex?

Healthcare providers use several tests to measure kidney function and diagnose kidney problems. Your provider may recommend:

• Imaging tests (X-ray, CT scan, MRI, ultrasound or nuclear medicine imaging): These tests can show kidney abnormalities or obstructions (blockages). For instance, these can show the thickness of the renal cortex. Thinning of the cortex may mean that the kidney has been injured.
• Blood tests: These can show how well your glomeruli filter your blood.
• Kidney biopsy: In this test, your provider removes a small amount of kidney tissue to examine under a microscope.
• Ureteroscopy: This is a test where your provider passes a tube (endoscope) through your urethra into your bladder and ureters to look for abnormalities.
• Urinalysis: This measures specific substances, such as protein or blood, in urine to detect any abnormality that may indicate a disease condition or infection.
• Kidney function tests (also called renal function tests): These tests show how well the kidneys are working. One of the blood tests is called “creatinine” which can estimate kidney function and assess how efficiently your kidneys are clearing wastes from your blood.

What are some common treatments for the renal cortex?

Treatments for disorders that affect your kidneys and renal cortex depend on the condition you have. For instance, if you have infections, your provider will prescribe antibiotics.

If you have something that needs to be removed, you may need a procedure or surgery. This could be true if you have a kidney stone, or a cyst or cancer.

How can I keep my kidneys healthy?

It’s important to have regular checkups where your provider can order blood and urine tests to measure your kidneys’ health, especially if you have issues like high blood pressure, obesity and diabetes. You can reduce your risk of developing a kidney problem by:

• Avoiding or quitting smoking.
• Cutting out excess salt, which can affect the balance of minerals in your blood.
• Drinking lots of water, which can help your kidneys get rid of toxins.
• Increasing daily exercise, which can reduce high blood pressure.
• Limiting your use of nonsteroidal anti-inflammatory drugs, substances that can cause kidney damage when overused.
• Maintaining a healthy weight.
• Monitoring your blood pressure, frequently allowing more opportunities to detect higher levels than the desired range.
• Watching your blood sugar levels aiming for well-controlled diabetes.

What is the difference between the renal cortex and the renal medulla?

The kidney is made up of solid tissue called parenchyma which consists of cortex and the medulla. The renal cortex is the outside section of the kidney, while the medulla is the inside section.

The renal cortex has a more grainy texture, while the medulla is smoother.

Both sections contain tubules (small tubes), but the cortex has the glomeruli (filters) and convoluted (twisted, curvy) tubules and blood vessels which gives it a grainy appearance. The tubules of the medulla are straighter and are called the collecting tubules (for urine). The medulla also contains the loops of Henle, or the U-shaped parts of the collecting tubules.

When should I contact my healthcare provider about conditions related to the renal cortex?

If you think you might be having problems with your kidneys, you should contact your healthcare provider. You might experience signs and symptoms that include:

• Changes in your urine (like seeing blood or cloudy urine) or urination habits (like more frequent bathroom trips or pain on urination).
• Dry or itchy skin.
• Fatigue (extreme tiredness).
• High blood pressure (hypertension).
• Muscle cramps.
• Poor appetite or metallic taste of food.
• Stomach pain or vomiting.
• Swelling, especially around your ankles or hands.

If you have certain conditions, your provider might order more regular kidney function tests. These conditions include:

• A family history of kidney disease.
• Diabetes.
• Heart disease.
• High blood pressure.
• Obesity or overweight.
• Regular use of certain medications, such as medicine to control your blood pressure.

A note from Cleveland Clinic

If you want to take care of your kidneys, you can start by taking care of your overall health. This means keeping blood pressure and blood sugar under control, staying hydrated and eating appropriately. It also means getting enough sleep and exercise. If you have changes in urination habits or any type of pain, talk to your healthcare provider about what may be going on and how you can work together toward a solution.