01-10-2024 11:03 AM

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

Introduction of Kidney Cyst

Cysts are fluid sacs filled with water that form on the kidney. They are round and can form both inside and outside the kidney. Depending on the size, cysts can be simple or complex.

Simple kidney cysts are harmless and non-cancerous. But complex kidney cysts (which may have solid components) have a high risk of cancer. As a result, they further lead to health complications.

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

Simple kidney cysts do not show symptoms and are non-cancerous. But complex cysts are malignant and show symptoms. These symptoms include pain, increased blood pressure, infection and urinating problems.

Complex cysts need careful monitoring due to the potential hazardous risks. It is necessary to diagnose the type of cyst to prevent further complications.

What is a Kidney Cyst?

Kidneys are two bean-shaped paired organs located at the back of the spine. They are part of the urinary system. The kidneys filter the blood to excrete the waste products in the form of urine. They also play an important role in maintaining fluid and electrolyte balance.

For more details about kidney structure and function, 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 they are most commonly seen in the elderly.

Kidney cysts can be simple or complex, depending on their severity and symptoms. People live with simple kidney cysts without knowing about them. Because they are harmless and do not show any symptoms. But complex cysts are cancerous and life-threatening. They disrupt the normal functioning of the kidneys. 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. They 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. It 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. It leads to progressive kidney failure.

Renal Abscess:

A pus-filled cavity in the kidney is usually caused by a bacterial infection. It requires medical treatment to prevent complications.

Von Hippel–Lindau Disease:

It is a rare genetic disorder. It causes cysts and tumours in multiple organs, including the kidneys. This type 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 kidneys' nephrons (filtering units) that leads to kidney failure. It is usually developed in childhood or adolescence.

Hereditary GCKD (Glomerulocystic Kidney Disease):

It is a rare genetic disorder. These cysts form in the glomeruli (filtering structures of the kidney). These cysts lead to the dysfunction of the 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 into 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. They do not fit into 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. They are not categorised as simple or complex.

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

Aspect	Simple Kidney Cysts (Benign)	Complex Kidney Cysts	Polycystic Kidney Disease (PKD)
Definition	Fluid-filled sacs that form in the kidneys, usually benign and non-cancerous.	Cysts with irregularities, such as septa, calcifications, or solid components, potentially indicate malignancy.	A genetic disorder where clusters of cysts form in the kidneys, leading to enlarged kidneys and impaired function over time.
Causes	Mostly idiopathic (unknown cause); may develop with ageing.	Arise from underlying conditions like PKD or chronic kidney disease.	Caused by inherited mutations in specific genes (PKD1, PKD2) resulting in cyst development and kidney dysfunction.
Risk of Cancer	Non-cancerous, rarely linked with malignancy.	Higher risk; the complexity of the cyst increases malignancy.	Typically non-cancerous, but the disease leads to serious complications like kidney failure.
Appearance	Typically round or oval with smooth, thin walls filled with clear fluid.	Irregular shape, thickened or irregular walls, presence of septa, calcifications, or solid components.	Multiple cysts of varying sizes in both kidneys, leading to enlarged kidneys. Cysts can appear in other organs as well, such as the liver.
Symptoms	Mostly asymptomatic, causing discomfort or pain if large.	Depending on size and complexity, it causes pain, blood in urine, and infection.	Symptoms include high blood pressure, back or side pain, headaches, blood in urine, frequent kidney infections, and progressive loss of kidney function.
Diagnosis	Can be detected through ultrasound, CT scan.	Requires more detailed imaging (e.g., enhanced CT, MRI) to assess malignancy risk.	Diagnosed through ultrasound, CT scan, or MRI; genetic testing may also be used, especially if there is a family history of PKD.
Treatment	No treatment is required unless symptomatic.	Require monitoring, aspiration, or surgical intervention depending on the risk of malignancy and symptoms.	No cure, but treatment focuses on managing symptoms: blood pressure control, pain management, and treatment of infections. In advanced stages, dialysis or kidney transplant may be necessary.
Follow-up	No follow-up if asymptomatic and benign.	Regular follow-up imaging to monitor changes in the cyst's characteristics.	Regular monitoring of kidney function and blood pressure, frequent imaging to track cyst growth and potential complications, and genetic counselling for family planning are also advised.

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. But genetics and medical conditions lead to kidney cysts. They occur due to various conditions, including polycystic kidney disease. Well, PKD is a hereditary disorder.

Patients with chronic kidney disease are prone to kidney cysts. Dietary changes or environmental exposure do not impact the formation of kidney cysts. However, age, gender, renal dysfunction and hypertension are the risk factors.

High blood pressure also causes 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. They are made with thin fibrous connective tissue lined by flattened epithelium. Cysts are usually filled with clear and watery fluid. This fluid comes from glomerular filtrate, transepithelial secretions, or both.

The cysts' sizes range from small to large. It ranges from a few millimetres to centimetres. The small cysts can only be visible through a light microscope, and the large ones can be the size of a tennis ball. When the size increases, it becomes concerning and requires close observation and intervention. The larger size of cysts becomes a major concern. Because it disrupts the location of other nearby organs and causes complications.

