Kidney cyst

Last updated date: 14-Apr-2023

Originally Written in English

Kidney cyst


People with simple kidney cysts have fluid-filled sacs within their kidneys. One or more cysts in one or both kidneys is conceivable. Simple kidney cysts have no known etiology, however they become more prevalent as people age. Renal cysts can be benign or malignant, focal, multifocal, unilateral, or bilateral, and congenital or acquired, with the latter being the more prevalent.


Kidney cyst definition

Kidney cyst definition

A kidney cyst is the most prevalent type of kidney lesion. Renal cysts are so common that they are seen in around 40% of individuals who undergo imaging. Cystic renal disease can be unilateral, bilateral, or focal. Renal cysts can develop as a consequence of a congenital illness or as a result of an acquired condition. The most prevalent is the acquired form. Renal cysts can be benign or cancerous.

Congenital renal cyst nomenclature has evolved over time, with the current categorization known as the Potter classification. Type I is infantile polycystic kidney disease, type II is multicystic dysplastic kidney disease, type III is adult polycystic kidney disease, and type IV is obstructive renal dysplasia, according to the Potter classifications. Autosomal recessive polycystic kidney disease is another name for infantile polycystic kidney disease (ARPKD). ARPKD has no gender preference, having a ratio of 1:1.

Depending on the severity of the ailment, the diagnosis ranges from neonate through childhood. Multicystic dysplastic kidney disease is a kidney disease that develops in utero and is not inherited. It is usually unilateral, with a larger prevalence on the left side. The diagnosis is frequently made when the baby is still in the womb or very early in life. Autosomal dominant polycystic kidney disease is another name for adult polycystic kidney disease.

A patient with ADPKD has normal kidney appearance at birth and begins to develop numerous cysts bilaterally in their 20s to 30s. It is the most frequent genetic cause of end-stage renal failure, requiring dialysis in more than half of patients by the age of 60. Obstructive cystic renal dysplasia is caused by a developmental blockage that leads in dispersed cysts throughout the damaged kidney.



The prevalence of acquired kidney cysts rises with age. The most prevalent cystic renal lesions are simple renal cysts. They are expected to affect up to 5% of the general population. This incidence rises to more than 25% among persons over the age of 50. Renal cysts can account for up to 65-70 percent of renal masses in the elderly population.

In a 2000-patient retrospective magnetic resonance imaging research, men were shown to have a greater incidence of renal cysts than women. They also found a greater frequency among patients with hypertension and a history of smoking. 



A mutation in the PKHD1 gene on chromosome 6 causes autosomal recessive kidney disease, which results in cyst development in the collecting ducts. Idiopathic multicystic dysplastic kidney disease is the most frequent kind. A mutation in the PKD1 gene on chromosome 16 or the PKD2 gene on chromosome 4 causes autosomal dominant kidney disease.

Obstructive cystic renal dysplasia is caused by a ureter, bladder, or urethra blockage. Idiopathic renal cysts are the most prevalent kind. Renal cysts can arise in an infectious context, as a result of multisystem disorders such Von-Hippel-Lindau and tuberous sclerosis, or as a result of end-stage renal disease.



Multicystic dysplastic kidney disease is characterized by nonfunctioning renal tissue that grows into cysts in the afflicted region. It can eventually result in renal agenesis on the afflicted side. Obstructive cystic renal dysplasia is caused by a blockage of the ureter, bladder, or urethra, which raises pressure in the kidney and causes cysts. 



Kidney Cyst Symptoms

The appearance of a patient with cystic kidney disease differs depending on the underlying cause of the disease. Physical examination is typically only relevant in cases of hereditary renal illness, which manifests as a palpable mass in a newborn or toddler. ADPKD patients frequently appear with flank discomfort, renal failure, hypertension, or palpable masses.

Cystic kidney disease is rarely big enough to be felt on physical examination. Renal cysts are frequently discovered by chance during an ultrasound or cross-sectional imaging for various reasons. A comprehensive family history is essential for understanding potential hereditary variables in a patient with renal cysts.



Kidney Cyst Diagnosis

Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) scans can be used to identify renal cysts (MRI). In most cases, ultrasonography in utero is used to diagnose infantile polycystic kidney disease. Because of the fetus's weak renal function, the mother frequently presents with oligohydramnios. An ultrasound is conducted shortly after delivery, which reveals enlarged kidneys with multiple tiny renal cysts bilaterally.

MRI can be used to further assess the kidneys, which often exhibit a diffuse rise in T2 signal. Multicystic dysplastic kidney disease is often diagnosed in utero rather than in newborns, and it manifests as many noncommunicating renal cysts. Ultrasound or computed tomography (CT) scans are frequently used to diagnose adult polycystic kidney disease.

