What is Kidney cyst? Size, Symptoms, Cause, and Treatments

Introduction of Kidney Cyst

Cysts as part of kidney-related complications, kidney cysts are round pouches,  formed and filled with fluid inside or outside the kidneys. That can form in one or both kidneys. The kidney cyst can be simple (benign) or complex and vary in size. Simple kidney cysts are non-cancerous and harmless, while complex kidney cysts (which may have solid components) have a higher risk of cancer that leads to further health complications.

In Australia, kidney cyst formation is a common disorder in older adults. According to the National Institute of Health (NIH), the prevalence of kidney cyst formation increases with age, as about 50% of individuals over the age of 50 suffer from renal cysts. 

Simple kidney cysts are non-cancerous cysts and do not show symptoms, while complex cysts are malignant cysts,  and show symptoms including pain, increased blood pressure, infection, haemorrhage and urinating problems. The complex cysts require careful monitoring due to the potential and hazardous risks associated with them. To prevent further complications, it is necessary to diagnose the type of kidney cyst.

What is a Kidney Cyst?

Kidneys as part of the urinary system are two bean-shaped paired organs located at the back of the spine. The renal system filters large amounts of blood and excretes waste products in the form of urine. It also plays an essential role in maintaining fluid and electrolyte balance. 

 For more detailed information about kidney structure and function, you can visit the kidney structure and anatomy page.

The blood is filtered through tiny tubules in the kidneys, which collect newly formed urine. When these tubules are blocked, cysts form. Cysts are small pouches that form on tubules and, when detached, result in kidney cysts. In short, kidney cysts are a type of renal disorder.  And kidney cysts are most commonly seen in the elderly.

Kidney cysts can be simple or complex, depending on their severity and symptoms. People often live with simple kidney cysts without knowing because they are harmless and do not show symptoms. However, complex cyst formation disrupts the normal functioning of kidneys and could be cancerous and life-threatening. The table below highlights the main difference between simple and complex kidney cysts.

Types of Kidney Cysts

• Simple (benign ) Non Cancerous Cysts 

Simple cysts are fluid-filled sacs that usually cause no harm. They are commonly found in older adults and rarely cause symptoms.

• Complex Malignant cysts

Complex malignant cysts have irregular shapes, thicker walls, or calcifications that could indicate cancer. Further assessment is usually required to determine malignancy. Complex kidney cysts are of many types, including

• Polycystic Kidney Disease (PKD): It is a genetic disorder where multiple cysts form in the kidneys, which leads to kidney enlargement and kidney failure over time.

• Multicystic Dysplastic Kidney (MCDK): This is a congenital condition in which one kidney develops cysts and is nonfunctional. The other kidney usually compensates for the loss of function.

• Medullary Cystic Kidney Disease: It is a rare genetic disorder in which cysts develop in the medulla (inner part) of the kidney, leading to progressive kidney failure.

• Renal Abscess: A pus-filled cavity in the kidney that is usually caused by any bacterial infection. It requires medical treatment to prevent complications.

• Von Hippel–Lindau Disease: It is a rare genetic disorder that causes cysts and tumours in multiple organs, including the kidneys, and increases the risk of kidney cancer.

• Multilocular Cystic Renal Cell Carcinoma: A rare type of kidney cancer where tumours form in cystic structures within the kidney. It is generally treated with surgery.

• Nephronophthisis: A genetic disorder that causes scarring of the kidney's nephrons (filtering units) that leads to kidney failure. It is usually developed often in childhood or adolescence.

•  Hereditary GCKD (Glomerulocystic Kidney Disease): A rare genetic disorder where cysts form in the glomeruli (filtering structures of the kidney) that leads to the dysfunction of kidneys.

• Tuberous Sclerosis: A genetic disorder causing benign tumours in various organs, including the kidneys, where multiple cysts may develop.

• Do Not Fit in Simple/Complex Cyst Categories: These are the types of cysts that usually do not fit in any category of simple or complex cysts. They include epithelial cysts and hilar cysts. 

• Epithelial Cyst: These types of cysts are usually lined with epithelial cells, potentially benign or precancerous, and do not fit in the typical classification of simple or complex.

• Hilar Cysts: Cysts that form in the renal hilum (where blood vessels and nerves enter the kidney) are often asymptomatic and not categorised as simple or complex.

Difference Between Simple kidney cyst (benign), Complex Kidney Cyst and Polycystic Kidney Disease(PKD)

Table 01: Difference between simple and complex kidney cysts and polycystic kidney disease(PKD)

What causes kidney cysts to grow?

The exact cause of kidney cyst formation is still not fully understood. Certain genetic and medical conditions lead to the formation of kidney cysts, which occur due to various conditions, including Polycystic Kidney Disease (PKD), a hereditary disorder. 

