What is the appropriate management for a patient with a 9mm nonobstructing calculus in the lower pole of the right kidney and a 1.5cm echogenic lesion in the right mid kidney, suggestive of an angiomyolipoma (AML), and a borderline enlarged spleen?

Management of Incidental Renal Findings

Immediate Next Step: Obtain CT Abdomen with and without Contrast

You should proceed with CT abdomen with and without IV contrast to definitively characterize the 1.5cm echogenic renal lesion, as ultrasound alone cannot reliably distinguish between benign angiomyolipoma and renal cell carcinoma. 1

The CT will determine if macroscopic fat is present (confirming classic angiomyolipoma) or if the lesion is fat-poor, which would require further evaluation. 1

Management Algorithm for the 1.5cm Renal Lesion

If CT Confirms Classic Angiomyolipoma (Fat-Containing):

• Lesions <4cm without aneurysms ≥5mm can be managed with active surveillance 2
• Schedule follow-up imaging at 1-3 year intervals using the same imaging modality (CT or MRI) to assess for growth 1
• The risk of spontaneous hemorrhage is approximately 5% and increases with lesion size >4cm or presence of aneurysms ≥5mm 1, 2
• No immediate intervention is needed for a 1.5cm lesion unless symptomatic 3, 2

If CT Shows Fat-Poor or Indeterminate Lesion:

• Consider renal mass biopsy, as imaging features suggestive of fat-poor AML warrant tissue diagnosis to exclude renal cell carcinoma 1
• Biopsy is particularly important because benign tumors (including fat-poor AML and oncocytoma) comprise up to 25% of small renal masses but cannot be reliably distinguished from RCC on imaging alone 1
• The diagnostic yield of biopsy for lesions <4cm is approximately 80%, with complication rates <1% 1
• If biopsy is nondiagnostic, this cannot be considered evidence of benignity and repeat biopsy or surgical excision should be considered 1

If Biopsy Confirms Renal Cell Carcinoma:

• Partial nephrectomy is the standard treatment for small renal masses ≤4cm that are amenable to nephron-sparing surgery 1
• Refer to urology/urologic oncology for surgical evaluation 1
• Active surveillance is an alternative only if the patient has significant comorbidities and limited life expectancy (<5 years) 1

Management of the 9mm Nonobstructing Lower Pole Calculus

Current Management:

• Active surveillance is appropriate for asymptomatic, nonobstructing lower pole stones up to 15mm 4
• Schedule follow-up imaging to monitor for stone growth, as growth on serial imaging is an indication for intervention 5
• Lower pole stones are less likely to pass spontaneously (only 2.9% passage rate) compared to upper/mid pole stones (14.5%) 6
• Approximately 24-28% of asymptomatic lower pole stones will become symptomatic over 3+ years of follow-up 6

Indications for Intervention:

Proceed to surgical treatment if any of the following develop: 5, 4

• Intractable pain despite medical management
• Progressive hydronephrosis or declining renal function
• Urinary tract infection with obstruction
• Stone growth on follow-up imaging
• Patient develops symptoms

Treatment Options if Intervention Becomes Necessary:

• For symptomatic lower pole stones ≤10mm: Either shock wave lithotripsy (SWL) or flexible ureteroscopy (fURS) are first-line options 4
• fURS provides higher stone-free rates (81-90%) compared to SWL (58-72%), but SWL offers better quality of life outcomes 4
• Do NOT offer SWL as first-line therapy if the stone grows >10mm, as success rates drop dramatically 5, 4
• For stones 10-20mm, ureteroscopy or percutaneous nephrolithotomy (PCNL) are recommended 4

Management of Borderline Enlarged Spleen

• The spleen finding is likely incidental and unrelated to the renal pathology
• If no other clinical signs of liver disease, portal hypertension, hematologic disorder, or infection are present, no immediate workup is needed
• Consider basic laboratory evaluation: complete blood count, liver function tests, and peripheral smear if any cytopenias are present
• Refer to hematology only if laboratory abnormalities suggest underlying hematologic disorder

Referral Recommendations

Immediate Referrals Needed:

1. Radiology: Schedule CT abdomen with and without contrast urgently (within 2-4 weeks) 1

Subsequent Referrals Based on CT Results:

1. Interventional Radiology or Urology: For renal mass biopsy if lesion is fat-poor or indeterminate 1

2. Urology/Urologic Oncology: If biopsy confirms RCC or if imaging characteristics are highly suspicious for malignancy 1

3. Nephrology: Consider referral if chronic kidney disease develops (eGFR <45 mL/min/1.73m²) or if progressive CKD occurs after any intervention 1

Critical Pitfalls to Avoid

• Do not assume the echogenic lesion is benign without CT confirmation of macroscopic fat, as up to 8% of RCCs are hyperechoic on ultrasound 1
• Do not delay CT imaging beyond 4-6 weeks, as this could allow progression of undiagnosed malignancy 5
• Do not intervene on the kidney stone unless it becomes symptomatic, grows, or causes obstruction/infection 5, 4, 6
• Do not use different imaging modalities for serial follow-up, as this makes accurate size comparison impossible 1
• Do not assume a nondiagnostic biopsy means the lesion is benign—this requires repeat biopsy or surgical excision 1