What is the recommended management and treatment approach for a patient with renal cysts, considering their size, growth, and potential symptoms, as well as their medical history of kidney disease, hypertension, or other renal issues?

Management of Renal Cysts

Distinguish Between Simple Renal Cysts and Autosomal Dominant Polycystic Kidney Disease (ADPKD)

The management approach fundamentally differs based on whether you are dealing with simple renal cysts versus ADPKD—simple cysts in asymptomatic patients require no treatment or follow-up, while ADPKD demands systematic monitoring and intervention for hypertension and proteinuria. 1

Simple Renal Cysts

For asymptomatic simple renal cysts, no treatment or follow-up is necessary. 1

• Ultrasonography is the first-line imaging modality to characterize cysts and rule out complications like stones or urinary tract obstruction. 2
• Simple cysts are extremely common, found in nearly one-third of patients over 50 years old. 3
• If the cyst shape is slightly irregular, mandatory follow-up is required to exclude malignant progression. 1

When Simple Cysts Require Intervention

Symptomatic cysts require radiological intervention with sclerosant injection, not simple aspiration alone. 1

• Simple fluid aspiration is ineffective and leads to cyst recurrence. 1
• Ethanol in high concentrations with multiple injections is the most commonly used sclerosant, achieving high rates of cyst disappearance and long-lasting volume reduction. 1
• Large cysts (particularly >1 cm diameter) associated with hypertension may warrant intervention, especially when bilateral, multiple (≥2 cysts), or causing local tissue compression that activates the renin-angiotensin system. 3, 4
• Percutaneous needle aspiration with renal venous renin determination can help establish causality between large cysts and hypertension. 3

Autosomal Dominant Polycystic Kidney Disease (ADPKD)

Diagnostic Approach

Ultrasonography is the preferred diagnostic and monitoring tool for ADPKD in children and adults. 5, 2

• In children under 15 years with positive family history, detection of one or more kidney cysts on ultrasound is highly suggestive of ADPKD. 5, 2
• A normal ultrasound in an at-risk child does not exclude ADPKD, and rescreening intervals should not be shorter than 3 years. 5
• Multiple cysts with negative family history require clinical work-up for other cystic kidney diseases. 5
• MRI is more sensitive than ultrasonography for cyst detection but requires sedation in young children and is not the first-line diagnostic method. 5

Core Clinical Monitoring

Regular blood pressure monitoring is the most essential clinical intervention, as hypertension affects 6-22% of children with ADPKD and correlates with kidney volume and disease progression. 5, 2, 6

• Proteinuria monitoring with laboratory-measured albumin-to-creatinine ratio (ACR) is standard care, as proteinuria is one of the most established risk factors for CKD progression regardless of age. 5, 6
• Routine monitoring of cyst growth in asymptomatic patients should not be performed frequently, as ultrasonography findings rarely influence clinical management and impose psychological burden. 5
• eGFR remains nearly always within normal range during childhood ADPKD, making eGFR decline a suitable progression marker only in the small subgroup with very advanced disease. 5, 6

Blood Pressure Management

Use renin-angiotensin system inhibitors (ACE inhibitors or ARBs) as first-line treatment to achieve target blood pressure. 5

• For patients aged 18-49 years with CKD G1-G2 and BP >130/85 mmHg, target home BP of ≤110/75 mmHg if tolerated. 5
• For patients aged ≥50 years and/or with CKD G3-G5, target mean systolic BP <120 mmHg using standardized office measurement. 5
• Avoid any combination of ACE inhibitor, ARB, and direct renin-inhibitor therapy. 5
• Diuretics should be used with caution as they may increase vasopressin levels and have deleterious effects on eGFR compared to ACE inhibitors. 5

Proteinuria Management

In patients with ADPKD who have proteinuria, use ACE inhibitors or ARBs as primary treatment, as reduction of proteinuria is associated with significant improvement in renal survival. 5, 6

• Measure ACR in laboratory rather than dipstick testing for greater sensitivity and specificity. 5
• The prevalence of proteinuria in children with ADPKD is approximately 20%. 5

Lifestyle Interventions

Children with ADPKD should achieve the recommended salt intake for healthy children, which may require dietician assistance. 5, 2

• Higher urinary sodium levels increase the risk of 50% eGFR reduction, ESRD, or death in patients with later-stage ADPKD. 5, 6
• Restricting salt intake lowers blood pressure and proteinuria in adults with ADPKD or CKD. 5

Maintaining normal weight is essential, as obesity independently predicts faster renal function loss in adults with early ADPKD. 5, 2

Avoid dehydration and encourage drinking to satisfy thirst, but high water intake to suppress vasopressin has not been proven beneficial in interventional studies. 5, 2

• Unnecessary protein restriction should be avoided in children to reduce risk of malnutrition. 5

Pain Management

Flank, abdominal, or lumbar pain requires investigation with ultrasonography to identify cyst hemorrhage, infection, stones, or urinary tract obstruction. 5

• Longitudinal eGFR slope can aid in identifying pain caused by cyst enlargement. 5
• Spinal-cord stimulation may provide significant pain relief in specific cases of moderate-to-severe refractory mechanical or visceral pain. 5
• Nephrectomy is reserved for severe intractable pain, typically with advanced kidney disease or after kidney failure, in those who have failed other modalities. 5

Disease-Modifying Therapy

Tolvaptan should be used specifically for patients at risk of rapidly progressive disease, demonstrating a net difference in eGFR decline of 1.3 ml/min per 1.73 m² per year compared to untreated patients. 6

• Approximately 3% of children with ADPKD develop very-early-onset or unusually rapid progressive disease. 6
• Most patients with ADPKD experience slow, gradual progression, with kidney failure typically occurring after the fourth decade of life. 6

Screening for Extrarenal Manifestations

Do not screen for mitral valve prolapse in children without a heart murmur. 2

Do not screen for intracranial aneurysms in children. 2

Do not screen regularly for liver cysts. 2

Monitoring Strategy Based on Kidney Function

For patients with eGFR 45-60 mL/min/1.73 m²: monitor eGFR every 6 months and electrolytes, bicarbonate, hemoglobin, calcium, phosphorus, PTH at least yearly. 7

For patients with eGFR 30-44 mL/min/1.73 m²: monitor eGFR every 3 months and comprehensive metabolic parameters every 3-6 months. 7

Refer to nephrologist for eGFR <30 mL/min/1.73 m², rapidly progressive kidney disease (>30% decline in eGFR within 4 weeks), resistant hypertension, or difficult management issues. 7