Patients with chronic kidney disease are prone to kidney cysts. Other conditions, such as dietary changes or environmental exposure, do not impact the formation of kidney cysts. However, the risk factors for developing renal cysts are gender, age, renal dysfunction, and hypertension. 

High blood pressure is a risk factor for renal dysfunction, which leads to the development of renal cysts. Other health conditions that cause kidney cyst formation  include

• Chronic kidney disease
• Von Hippel-Lindau disease
• Medullary cystic kidney disease
• Tuberous sclerosis Complex 
• Autosomal dominant polycystic kidney disease

Size of Kidney Cysts

What Size of Kidney Cyst is Dangerous?

Some people may have several cysts, while others have just one. One or more cysts can occur in one or both kidneys. Cysts are spherical in shape and made with thin fibrous connective tissue lined by flattened epithelium. They are usually filled with clear and watery fluid that comes from glomerular filtrate, transepithelial secretions, or both. 

The size of cysts ranges from small to large size. The small cysts can only be visible through a light microscope, and the large ones can be the size of a tennis ball. The bigger size of cysts becomes a major concern because it disrupts the location of other nearby organs and causes complications. 

The size of simple kidney cysts varies in size, ranging from a few millimetres to centimetres. When the size increases, it becomes concerning and requires close observation and intervention. Complex cysts require proper evaluation regardless of their size due to the potential risk of malignancy.

What Size of Kidney Cyst is Cancerous?

Simple kidney cysts are benign and do not cause any problems. The majority of people can live their whole lives without even knowing they have them. Simple kidney cysts are noncancerous and usually do not require any treatment until they show symptoms. 

Complex cysts are more likely to develop cancer than simple cysts, but not all complex cysts are cancerous. Depending on the type of Bosniak classification of the complex cyst, they are at an increased risk of cancer (malignancy). 

Symptoms and Diagnosis 

1. Renal cyst symptoms 

Simple kidney cysts don't affect the functioning of the kidney until they block the ureter from which urine is excreted. There is a slight disruption in kidney functioning due to blocked ureters. There are no such noticeable symptoms in simple cysts because they are mostly discovered incidentally during imaging tests. Slight symptoms of a simple cyst include

• Dull pain in the abdomen or back
• Fever due to infection
• Disruption in urine flow as it blocks the urinary tract

Simple kidney cysts are usually asymptomatic and do not require treatment.  However, complex kidney cysts show the following symptoms depending on their characteristics and require proper management and treatment.

1. Blood in the urine (if the cyst bursts)
2. Stomach or back pain
3. High-grade fever (due to infection)
4. Increased blood pressure (if cysts compress the kidney)
5. Difficulty in urination (if cyst blocks the ureter)

1. How are kidney cysts diagnosed?

Proper diagnosis of the kidney cyst, whether simple or complex, is necessary. It directly impacts treatment, management, and patient outcomes. Simple kidney cysts are not fatal and do not require treatment, but complex cysts need proper management. 

How are kidney cysts detected during routine health exams?

Simple kidney cysts are usually diagnosed incidentally with an imaging test performed for another reason. Kidney cysts can also be diagnosed through ultrasound, and the diagnosis of simple cysts shows a lower chance of cancer. These types of cysts do not require further investigation, follow-up, or treatment; however, medications will be prescribed according to symptoms. 

Complex renal cysts are usually diagnosed with a CT scan.  Complex cysts are hazardous and may cause cancer. After diagnosis, it needs to be treated or removed timely. It can also be diagnosed with

• Medical History
• Kidney ultrasound
• Kidney CT scan (for a detailed picture of the cyst)
• Kidney MRI (for the severity of the cyst)

Bosniak Classification of Kidney Cysts

The CT Scan report shows Bosniak's classification of kidney cysts on the report to assess the risk of cancer and treatment options. The summary of the Bosniak classification system on CT scan shows:

Table 02: Bosniak Classification of Kidney Cysts

Treatment and Management

How to Treat Kidney Cysts?

Medical Treatments

The medical treatment of cysts depends on their type to determine whether they are cancerous or not. Ultrasound is performed to diagnose the type of renal cyst. Simple cysts usually do not require treatment due to the absence of symptoms, but regular ultrasound is still required to observe the changes and signs of simple cysts. 

If cysts are causing symptoms and complications, it is usually diagnosed with a complex cyst. The treatment of complex cysts kidney disease includes

• Dialysis for cleaning of blood
• Kidney transplant in kidney failure case
• Medications and lifestyle changes.

Doctors usually treat simple cysts if they cause symptoms like fever, pain, or urinary blockage. Some studies also showed that draining or removing simple cysts increases blood pressure, but the cause is unknown. 

What treatments are available for kidney cysts removal?

