Cortical Thinning Of The Kidneys In Chronic Kidney Disease

The human body has two kidneys, which play an important role in your health. When they function correctly, they filter out waste products from the blood and keep it clean. This is a process called glomerular filtration.

The kidneys also help control blood pressure and red blood cell production and produce vitamins that aid growth and keep the bones healthy.¹

Chronic kidney disease (CKD) affects 37 million adults in the US. Characterized by the gradual loss of kidney function over time, CKD may lead to cortical thinning of the kidney.² ³

What is cortical thinning of the kidney?

The kidneys contain millions of nephrons which contain a glomerulus and a tubule. Nephrons act like mini blood filters.⁴

The kidney has two main parts: the renal cortex and the renal medulla.

The renal cortex is the outer part of your kidney, which contains blood vessels connected to nephrons. This is where blood is filtered. The renal medulla contains renal pyramids, triangular structures that contain nephrons. This part of the kidney controls urine concentration and regulates water and salts in the blood.⁵

When the kidney cortex becomes scarred and the amount of healthy, functioning tissue decreases, you may have cortical thinning. This can occur for many reasons.⁶

What causes cortical thinning of the kidney?

The kidney cortex could become thinner for the following reasons:

Nephron loss caused by CKD

Cortical thinning of the kidney can occur due to a reduction in the number of nephrons and declining kidney function. Chronic kidney disease can lead to these effects.⁷

Ischaemic nephropathy is a type of kidney disease caused by reduced blood flow to the kidney. The condition can reduce the size of the kidneys.⁸

You may be at increased risk of ischaemic nephropathy as you get older or if you have high blood pressure, diabetes, or renovascular disease (RVD). In RVD, the arteries supplying blood to the kidneys are narrowed.

CKD can also occur due to autoimmune diseases like lupus nephritis and inherited conditions like polycystic kidney disease (PKD).

In addition to reduced kidney size, CKD often leads to cortical thinning.³

Reflux nephropathy

A type of kidney disease called reflux nephropathy can cause cortical thinning of the kidney.⁷

Reflux nephropathy occurs when the kidneys become damaged due to the backward flow of urine from the bladder to the kidneys. Nearly all reflux nephropathy cases are caused by birth defects.⁹

Each ureter has a one-way valve to keep urine in the bladder. However, reflux nephropathy can occur in people whose valves do not function well or whose ureters do not properly attach to the bladder.

Risk factors for reflux nephropathy include:¹⁰

• Ureteral injury

• Congenital hydronephrosis (dilated or enlarged renal pelvis — the part of the kidney where urine is collected — in newborns)

• Repeat urinary tract infections (UTIs)

• Personal or family history of vesicoureteral reflux (VUR) (a condition where urine flows from the bladder back up one or both ureters)

Other conditions that affect the flow of urine may cause reflux nephropathy, including:

• Bladder stones

• Bladder outlet obstruction (BOO) — may be caused by an enlarged prostate in men, pelvic tumors, or urethral stricture (a narrowing of the urethra)

• Neurogenic bladder — this occurs when a person has reduced control of bladder function due to a condition of the brain, nerves, or spinal cord

Age

Research shows cortical thinning is characteristic of aging kidneys.¹¹

Many studies (but not all) have shown that kidney volume decreases with age. One such study involving 1,344 healthy potential kidney donors aged 18 to 75 years found that kidney volume was stable until the age of 50 and began to decline thereafter. The cortex volume was shown to peak in the 30–39 age group, then decline in each subsequent age group.¹¹

Symptoms of cortical thinning

Cortical thinning of the kidney does not necessarily cause direct symptoms, but any symptoms you have may be related to the underlying cause.

Make an appointment to see your doctor if you notice changes in your urine, such as seeing blood or foam, or if you need to urinate more frequently.

General symptoms of late-stage chronic kidney disease include:¹²

• Needing to urinate more, particularly at night

• Blood in your urine (hematuria)

• Shortness of breath

• Fatigue

• Trouble sleeping

• Weight loss

• Reduced appetite

• Nausea

• Headaches

• Swollen hands, feet, or ankles

• Muscle cramps

• Itchy skin

• Erectile dysfunction

Diagnosing cortical thinning of the kidney

Measuring the kidney’s cortical thickness can help detect kidney disease and assess the extent of renal function loss.

