Renal Cortex

The renal cortex (or kidney cortex) is the outer layer of the kidney. The cortex surrounds the inside of the organ, the medulla. The renal cortex has a covering, the renal capsule, which is a layer of tougher protective tissue.

The cortex of your kidney is where the nephrons (blood-filtering units) begin. Each kidney has 1 million nephrons. The filtering unit of the nephron is the glomerulus. This attaches to a small tube (tubule) that removes waste and returns the needed substances to your body. In the renal cortex, the tubules are twisted. In the medulla, the tubules are straighter.

What is the function of the renal cortex?

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

• The balance of electrolytes and water
• Your body’s blood pressure and the amount of fluid outside your cells
• Red blood cell production
• The balance between acids and bases
• Vitamin D production
• The balance between calcium and phosphorus
• Production of some glucose (sugar) besides what your liver makes

Where is it located?

The renal cortex is the outer part of your kidney, which is part of the urinary tract. Your kidneys are just below your rib cage and toward your back. Typically, one kidney sits on either side of your spine. The kidneys are between your intestines and your diaphragm. A tubelike structure called a ureter connects each kidney to your bladder.

What are the parts of a renal cortex?

Your kidney cortex has capillaries (tiny blood vessels) and tubules close together. These renal tubules come out of renal corpuscles, where filtration happens in blood vessels.

What does it look like?

The renal cortex is red and is the outside part of your kidney. It covers the renal medulla, the inside part of your kidney. The medulla contains little triangular structures called the renal pyramids. The renal cortex goes over and between the renal pyramids.

Your kidney is about as big as your fist.

What are the common diseases of the renal cortex?

Many different disorders can affect your kidneys, including:

• Chronic kidney disease (CKD)
• Kidney cancer
• Kidney failure
• Kidney infection
• Kidney stones
• Kidney cysts
• Polycystic kidney disease (PKD)

Many other disorders can affect or be related to your kidneys. Some of these conditions include:

• Metabolic acidosis (acid buildup)
• Nephritis (inflammation)
• Diabetes-related nephropathy
• Glomerular diseases
• Proteinuria (high levels of protein in your urine)
• Uremia (waste buildup in your blood)

Signs or symptoms that something isn’t working right

Most kidney problems don’t have symptoms in the early stages. Most of the time, pain in your lower back isn’t kidney pain. As kidney damage progresses, you may notice:

• Cramping muscles: Electrolyte imbalances can cause your muscles (usually in your calf) to stiffen.
• Dark or bloody urine: 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 swelling.
• Sleep problems, fatigue and lack of appetite: If toxins build up in your blood, your sleep, appetite and energy levels may be off.

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

• Imaging tests (X-ray, CT scan, MRI, ultrasound or nuclear medicine): These can show kidney blockages or issues like renal cortical thinning. This may mean your kidney isn’t working well.
• Kidney biopsy: In this test, your provider removes a small amount of kidney tissue to examine under a microscope.
• Ureteroscopy: Your provider passes a tube with a small camera (endoscope) through your urethra into your bladder and ureters to look for anything unusual.
• Urinalysis: This measures certain substances, like protein or blood, in urine to detect a disease or infection.
• Kidney function tests: These tests show how well your kidneys are working to clear waste from your blood.

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. This is especially valuable 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
• Drinking enough water to clear out toxins
• Increasing daily physical activity to reduce high blood pressure
• Limiting your use of nonsteroidal anti-inflammatory drugs
• Maintaining a weight that’s healthy for you
• Checking your blood pressure regularly
• Watching your blood sugar levels to manage diabetes

When should I contact my healthcare provider?

Contact your healthcare provider if you’re having signs and symptoms like:

• Urine changes or changes in how often you pee
• Dry or itchy skin
• Fatigue
• High blood pressure
• Muscle cramps
• Poor appetite or metallic-tasting food
• Stomach pain or vomiting
• Swelling, especially around your ankles or hands

Your provider might order more regular kidney function tests if you have a biological family history of kidney disease or take certain medicines. They may also order tests if you have conditions like:

• Diabetes
• Heart disease
• High blood pressure
• Obesity or overweight