The treatment for kidney cysts involves drainage, sclerotherapy, and surgery.

Drainage: This method drains and removes fluid from the cyst. A thin needle is used to drain to relieve symptoms by reducing the size of the kidney cyst. 

Sclerotherapy: In sclerotherapy, doctors insert a long needle through the skin into the cyst to drain the fluid and inject an alcohol solution.  The process involves injecting an alcohol solution to prevent further fluid filling in the cyst. The procedure is performed with ultrasound as a guide, and the patient is given local anaesthesia.

Is surgery necessary for kidney cysts?

Surgery:  Surgical treatment is performed in cases of large cysts when no other treatment option is left. Surgeons perform laparoscopic surgery to drain the cyst and remove or burn the outer tissue of the cyst. The patient is required to stay in the hospital for 1 or 2 days, and general anaesthesia is used for this procedure. 

Are there natural remedies for kidney cysts?

Drinking more water, consuming less protein, and avoiding smoking can help treat kidney cysts more effectively. However, limited research exists on remedies for kidney cysts, and more conclusive evidence is required to determine their potential benefits.

Preventive Measures

Can simple kidney cysts be prevented?

Kidney cysts can not be prevented, but one can reduce the risk by

• Increased intake of water.
• Decreased intake of sodium
• Managing other diseases like diabetes and hypertension
  

What Foods to Avoid if You Have Kidney Cysts

For kidney disease patients, foods containing sodium, potassium, and phosphorus should be restricted to prevent further complications. These include sugary drinks, colas, brown rice, bananas, processed meat, and dried fruits. These foods are restricted because they cause further complications.

Foods to Consume For Improved Kidney Health

These foods are recommended and should be consumed for better kidney health. It is also helpful in managing kidney cyst symptoms and complications.

• Increased water intake: It helps to flush toxins to excrete out in the form of urine.
• Eat fresh fruits and vegetables: This promotes kidney health and is essential for obtaining nutrients.
• Limit protein intake:  It reduces kidney workload.
• Choose healthy fats: Consume olive oil. Omega 3, omega 6 and fish.

Complications and Risks

Simple kidney cysts do not cause long-term problems or complications, but complex cysts cause many complications. If not treated on time, kidney cysts lead to

• Infection: The infected cyst causes pain, fever, or other symptoms.
• Urine Blockage: The large cyst interrupts and blocks urine flow. It causes kidney damage and infections.
• Burst cyst: The cyst can burst and result in severe pain, blood in the urine and other symptoms.
• Bleeding Cyst: Bleeding inside the cyst breaks and opens the cyst and causes bleeding around the kidney.

Other common complications of  cystic kidney diseases also include:

• Kidney failure.
• Heart valve problems 
• Liver and pancreatic cysts (more common in PKD).
• Growth and development problems among infants.

Are Kidney Cysts Cancerous?

The simple kinds of cysts are not dangerous and are not associated with cancer, while the complex cysts increase the chances of getting kidney cancer. The causes are the size of the renal cysts, the thickness of the wall, and the calcification, which is related to renal cell carcinoma.

Simple cysts are not cancerous and have thin walls filled with clear fluid. They are non-cancerous and have thin walls, while complex cysts are cancerous and have thick, irregular walls inside. The presence of malignant features in the complex type requires immediate treatment.

Such cysts require frequent follow-up, often involving imaging and ultrasound or CT scans to look for changes in size and characteristics leading to malignancy. This includes prevention and early treatment to identify any risks associated with renal cysts.

Are Kidney Cysts Serious?

Kidney cysts can be serious, depending on the type of cyst. Simple cysts do not show signs since the walls of simple cysts are thin and are not malignant. They do not lead to complications but often require medical interventions. Complex cysts are malignant and have thick walls. Kidney cysts can be severe and result in infection and haemorrhage, also responsible for renal failure.

Simple cysts are benign and usually do not need treatment; however, complex cysts require proper management, imaging methods, and biopsies to avoid further problems.

Can Kidney Cysts Burst?

Kidney cysts usually remain stable, but they may rupture in certain conditions. Large kidney cysts are likely to rupture by trauma or significant pressure. A burst cyst shows symptoms like severe back and side pain, blood in the urine, and fever due to infection. When a kidney cyst bursts, it can lead to complications such as infection, bleeding, or impaired kidney function.

It is essential to manage the underlying condition as the burst cyst requires immediate treatment and medical attention to manage the condition and complications. Treatment often involves hospitalisation, where doctors may administer antibiotics to prevent or treat infections, control bleeding, and monitor kidney function. 

In severe cases, a surgical procedure to drain the cyst or repair damage will be recommended. Effective management of kidney cyst rupture involves addressing the root causes and preventing further harm to the kidneys.