Smaller cysts under 3 cm are usually harmless. They are discovered incidentally in imaging tests that are performed for other conditions. They do not cause any symptoms.
Medium-sized cysts of 3-5 cm may cause symptoms such as discomfort or pain in the abdominal region. They are also harmless until they become infected or grow in size.
Large cysts that are greater than 5cm are dangerous and cause complications.

However, complex cysts, regardless of their size or shape, are more dangerous due to the higher risk of malignancies. These types of cysts need proper evaluation.

What Size of Kidney Cyst is Cancerous?

Simple kidney cysts are benign, non-cancerous and do not cause any problems. The majority of people can live their whole lives without even knowing they have them. Simple cysts usually do not need 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

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 noticeable symptoms in simple cysts. However, 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. But they show the following symptoms depending on their characteristics. However, they require proper management and treatment.

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

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. For example, during an imaging test that is mostly performed for other reasons. Kidney cysts can also be diagnosed through ultrasound.

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)

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Bosniak Classification of Kidney Cysts

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

Classes	Risk of cancer	Risk of Cancer and Treatment Option
Bosniak 1 cyst	Risk of cancer <1%	Benign and does not require follow-up
Bosniak 2 cyst	Risk of cancer <5%	Benign and does not require follow-up
Bosniak 2F cyst	Risk of cancer: 5%	Low risk of cancer and requires follow-up imaging to assess progress
Bosniak 3 cyst	Risk of cancer 50%	Intermediate risk of cancer and should be surgically removed or closely monitored
Bosniak 4 cyst	Risk of cancer 80-95%	Higher risk of cancer and should be surgically removed

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. Whether they could be 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. Regular ultrasound is a must to observe the changes and signs of simple cysts.

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

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

Doctors usually treat simple cysts. Especially if the symptoms are 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. By inserting the needle, they 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. The patient is given local anaesthesia during the process.

Is surgery necessary for kidney cysts?

Surgery:

Surgical treatment is performed in cases of large cysts. Especially 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 are the natural remedies. But limited research exists on remedies for kidney cysts. However, more conclusive evidence is needed 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

Kidney disease patients must avoid foods containing sodium, potassium, and phosphorus. These include sugary drinks, colas, brown rice, bananas, processed meat, and dried fruits. These foods are restricted because they cause further complications.

Restricted Foods	Further Complications
Sugary Foods and Drinks(sodas and pastries)	Consumption leads to insulin resistance and cyst growth
High-sodium food (processed foods and salty snacks)	Increases blood pressure and strain kidneys
High-protein food (red and processed meat)	Burden kidneys and worsen cyst conditions
Oxalate-rich foods (spinach, dry fruit, and nuts)	Contribute to kidney stone formation
Caffeinated beverages (coffee, energy drink, sports drink)	Stimulate cyst growth and causes dehydration
Phosphorus-rich foods (dairy and processed meat)	Results calcification in kidneys

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 them 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. 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. It relates 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.

Complex cysts are cancerous and have thick, irregular walls inside. The presence of malignant features in the complex type requires immediate treatment.

Such cysts need frequent follow-up. Imaging and ultrasound or CT scans 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. They are also responsible for renal failure.

Simple cysts are benign and usually do not need treatment. However, complex cysts need 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 due to 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. Often results in bleeding or impaired kidney function.

It is essential to manage the underlying condition. The burst cyst requires immediate treatment and medical attention to manage the complications. Treatment often involves hospitalisation. Doctors 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 to prevent further harm.

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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. For example, complex and haemorrhagic renal cysts.

Are Complex Kidney Cysts Cancerous?

Complex kidney cysts are different in shape, wall thickness, and calcification. These characteristics make them worse. Because complex cysts are more prone to having 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. 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 Haemorrhagic Kidney Cysts?

Haemorrhagic 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 haematuria (blood in the urine).

Haemorrhagic cysts are not usually cancerous. But they 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 the recurrent appearance of symptoms.

Kidney Cysts in Specific Populations

Pediatric Kidney Health

Kidney cysts in children are usually caused by a congenital condition. They are also 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 further complications.

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. But in most cases, multiple or large cysts contribute to progressive kidney damage.

Genetic factors also play a role, such as in polycystic kidney disease (PKD). It is inherited mutations that lead to the development of multiple cysts. It also increases the risk of kidney dysfunction.

The geriatric patient requires regular checkups. The checkup is important 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. However, changes in size disrupt the functioning of the organ. They also result 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.

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.

PKD is the formation of multiple cysts in the kidneys, resulting in various complications.

This condition often occurs in an autosomal dominant manner. It 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 this disease, both parents carry the gene for the child to be affected.

Simple renal cysts are a more common form of renal cysts. They 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 disease (PKD). PKD is characterised by the presence of various cysts. It disrupts the normal functioning of the kidney and raises blood pressure.

Kidneys manage blood pressure by controlling the fluid amount and 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. Controlled blood pressure helps 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. It 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.