Renal Sinus

What is the renal sinus?

The renal sinus is a central part of your kidney where things go in (like nerves and arteries) and come out (like pee, veins and lymphatic channels). Like the rest of your kidney, the renal sinus has fat padding around it. It contains:

• Body fat.
• Autonomic nerves, which control involuntary actions.
• Connective tissue.
• Lymphatic channels.
• Major and minor calyces, where urine collection starts.
• Renal artery and vein.
• Renal pelvis, which collects urine as it’s produced.

Most of your renal sinus is fat that wraps around the other structures. The amount of fat in a kidney’s renal sinus gradually increases with age and weight gain.

What is the main function of the renal sinus?

The renal sinus is part of your kidney anatomy. It acts as a compartment containing fat and other kidney parts. It’s the area where things go in and come out, with fat padding for protection.

Where is the renal sinus located?

The renal sinus is in the middle part of the kidney.

What color is the renal sinus?

The renal sinus is padded with mostly fat, and fat often appears white or yellow.

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

Conditions and disorders affecting the renal sinus include:

• Renal sinus cyst: A noncancerous, fluid-filled sac that starts growing either outside the renal sinus (parapelvic cyst) or inside the renal sinus (peripelvic cyst).
• Renal sinus lipomatosis: A condition that occurs when there is too much fat in the renal sinus.
• Benign multilocular cystic nephroma: A noncancerous tumor that can grow into the renal sinus.

Other conditions may affect the parts found within the renal sinus, such as the calyces. These conditions include:

• Caliectasis: Your calyces (where urine collection begins) become swollen with excess fluid. Caliectasis may result in kidney failure if not treated.
• Vascular lesions: Also called renal artery aneurysm, arteriovenous communication or renal vein varix, this is when a bulge forms in the wall of a renal artery inside the renal sinus.
• Renal cell carcinoma: A cancerous tumor that can grow into the renal sinus.

Some studies have found that the amount of fat inside the renal sinus, which changes with age and weight, can affect blood pressure.

What tests are used to examine the renal sinus?

Imaging tests can show kidney abnormalities or growths. The most common types of imaging used to examine the kidneys include:

• CT scan.
• MRI.
• Kidney ultrasound.
• Nuclear imaging.

Other types of tests used to check the health of your kidneys include:

• Blood tests to show how well the glomeruli inside of your kidney filter blood.
• Kidney biopsy.
• Ureteroscopy.
• Urinalysis.

How common are renal sinus cysts?

Both lipomatosis and cysts are common types of renal sinus lesions that occur as people grow older. About 33% of people over age 70 have at least one renal cyst occurring in or outside of the renal sinus.

Simple renal cysts usually don’t cause symptoms, so you often don’t know you have them. Providers usually diagnose them when you have an imaging exam for other health reasons.

How do I know if I have a renal sinus cyst?

Most of the time, renal sinus cysts are asymptomatic (don’t cause symptoms). If they do cause symptoms, you may notice:

• Pain in your side between your ribs and hip, stomach or back.
• Fever.
• Having to go to the bathroom more than usual (frequent urination).
• Blood in your urine or dark urine.

What are the most common treatments for renal sinus cysts?

In most cases, a renal sinus cyst doesn’t cause any symptoms. Your provider may want to monitor it closely with regular checkups or imaging tests. If the cyst ruptures, bleeds, becomes infected or grows too large, it may cause complications. Although rare, your provider may recommend surgery to remove the renal sinus cyst.

How do I keep my renal sinus healthy?

The best way to keep your renal sinus healthy and avoid complications is to maintain a healthy weight. Gaining weight can increase renal sinus fat.

Other ways to lower your risk of developing kidney problems:

• Quit smoking.
• Avoid excess salt in your diet, which impacts the balance of minerals in your blood.
• Stay hydrated with plenty of water to help your kidneys flush out toxins.
• Exercise every day, which helps control blood pressure.
• Reduce your use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, which damage the kidneys if overused.
• Keep an eye on your blood pressure levels.
• Monitor your blood sugar levels if you have diabetes.

A note from Cleveland Clinic

The renal sinus is a compartment inside your kidney that uses fat to cushion important parts like the renal pelvis, lymphatic channels, calyces and renal artery. The most common disorder associated with the renal sinus is a renal sinus cyst, which is usually asymptomatic and harmless. If you notice any symptoms like pain, frequent urination or blood in your urine, see your healthcare provider.