Specific Types and Conditions

Kidney cysts are small sacs filled with fluid that can develop in the kidneys or on their outer surface. Most kidney cysts are benign and asymptomatic, but a few types and conditions can cause cancer, especially complex and hemorrhagic renal cysts.

Are Complex Kidney Cysts Cancerous?

Compared to simple cysts, complex kidney cysts are different in shape, wall thickness, and calcification. These characteristics make them worse because complex cysts are more prone to have cancerous features. However, it is essential to understand that not all complex cysts are malignant. 

The Bosniak classification system is used to evaluate the risk of malignancy in complex kidney cysts. The higher number of classifications is linked with increased cancer risk. Imagining tests, MRI, and biopsy are performed to determine whether the complex cyst is cancerous or not.

What Are The Risks Of Hemorrhagic Kidney Cysts?

Hemorrhagic kidney cysts result when a blood vessel within a kidney cyst bursts, and the cyst is filled with blood. It shows symptoms, including pain, discomfort, or hematuria(blood in the urine). 

Hemorrhagic cysts are not usually cancerous but cause complications in severe and repeated bleeding. These cysts are usually harmless and disappear over time. However, if not treated, it also causes discomfort or recurrent appearance of symptoms.

Kidney Cysts in Specific Populations

Pediatric Kidney Health

Kidney cysts in children are usually caused by a congenital condition known as Polycystic kidney disease (PKD), but they may also be caused by congenital side effects during birth. Children with kidney cysts require careful evaluation and proper treatment on time. The management depends on the cause, medication, or surgery to prevent any further complications of the kidney.

Geriatric Kidney Health

Due to the ageing process, older adults are more likely to develop kidney cysts. Although most cysts in this population are benign and asymptomatic, multiple or large cysts contribute to progressive kidney damage.  

In some cases, genetic factors also play a role, such as in polycystic kidney disease (PKD), where inherited mutations lead to the development of multiple cysts, which increases the risk of kidney dysfunction. 

Depending on the size and location of these cysts, the geriatric patient requires regular checkups to ensure that they do not cause serious complications, such as impaired kidney function or infection. Early detection and monitoring are essential for managing these risks effectively.

Frequently Asked Questions  

Can Liver and Kidney Cysts Cause Pain?

Liver and kidney cysts cause discomfort and pain but do not show symptoms. The increased size of these cysts causes symptoms to appear. Although not all cysts are malignant in nature, changes in size disrupt the other functioning of organs, resulting in discomfort and pain. 

The pain may arise from the side, back, or upper abdomen. However, the pain in the upper right quadrant of the abdomen indicates a liver cyst. Besides pain, other symptoms include a feeling of fullness, bloating, or tenderness in the abdominal area. However, if a cyst is filled with clear fluid, a person can experience severe pain in case of infected cyst or cyst bursts.

Are Kidney Cysts Hereditary?

Kidney cysts can be hereditary based on the type of renal cyst. Polycystic kidney disease (PKD) is one of the most common hereditary diseases characterised by the presence of cysts in the kidneys. PKD is the formation of multiple cysts in the kidneys, resulting in various complications. 

This condition often occurs in an autosomal dominant manner and increases the chances of offspring developing the disease by 50% if one parent is affected. There is also a rare form called autosomal recessive polycystic kidney disease, in which both parents carry the gene for the child to be affected. Simple renal cysts are a more common form of renal cysts, are not hereditary and develop occasionally with individuals’ age.

Can Kidney Cysts Cause High Blood Pressure?

Kidney cysts are linked to increased blood pressure, mainly in polycystic kidney patients (PKD). PKD is characterised by the presence of various cysts that disrupt the normal functioning of the kidney and raise high blood pressure. 

This is because the kidneys are involved in managing blood pressure by controlling the fluid amount and maintaining electrolytes in the body. If cysts interfere with their functioning, it leads to hypertension, one of the complications of PKD. Blood pressure regulation is important in patients with kidney cysts to avoid worsening the condition and cardiovascular disease. 

Can lifestyle changes prevent the growth of kidney cysts?

Lifestyle changes alone cannot completely prevent kidney cysts from growing. However, maintaining a healthy diet, staying hydrated, managing blood pressure, and avoiding smoking helps support overall kidney health and reduces the risk of complications.

What complications can arise from untreated kidney cysts?

Untreated kidney cysts can lead to complications like kidney infection, bleeding, or the cyst bursting. In some cases, they can also cause kidney function to decline, which can lead to more serious kidney problems over time.

How are large renal cysts treated?

Large renal cysts that cause pain, infection, or other issues are typically treated through drainage or surgery. A doctor may use a needle to drain the cyst or perform surgery to remove it if needed. In some cases, medication may be used to manage symptoms or prevent infection.