Renal cortical thickness can be measured using ultrasound imaging techniques, including scanning the kidneys during a transabdominal ultrasound. This method is simple, non-invasive, and cost-effective.

Your medical team may use other methods to assess your kidney function.

The glomerular filtration rate (GFR) test can show how effectively your kidneys are filtering your blood and removing waste. To get an estimated GFR level (eGFR), you will undergo a blood test. Your doctor will measure the creatinine levels in your blood sample to get an eGFR number.

Normal eGFR levels decline with age, but here is their general meaning:¹³

• 90 or higher: normal range

• 60–89: could suggest you have early-stage kidney disease

• 15–59: could suggest you have kidney disease

• Below 15: could suggest you have kidney failure

If your doctor needs more information about what’s causing your symptoms, they may recommend you undergo a kidney biopsy. This procedure involves having a thin needle inserted through your skin into your kidney to obtain a sample. The sample is then sent to a lab for examination.

Treating cortical thinning of the kidney

Chronic kidney disease and cortical thinning of the kidney have no cure, but it’s possible to slow their progression and relieve your symptoms.¹⁴

The treatment your doctor recommends will depend on the type of kidney disease and how advanced your condition is.

There are four broad categories of CKD treatment: lifestyle adjustments, medication, dialysis, and kidney transplant.¹⁵

Lifestyle adjustments

Changing your lifestyle habits could help you manage your CKD. These include:

• Eating a balanced, healthy diet

• Consuming less salt — you should aim for less than 6g (around one teaspoon) per day

• Limit your alcohol intake

• Losing weight if you are overweight or obese

• Exercising regularly

• Quitting smoking

• Avoiding over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen

Medication

Your doctor can prescribe medication to help treat the conditions that cause CKD, like high blood pressure and diabetes.

Medication can also help manage your CKD complications, such as high blood potassium levels (hyperkalemia) and water retention (edema).

There is no specific medication for CKD itself.

Dialysis

A dialysis is a treatment option for when the kidneys no longer work sufficiently. This may be the case when you have lost 85–90% of your kidney function and your GFR level is below 15.¹⁶

There are two main types of dialysis: hemodialysis and peritoneal dialysis.

Hemodialysis is a process through which blood leaves your body and passes through a machine that removes excess fluid and waste products.

Peritoneal dialysis is where your peritoneal cavity (your abdominal area) is filled with dialysate solution through a catheter. This solution draws waste products from your bloodstream and then leaves the body through the catheter. You can carry out this process independently throughout the day or use a machine while you sleep.

You will need to have dialysis for the rest of your life if your kidneys have failed.

Kidney transplant

A kidney transplant is an effective treatment for some people with end-stage kidney disease. It involves a donated healthy kidney being put into your body.

The donated kidney could come from a living relative (you can live with one healthy kidney) or a deceased donor.

You will need to take immunosuppressants for the rest of your life to ensure your body doesn’t reject your new kidney.

The lowdown

Cortical thinning of the kidney is where the thickness of the renal cortex (the outer part of the kidney) decreases over time, reducing kidney function.

Cortical thinning is thought to occur due to kidney disease, reflux nephropathy, and the normal aging process. There is no specific treatment.

Your doctor may use ultrasound to diagnose cortical thinning. They may recommend lifestyle changes or medication as part of a treatment plan to help tackle the underlying cause and resulting complications. Dialysis or transplant may be the best treatment for people with end-stage kidney disease.

Frequently asked questions

What causes cortical thinning of the kidney?

The kidney cortex can get thinner due to kidney disease. People develop kidney disease due to various reasons, including high blood pressure, diabetes, or inherited conditions.

Reflux nephropathy — a type of kidney damage caused when urine travels backward from the bladder to the kidneys — could also cause cortical thinning.

Cortical thinning is also thought to occur with age.

Can you slow thinning of the kidney cortex?

You can take steps to help keep your kidneys healthy. This involves controlling your weight, exercising regularly, giving up smoking, consuming less alcohol, monitoring your cholesterol, blood sugar, and blood pressure, and consuming a low-salt diet.

Is cortical thinning of the kidney treatable?

You can’t reverse cortical thinning or any other type of kidney damage. However, you can make changes to your lifestyle to keep your kidneys healthy, take medications to treat the causes or complications of kidney damage, undergo dialysis, or have a kidney transplant.