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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 62-year-old man comes to the clinic to review imaging results. He originally presented to an urgent care center two days ago with left-sided flank pain, and an unenhanced computed tomography (CT) scan of the abdomen and pelvis was performed to evaluate for suspected nephrolithiasis. The scan revealed a 4-mm non-obstructing stone in the left kidney, but it also incidentally demonstrated a 4.5-cm, solid, heterogeneous mass in the upper pole of the right kidney. The patient has a 30-pack-year smoking history but denies gross hematuria, fever, bone pain, or unintentional weight loss. Vital signs are temperature 37.0 C (98.6 F), blood pressure 138/86 mm Hg, heart rate 78/min, and respiratory rate 14/min. Physical examination reveals a soft, non-tender abdomen with no palpable masses. Which of the following represent the most appropriate concurrent next steps in this patient's diagnostic workup? (Select all that apply)

  1. Contrast-enhanced computed tomography of the abdomen and pelvisAnswer
  2. Chest radiographAnswer
  3. Comprehensive metabolic panelAnswer
  4. D
    Percutaneous core needle biopsy of the right renal mass
  5. E
    Whole-body positron emission tomography (PET) scan

Answer

The most appropriate initial concurrent diagnostic steps for evaluating an incidental solid renal mass include contrast-enhanced cross-sectional abdominal and pelvic imaging, a baseline chest radiograph, and a comprehensive metabolic panel.
For a newly discovered solid renal mass suspicious for renal cell carcinoma (RCC), the initial diagnostic sequence involves characterizing the primary tumor, establishing baseline physiologic parameters, and ruling out common sites of metastasis. Contrast-enhanced computed tomography (or MRI) of the abdomen and pelvis is essential to determine if the mass enhances (the hallmark of RCC), assess for regional lymph node involvement, and evaluate the renal vein and inferior vena cava for tumor thrombus extension. A chest radiograph is indicated as the initial screening test for pulmonary metastases, which are the most common site of distant RCC spread (though a chest CT is also acceptable and often obtained). A comprehensive metabolic panel is necessary to evaluate baseline renal function prior to the administration of intravenous contrast media, and to assess for paraneoplastic hypercalcemia or elevated liver enzymes, which could suggest liver metastases or Stauffer syndrome.

Step-by-Step Solution

1
Identify the primary clinical problem from the vignette.
The patient has an incidental 4.5-cm, solid, heterogeneous mass in the right kidney, which is highly suspicious for renal cell carcinoma (RCC).
Recognizing the high probability of malignancy dictates the subsequent diagnostic pathway, which focuses on characterization and staging.
2
Determine the necessary anatomic and staging imaging required.
Contrast-enhanced CT (or MRI) of the abdomen and pelvis is needed to confirm the diagnosis (via mass enhancement) and check for local invasion. A chest radiograph is needed to screen for pulmonary metastases.
Unenhanced CT cannot reliably distinguish between a benign cyst, a hemorrhagic cyst, and a solid tumor. The lungs are the most common site of RCC metastasis.
3
Identify necessary baseline laboratory studies.
A comprehensive metabolic panel (CMP) should be ordered.
A CMP assesses baseline creatinine before intravenous contrast administration, checks calcium levels for paraneoplastic hypercalcemia, and evaluates liver enzymes for metastases or Stauffer syndrome (non-metastatic hepatic dysfunction).

Key Concept

Initial diagnostic staging and test sequencing for a newly discovered solid renal mass.
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Topics

Diagnostic Workup and Test Sequencing

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