The presence of more than two cysts per side by the age of 30 aids in diagnosing. Obstructive cystic renal dysplasia is identified in pregnancy when the diseased kidney has a normal to small size and many dispersed cysts.

The ultrasound assessment of a kidney cyst can be divided into two categories: simple and difficult. A simple renal cyst is an anechoic lesion with well-marginated margins and potential posterior acoustic enhancement. A few septations may be present in a minimally complicated cyst. A complicated cyst will have thick septations or walls, as well as hypoechoic or evidence of interior material.

Acquired single or multifocal renal cysts are classified using the Bosniak classification on a contrast-enhanced CT and can be adjusted for MRI use. 

  • A Bosniak I lesion is a round simple cyst with imperceptible walls. There is no need for further testing, and the risk of malignancy is less than 1%.
  • With a few thin septations less than 1 mm in diameter, thin calcification, or a high attenuated lesion less than 3 cm in diameter without enhancement, a Bosniak II lesion has low complexity. Bosniak II lesions do not require follow-up and have a less than 1% probability of cancer.
  • A Bosniak IIF lesion has a low level of complexity, an increased number of thin septations, and possibly "perceived" enhancement with no genuine measured enhancement or a high attenuated lesion bigger than 3 cm. These lesions necessitate further evaluation with CT or ultrasonography. There is no precise interval timeframe provided, however most literature state that it should be done 6 months following diagnosis and then every year for the next 5 years if there is no progression. A Bosniak IIF lesion has a 5% probability of becoming cancerous. 
  • A Bosniak III lesion seems indeterminate, with thick septations and maybe nodularity or detectable wall enhancement more than ten Hounsfield units. The preferred therapy is a biopsy and partial nephrectomy rather than ablation. A Bosniak III lesion has a 55% probability of being cancerous.
  • A Bosniak IV lesion is defined as a solid mass that has cystic versus necrotic components. These are described as certainly cancerous. The preferred therapy is nephrectomy, either partial or complete. The Bosniak IV lesion has a one hundred percent likelihood of being cancerous.

A simple cyst on MRI will demonstrate a low T1 signal, high T2 signal, with no evidence of enhancement post-contrast.


CT scan 

CT scans of the kidneys might reveal cysts and malignancies. A CT scan creates pictures of your urinary system by using x-rays and computer technologies. Although a CT scan without contrast medium is the most typical technique to observe your urinary system, a health care practitioner may administer a contrast medium injection to you. A contrast medium is a dye or other material that helps imaging tests view things within your body more clearly. You'll recline on a table that slides into a tunnel-shaped equipment that captures x-rays for a CT scan.



Kidney Cyst Management

Simple kidney cysts that cause symptoms or obstruct the normal passage of blood or urine through the kidney may require treatment with sclerotherapy, in which the cyst is pierced with a long needle guided by ultrasonography. To harden the cyst, it is drained and filled with an alcohol-containing solution. Sclerotherapies are commonly performed as an outpatient procedure using a local anesthetic. You will not need to stay in a hospital overnight if you get this surgery.

If the cyst is large enough, a procedure called as a laparoscopy may be required. These procedures are carried out with the use of a laparoscope, which is a tube with a tiny, lit video camera at one end. This surgery is carried out by a surgeon and necessitates general anesthesia. The cyst is drained and either removed or burnt during this operation to prevent it from returning. You may need to stay in the hospital for one or two days if you get this surgery.

Treatment for infantile polycystic kidney disease is primarily supportive, including dialysis and transplant, although patients have a poor prognosis overall. The controversial therapy for multicystic dysplastic kidney disease is nephrectomy of the afflicted side.

If a nephrectomy is not performed, a follow-up examination is advised due to the minimal chance of malignant change. As long as the contralateral kidney functions normally, the patients will have a normal life expectancy. Adult polycystic kidney disease is the most common genetic cause of end-stage kidney disease, necessitating dialysis and transplantation in the great majority of patients by middle life to the early 60s. The blockage is removed to treat obstructive cystic renal dysplasia.

Lesions identified as Bosniak I and II do not require additional assessment. A Bosniak IIF suggests a follow-up ultrasound or CT scan. A Bosniak III suggests surgical surgery, which includes a biopsy and partial nephrectomy or ablation. A Bosniak IV advises nephrectomy, either partial or complete.

If you are above the age of 50, there is a strong possibility you have kidney cysts and are unaware of it. You could not know it because you don't have any symptoms. Furthermore, the majority of kidney cysts do not cause any complications. Consult your doctor if you have any symptoms (back or stomach discomfort, blood in your urine, etc.). He or she can counsel you on a course of therapy or methods to alleviate your problems.


