What is the approach to managing renal masses?

Approach to Renal Masses

For any newly detected renal mass, obtain high-quality multiphase cross-sectional imaging (CT or MRI with and without contrast) to characterize enhancement patterns, assess complexity, detect fat content, and clinically stage the lesion. 1

Initial Diagnostic Evaluation

Imaging Requirements

• Multiphase contrast-enhanced CT or MRI is mandatory to assess tumor complexity, degree of enhancement, presence/absence of fat, and anatomic relationships 1
• Characterization must include evaluation for locally invasive features, venous involvement, and contralateral kidney status 1, 2
• For suspected malignancy, obtain chest imaging to evaluate for thoracic metastases 1

Laboratory Assessment

• Obtain comprehensive metabolic panel (including calculated GFR), complete blood count, and urinalysis 1
• Assign CKD stage based on GFR and degree of proteinuria for all patients with solid or Bosniak 3/4 complex cystic masses 1
• Evaluate for proteinuria, hematuria, hypercalcemia, hepatic dysfunction, and blood count abnormalities 1

Role of Renal Mass Biopsy

Perform renal mass biopsy in three specific scenarios: 1, 3

1. Prior to all thermal ablation procedures (mandatory) 1
2. When clinical/radiographic findings suggest lymphoma, abscess, or metastasis 1
3. For indeterminate masses where histological diagnosis would alter management, particularly when imaging features are non-diagnostic 3

• Biopsy is safe with major complications occurring in <1% of cases 3
• The American College of Radiology endorses biopsy for diagnostic purposes to guide treatment decisions and minimize unnecessary kidney function loss 3

Management Strategy by Clinical Stage

cT1a Renal Masses (≤4 cm)

Prioritize partial nephrectomy as first-line intervention when treatment is indicated 1

Treatment Options:

• Partial nephrectomy (PN): Standard of care; both open and laparoscopic approaches acceptable based on tumor location and surgeon expertise 1
• Thermal ablation (TA): Consider as alternate approach for masses <3 cm, preferably via percutaneous route 1
  • Both radiofrequency ablation and cryoablation are acceptable 1
  • Requires pre-procedure biopsy 1
  • Higher likelihood of tumor persistence/recurrence compared to PN 1
• Active surveillance: Consider for solid masses <2 cm or predominantly cystic Bosniak 3-4 lesions, particularly in patients with competing mortality risks 1

Special Considerations for cT1a:

• Approximately 20% of enhancing cT1 masses are benign 1
• Only 20-25% of RCC in this size range demonstrate aggressive variants 1
• Counsel patients about the low oncologic risk of many small renal masses 1

cT1b Renal Masses (>4-7 cm)

Partial nephrectomy remains the priority nephron-sparing approach 1

• PN should be strongly considered even for larger cT1b tumors when technically feasible 1
• Radical nephrectomy is acceptable if PN is not technically feasible as determined by the urologic surgeon 1

Locally Advanced Disease (cT3a and Beyond)

Open radical nephrectomy with regional lymph node dissection is the standard approach for cT3a disease with nodal involvement 2

• Laparoscopic approaches may be considered in highly selected cases with adequate surgical expertise 2
• Perform regional lymph node dissection for clinical N1 status for both staging and potential therapeutic benefit 2
• Avoid systematic adrenalectomy unless imaging demonstrates direct adrenal involvement 2

Imperative Indications for Nephron-Sparing Surgery

Prioritize nephron-sparing approaches (PN or TA) in the following scenarios: 1

• Anatomic or functionally solitary kidney 1
• Bilateral renal tumors 1
• Known familial RCC syndromes 1
• Pre-existing CKD (GFR <60) 1
• Confirmed proteinuria 1
• Young patients 1
• Multifocal masses 1
• Comorbidities likely to impact future renal function (diabetes, hypertension) 1

Renal Function Considerations

Nephrology Referral Criteria

Refer to nephrology when: 1

• GFR <45 mL/min/1.73m² 1
• Confirmed proteinuria present 1
• Diabetics with pre-existing CKD 1
• Expected post-intervention GFR <30 mL/min/1.73m² 1, 2

Functional Outcomes

• Radical nephrectomy increases risk of CKD, which correlates with increased cardiovascular morbidity and mortality 1
• Management should focus on optimizing renal function, not merely avoiding dialysis 1
• For PN in solitary kidneys, dialysis-free survival is 97% at 5 years 4

Genetic Counseling

Recommend genetic counseling for: 1

• All patients ≤46 years of age 1
• Patients with multifocal or bilateral renal masses 1
• Personal or family history suggesting familial renal neoplastic syndrome 1

Counseling Framework

A urologist should lead the counseling process with multidisciplinary team involvement when necessary 1

Essential Counseling Elements:

• Current perspectives on tumor biology and patient-specific oncologic risk assessment 1
• Most common and serious urologic/non-urologic morbidities of each treatment pathway 1
• Importance of patient age, comorbidities/frailty, and life expectancy 1
• Renal functional recovery considerations, including CKD progression risk, potential dialysis need, and long-term survival 1
• Natural history of clinical stage 1 renal masses and relative risks of benign versus malignant pathology 1

Special Populations

Renal Mass in Solitary Kidney

• PN is feasible and successful in 82% of cases 4
• Selective use of tyrosine kinase inhibitors (TKIs) can facilitate PN by reducing tumor volume (median 57% decrease) in patients with clear-cell RCC and high RENAL scores (≥10) 4
• RN is occasionally required (4-5% of cases) due to severe pre-existing CKD or overriding oncologic concerns 4
• Five-year recurrence-free survival: PN 83%, cryoablation 80%, RN 72% 4

Bilateral Angiomyolipomas

• Active surveillance with imaging every 1-3 years is the initial approach for lesions <4 cm 5
• Intervention reserved for lesions >4 cm, substantial bleeding risk factors (intralesional aneurysms ≥5 mm, growth >5 mm/year), or symptomatic presentations 5
• mTORC1 inhibitors (everolimus or sirolimus) are first-line treatment when intervention required 5

Critical Pitfalls to Avoid

• Do not perform radical nephrectomy reflexively for cT1a masses; PN is greatly underutilized and often feasible even for central/hilar tumors with adequate expertise 1
• Do not skip renal mass biopsy before thermal ablation—it is mandatory 1
• Do not ignore renal functional assessment—CKD staging must be performed for all patients with suspected malignancy 1
• Do not initiate treatment without high-quality cross-sectional imaging—inadequate imaging leads to suboptimal management decisions 1, 6
• Do not perform systematic adrenalectomy unless direct adrenal involvement is demonstrated 2