Kidney Cysts: Should You Be Concerned?

Overview

Finding out that you have a growth on or in your kidneys, or a cyst to be specific, can be unsettling. However, kidney cysts are extremely common, and it is important to monitor them to ensure they do not cause complications. Most kidney cysts are not harmful, but they need regular monitoring to ensure they remain so. These growths may need treatment depending on their size and type. Understanding kidney cyst symptoms, types, and classification can help you make sense of the diagnosis and know when to act, if at all.

What Is a Kidney Cyst?

Formed in or on the kidneys, kidney cysts are simply fluid-filled pouches with thin walls that are more common as you get older. While renal cysts or  “growths” may sound concerning, they are actually some of the most common incidental findings in abdominal imaging and are usually nothing to worry about.

These cysts vary in size and are usually less than 2 inches wide. They may either stay the same size or grow with time. It is possible for a person to have more than one cyst, and these growths can be found in one or both kidneys at the same time. Generally, there are two primary types of kidney cysts: simple and complex.

Simple vs Complex Cysts

Simple Kidney Cysts: If you have a simple kidney cyst, there is a good chance you may not even feel it. These cysts usually do not cause specific symptoms and are benign in most cases. In terms of their structure, they are small, round, fluid-filled sacs with thin walls. Simple kidney cysts do not require any treatment, nor do they have a negative impact on your life. 

Complex Kidney Cysts: On the other hand, complex renal cysts may have malignant potential. Contrary to simple cysts, these can be solid, irregularly shaped, and may have a thick outer wall. While a simple kidney cyst is classified as category I, complex cysts can be either II, II-F, III, or IV. As the cyst grows, the risk of it becoming cancerous increases. 

For example, category II usually does not require monitoring, but II-F has a 5% chance of becoming malignant. Similarly, category III has a 50-80% risk of malignancy in the body, while category IV can go up to 90%.

Comparing Types of Kidney Cysts 

According to the Bosniak Classification System (2019 revision), renal cysts are classified into five categories: I, II, II-F, III, and IV. [Ref]

 

Symptoms of Renal Cysts

While most renal cysts do not produce any symptoms at all, larger cysts may do so. These cysts can be as large as 4-5 cm. Kidney cyst symptoms include:

• Pain or dull ache in your side, typically the region between your hips and ribs. 

• Stomach or back pain.

• Frequent urination.

• Dark-coloured urine.

• Hematuria: Presence of blood in the urine.

• Fever

• Hypertension

In some cases, renal cysts can also cause high blood pressure if they disrupt the kidneys' ability to filter excess fluid from the blood. It is important to distinguish these from kidney cyst symptoms, such as weight loss, fatigue, or a palpable abdominal lump. 

Moreover, sudden and sharp abdominal pain could indicate a ruptured or haemorrhaging cyst, which would need immediate medical attention. 

How Are Kidney Cysts Caused?

Kidney cysts develop when the tubules within the nephron swell and fill with fluid. Although the exact cause remains unknown, it is believed that their formation could be influenced by multiple factors. Sometimes, an injury or small blockages in the tubes can result in simple kidney cysts. 

People above the age of 50 are more prone to developing kidney cysts. Other risk factors include:

• Chronic Kidney Disease (CKD)

• Von Hippel-Lindau disease

• Tuberous Sclerosis Disease

• Polycystic kidney disease

Renal Cyst Diagnosis: How Are They Found?

Renal cyst diagnosis is made almost exclusively through kidney imaging. In the majority of cases, these cysts show up by accident while medical professionals conduct imaging tests for a completely unrelated condition. Once a cyst is recognised, other tests can be recommended, including:

• Ultrasound: Doctors can create images of your kidneys using high-frequency sound waves and echoes.

• Magnetic Resonance Imaging: Images are created using magnets, radio waves, and computer processing. MRIs are the best way to classify a kidney cyst, as they help distinguish between fluid-filled and solid growths. 

• Computed tomography: Through a CT scan, doctors produce 3D images of the kidneys.

• Kidney function test: Blood and/or urine tests are performed to determine whether the cysts are affecting kidney function. 

Treating a Kidney Cyst

Kidney cysts only need to be treated if they are posing a threat to your health. In case of simple cysts, you may not need to worry about having them removed at all. However, if the cyst is pressing on another organ, harming the kidneys, or there is a chance that it could turn cancerous, they can be treated by one of the following ways:

• Surgery: Laparoscopic surgeries are used to remove a cyst from the kidneys, in which doctors insert a thin instrument into the body through small incisions in the abdomen. The cyst is drained before it is removed. Surgeons may also burn the outer tissue of the cyst.

• Aspiration and Sclerotherapy: Here, a needle is inserted through the skin to puncture and drain the cyst. A special solution may be injected to prevent the fluid from collecting again. 

How NU Hospitals Can Help 

NU Hospitals, Bangalore, is one of the most specialised kidney care hospitals in India, with over 750 kidney transplants and 60,000+ surgeries done to date. As far as the evaluation of renal cysts is concerned, NU Hospitals offers its patients the best imaging technology, including CT, MRI, and ultrasound, to make an accurate diagnosis. Our team of nephrologists and urologists ensures that patients leave the hospital not only with the best solution to their problem but also with peace of mind, with their kidney function in mind.  

Finding a cyst on one of the most vital organs of your body may be concerning, but it is usually manageable. By understanding the distinction between simple and complex cysts and staying consistent with the recommended kidney imaging, you can ensure long-term renal health.