What are the implications of a large simple renal cyst (kidney cyst)?

From the Guidelines

A large simple renal cyst is typically benign and requires no specific treatment if it is asymptomatic and meets benign criteria on imaging, such as a Bosniak category I classification 1. These cysts are fluid-filled sacs that develop in the kidneys and are usually discovered incidentally during imaging studies performed for other reasons.

• Key characteristics of a simple cyst include thin walls, no internal echoes or septations, no calcifications, and no solid components on ultrasound or CT scan.
• The Bosniak classification system, updated in 2019, is used to categorize renal cystic masses and predict the risk of malignancy, with Bosniak I cysts having a 0% risk of malignancy 1.
• If the cyst is causing symptoms such as pain, infection, or obstruction of urinary flow, treatment options include percutaneous aspiration with or without sclerotherapy, or surgical removal (laparoscopic or open unroofing/decortication) in severe cases.
• Follow-up imaging is recommended for large cysts (>3 cm) at 6-12 month intervals initially to ensure stability, as most simple kidney cysts remain benign and do not progress to kidney cancer 1.
• It is essential to note that complex cysts with concerning features, such as Bosniak III or IV cysts, require more aggressive evaluation and management due to their higher risk of malignancy, with approximately 50% and 100% of surgically treated cases being malignant, respectively 1.

From the Research

Implications of a Large Simple Renal Cyst

• A large simple renal cyst can cause symptoms such as back pain and abdominal fullness, as reported in a case study 2.
• Simple renal cysts are common in adults, but most of them are asymptomatic 2, 3, 4.
• However, large symptomatic simple renal cysts can cause complications such as hemorrhage, infection, hydronephrosis, and hypertension 3, 5, 4.
• The management of simple cysts is entirely for its symptoms or complications, and percutaneous aspiration alone or with sclerotherapy is often the first-line treatment 3.
• Surgical decortication, including laparoscopic surgery, is generally reserved for recurrent or very large symptomatic cysts 3, 6.
• Laparoscopic renal cyst decortication has become the standard of care for management of large symptomatic simple renal cysts, and it can be performed in an ambulatory setting 6.
• The procedure is minimally invasive and safe, with high satisfaction rates and minimal morbidity 2, 3, 6.

Treatment Options

• Percutaneous aspiration alone or with sclerotherapy is often the first-line treatment for simple renal cysts 3, 5.
• Laparoscopic surgery, including retroperitoneal approach, is highly efficacious and is associated with high satisfaction rates with minimal morbidity 3, 6.
• Surgical decortication can be performed using conventional monopolar devices or sealing devices, and it is an effective and safe treatment option for symptomatic simple renal cysts 2, 3.
• Robot-assisted surgical management can be used for complex cysts, but it has added cost and no outstanding benefits 3.

Complications and Associations

• Large simple renal cysts can cause complications such as hemorrhage, infection, hydronephrosis, and hypertension 3, 5, 4.
• There is a possible association between renal cysts and arterial hypertension, and renal cysts may produce segmental renal ischemia and activate the renin angiotensin system 4.
• Percutaneous cyst aspiration or surgical cyst removal could cause a fall in blood pressure 4.