How do health care professionals treat the complications of simple kidney cysts?

Simple kidney cysts that do not cause symptoms are typically not treated by medical specialists. However, you may be required to have regular ultrasounds to monitor any changes or concerns with your minor kidney cysts.

Simple kidney cysts that cause symptoms such as discomfort or that restrict the passage of blood or urine will be treated by medical specialists. According to some research, draining or eliminating the cysts may assist with high blood pressure caused by simple kidney cysts. Researchers are unsure how or why this operates.



Sclerotherapy is a procedure used to drain cysts. A health care practitioner inserts a long needle through your skin and into the cyst using ultrasonography as a guide. The cyst is drained and an alcohol solution is injected by the doctor. The treatment hardens the interior of the cyst, making it less likely to fill up with fluid again. This operation is normally done in an outpatient setting under local anaesthetic.



If the cyst is big, laparoscopic surgery may be required. The cyst is drained and then the cyst's exterior tissue is removed or burned away by the surgeon. You may require general anesthesia at a hospital for this surgery. You might need to stay in the hospital for a day or two.


Differential Diagnosis

If the patient has a symptomatic renal cyst, such as stomach discomfort or urine blockage, the differential is extensive. Because the kidneys are bilateral structures, practically every organ might be involved in the discomfort induced by a renal cyst. It is important to note, however, that most renal cysts are asymptomatic and are discovered by chance. A symptomatic cyst's differential diagnosis includes, but is not limited to:

  • Kidney stones
  • Pyelonephritis
  • Adrenal neoplasm
  • Renal neoplasm
  • Splenic infarction
  • Hernia
  • Trauma
  • Gallbladder disease



The prognosis of renal cysts varies greatly depending on their genesis. Simple Bosniak type I cysts have a less than 1% incidence of malignancy, but Bosniak type IV cysts have a higher likelihood of malignancy and a poorer prognosis. In recessive (pediatric) polycystic kidney disease, roughly 30% of patients do not survive their first week of birth, and those who do survive will require lifelong dialysis or a kidney transplant, as well as frequently having cystic liver disease.

The development of dominant (adult) polycystic kidney disease varies, but if it advances to end-stage renal disease, the patient will need dialysis or a kidney transplant.



As previously said, the prognosis of renal cysts and the difficulties that might emerge as a result of cysts, as well as their treatment, vary greatly depending on the etiology of the cyst. Bosniak type I cysts may be safely examined and so offer no danger of complication, however Bosniak type IV cysts may necessitate extensive surgery, which has a high risk of consequences such as injury to nearby tissues such as the liver, spleen, or stomach.

Those with recessive (pediatric) polycystic kidney disease who survive their first few weeks of birth, as well as patients with dominant (adult) polycystic kidney disease who proceed to end-stage renal disease, will require lifetime dialysis or kidney transplant. Infections or damage to vascular structures might make dialysis more difficult.

Patients who undergo transplants are at a higher risk of infection due to immunosuppression as well as the complication profile that comes with the significant surgery involved in a transplant operation.


Clinical Trials for Simple Kidney Cysts

Clinical trials are a component of clinical research and are important to all medical achievements. Clinical trials investigate novel approaches to illness prevention, detection, and treatment. Clinical trials are also used by researchers to investigate other elements of treatment, such as increasing the quality of life for persons with chronic diseases.



The most common kidney lesion is a renal cyst. Renal cysts are so common that they are seen in around 40% of individuals who undergo imaging. Cystic renal disease can be unilateral, bilateral, or focal. Renal cysts can develop as a consequence of a congenital illness or as a result of an acquired condition. The most prevalent is the acquired form. Renal cysts can be benign or cancerous.

While there is no method to prevent renal cysts from forming, it is critical to educate patients who acquire or inherit them on the nature of their cysts. Patients who have unintentionally discovered Bosniak type I or II cysts should be informed that there is a low risk of cancer and that no planned follow-up is necessary. Patients with Bosniak type IIF cysts should be counseled on the need of attending follow-up appointments to ensure the cyst does not develop.

Patients with Bosniak type II or IV cysts should be educated about their cancer risk, and a long-term care plan should be devised for both cyst excision and postoperative treatment. Patients with recessive (pediatric) polycystic kidney disease should be educated about their child's lifelong need for dialysis, as well as the prospect of a kidney donation in the future.

Patients with dominant (adult) polycystic kidney disease who proceed to end-stage renal disease should also be informed about dialysis and the prospect of a future kidney donation.