What are the next steps after a PET scan showing a right upper lobe and hilar mass with local nodal metastases and moderate left hydronephrosis concerning for UPJ obstruction?

Management of PET Scan Findings: Right Upper Lobe Mass with Nodal Metastases and Left Hydronephrosis

The next step after this PET scan should be a tissue biopsy of the right upper lobe mass via CT-guided percutaneous needle biopsy to confirm malignancy and determine histological subtype. 1

Lung Mass Management

Tissue Diagnosis

• A pretreatment pathological diagnosis is strongly recommended before any curative treatment for the lung mass 1
• CT-guided percutaneous lung biopsy is rated as "usually appropriate" (rating 8/9) for patients with suspected lung cancer and risk factors 1
• Endoscopic techniques may be considered if the mass is centrally located, but the description suggests a peripheral upper lobe mass which is more amenable to percutaneous approach

Rationale for Percutaneous Approach

• The PET scan already shows local nodal metastases, suggesting at least stage II-III disease
• Percutaneous biopsy provides:
  • Definitive tissue diagnosis
  • Histological subtype determination (critical for treatment planning)
  • Potential for molecular testing if non-small cell lung cancer is found
  • Avoidance of more invasive surgical procedures 1

Mediastinal Staging

• After tissue diagnosis, invasive mediastinal staging will be required to confirm the nodal involvement seen on PET
• For patients with abnormal mediastinal lymph nodes on PET, endosonography (EBUS/EUS) is recommended over surgical staging 1
• If EBUS/EUS is negative in the setting of high clinical suspicion, mediastinoscopy is indicated 1

Management of Left Hydronephrosis

Concurrent Urological Evaluation

• The moderate left hydronephrosis with normal ureter requires urological consultation
• Given the concern for UPJ obstruction, a functional study should be performed:
  • Diuretic renal scan to assess the degree of obstruction and renal function 2
  • This can be scheduled concurrently with the lung mass workup

Potential Causes to Consider

• While primary UPJ obstruction is possible, in the context of malignancy, consider:
  • Metastatic involvement of the retroperitoneum
  • Extrinsic compression from lymphadenopathy
  • Direct tumor extension if the primary is near the kidney

Comprehensive Approach

1. First priority: CT-guided percutaneous biopsy of the lung mass
2. Second priority: Urological consultation with diuretic renal scan for hydronephrosis
3. Third priority: Based on lung biopsy results:
   • If malignant: Complete staging workup including brain MRI 1
   • Invasive mediastinal staging via EBUS/EUS 1
   • Multidisciplinary tumor board discussion for treatment planning

Common Pitfalls to Avoid

• Delaying tissue diagnosis while pursuing additional imaging
• Assuming the hydronephrosis is unrelated to the lung mass without proper evaluation
• Proceeding directly to surgery without adequate mediastinal staging
• Neglecting brain MRI in the complete staging workup for lung cancer with nodal involvement

The presence of both a lung mass with nodal involvement and hydronephrosis requires a coordinated approach between thoracic oncology and urology to ensure comprehensive management of both conditions.