A 59-year-old man is evaluated in the emergency department for severe, colicky left flank … — USMLE Step 3

A $59$ -year-old man is evaluated in the emergency department for severe, colicky left flank pain that began $4$ hours ago. He has no significant past medical history. His temperature is $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure is $142/85\text{ mm Hg}$ , and pulse is $88\text{/min}$ . Physical examination demonstrates left costovertebral angle tenderness. Urinalysis reveals $25$ - $30\text{ erythrocytes/hpf}$ . A non-contrast computed tomography (CT) scan of the abdomen and pelvis reveals a $4\text{-mm}$ obstructing calculus in the distal left ureter. Additionally, an incidental $4.5\text{-cm}$ cystic mass is identified in the upper pole of the right kidney. To further characterize this mass, a contrast-enhanced CT protocol is performed. The post-contrast images demonstrate that the right renal cyst contains multiple thick, irregular septations and several distinct soft-tissue mural nodules with measurable enhancement.

Based on the imaging characteristics of the right renal mass, which of the following is the most appropriate next step in management?

A
Reassurance and no further evaluation
B
Repeat computed tomography (CT) scan in $6$ months
Surgical excisionAnswer
D
Positron emission tomography (PET) scan
E
Image-guided core needle biopsy

Answer

Surgical excision

The CT findings describe a Bosniak Category IV complex renal cyst, which is characterized by thick, irregular septations and enhancing mural nodules or solid components. These features are highly predictive of cystic renal cell carcinoma (RCC). The standard of care for Bosniak III and IV cysts is definitive surgical excision (typically partial or radical nephrectomy), as they carry a high probability of malignancy. Proceeding directly to surgery is the most appropriate management step based on these imaging findings.

Step-by-Step Solution

Identify the primary clinical problem to be managed based on the question prompt.

The prompt asks for the management of the incidental

4.5\text{-cm}

right renal mass, not the symptomatic left ureteral stone.

Focusing on the specific question ensures the correct management algorithm is applied to the appropriate finding.

Interpret the specific imaging findings of the renal mass on the contrast-enhanced CT.

The mass is a complex cyst with thick, irregular septations and enhancing soft-tissue mural nodules.

These specific features classify the mass as a Bosniak Category IV cyst.

Determine the standard of care for the identified category of renal cyst.

Bosniak Category IV cysts carry a very high probability (

>90\%

) of being cystic renal cell carcinoma (RCC) and require direct surgical excision.

Definitive surgical treatment (partial or radical nephrectomy) is curative and avoids the false-negative risks associated with biopsying cystic lesions.

Key Concept

Bosniak classification of renal cysts and the indication for surgical excision in highly complex (Category IV) cysts.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic