Evaluation of Renal Masses

Initial Imaging Evaluation

The American College of Radiology recommends obtaining high-quality multiphase cross-sectional abdominal imaging (CT or MRI with IV contrast) to characterize the mass, followed by comprehensive metabolic panel, complete blood count, urinalysis, and chest imaging to evaluate for metastases 1
Dedicated renal protocol CT or MRI with assessment of tumor complexity, degree of contrast enhancement, and presence or absence of fat is mandatory to optimally characterize and clinically stage any solid or complex cystic renal mass 1
Unenhanced phase is necessary to measure baseline attenuation and identify calcifications, while arterial and nephrographic phases are required to assess enhancement patterns 2

Homogeneous masses <20 HU or >70 HU on unenhanced CT are benign and require no further workup, according to the Journal of the American College of Radiology 2
Masses 20-70 HU on unenhanced CT are indeterminate and require multiphase evaluation 2
Homogeneous masses 10-20 HU on portal venous phase contrast CT are benign cysts 2
Recent evidence suggests masses 21-30 HU on portal venous phase may also be benign cysts and do not require further evaluation 2

The American Urological Association recommends obtaining comprehensive metabolic panel, complete blood count, urinalysis, lactate dehydrogenase, C-reactive protein, corrected serum calcium, alkaline phosphatase, and liver function tests in all patients with suspected renal malignancy 1, 3, 4
Classify chronic kidney disease stage based on eGFR and degree of proteinuria using KDIGO guidelines, as this directly impacts treatment options 1

Chest imaging is mandatory as the lungs are the most common site of metastasis for renal cell carcinoma, according to the American College of Radiology 1, 3
Do not routinely obtain bone scan, brain imaging, or PET scan, unless specific symptoms or findings suggest their necessity 4, 5

Consider renal mass biopsy in specific scenarios, including before ablative therapies, in patients with metastatic disease, when risk/benefit analysis for treatment is equivocal, and for masses that remain indeterminate after optimal cross-sectional imaging 3, 5
Renal mass biopsy provides histopathological confirmation with high sensitivity and specificity, according to the American Urological Association 3

Genetic counseling should be offered to patients ≤46 years of age, those with multifocal or bilateral renal masses, and those with personal or family history suggesting familial renal neoplastic syndrome (von Hippel-Lindau, hereditary leiomyomatosis, etc.) 3, 4, 5
Approximately 6-9% of renal cancers have germline mutations in cancer predisposition genes, according to the American College of Medical Genetics 3

A urologist should lead the counseling process and discuss all management options, including partial nephrectomy, radical nephrectomy, thermal ablation, and active surveillance, according to the American Urological Association 1
Key counseling points include current perspectives on tumor biology, natural history based on size and imaging characteristics, oncologic risks versus treatment-related morbidity, impact on renal function, and patient's overall health status, comorbidities, and life expectancy 1, 3, 4

Suboptimal imaging technique is a frequent cause of diagnostic errors—ensure dedicated multiphase renal protocol is used rather than single-phase imaging 6
Do not assume all enhancing masses are malignant—approximately 20% of surgically resected small renal masses are benign, according to the American College of Radiology 6
Avoid radical nephrectomy as first-line treatment for clinical T1a lesions; partial nephrectomy is preferred to preserve renal function, according to the American Urological Association 6, 7
Do not delay nephrology referral in patients with CKD, as appropriate management can prevent further deterioration affecting bone health, metabolic health, and cardiovascular risk, according to the National Kidney Foundation 5