‘ <scp> <i>BJUI</i> </scp> Clinical Dilemma’: the incidental small renal mass in a solitary kidney

Abstract

The incidental small renal mass (SRM; ≤4 cm; clinical T stage [cT]1a) has become increasingly common due to the widespread utilisation of ultrasonography and cross-sectional imaging. Today, most such patients present with asymptomatic, localised disease that can be surgically treated with curative intent; however, up to 25% of SRMs are benign [1]. This creates a clinical dilemma: balancing the removal of malignant tumours with avoiding needless active treatment for benign masses. This ‘BJUI Clinical Dilemma’ presents a structured format to address the common clinical presentation of a SRM through a case vignette approach. Following the vignette, leading experts will provide brief commentary, explaining the rationale behind their preferred management strategies. This approach encourages a balanced, expert-driven discussion on alternative strategies, offering readers insights into decision-making processes for common, yet nuanced cases in urological practice. A 63-year-old man presented to his primary care physician with an incidental CT finding of a 2.9-cm left renal mass in a congenital solitary left kidney, something the patient was previously unaware of, as part of an emergency room evaluation for brief epigastric pain—now completely resolved. He is an unmarried schoolteacher. He is overweight (body mass index of 29.7 kg/m2) and has well-controlled hypertension (on atenolol). He denies any history of smoking or occupational exposures and has no relevant family history. He denies any urinary symptoms, haematuria, flank pain, weight loss, or constitutional symptoms. His blood pressure is within the normal range, and physical examination reveals moderate central abdominal adiposity without any palpable masses or surgical scars. A full blood count and comprehensive metabolic panel are normal; urine analysis is unremarkable. Creatinine is 88 μmol/L and estimated GFR (eGFR) is 75 mL/min/1.73 m2. A contrast-enhanced CT scan was performed, including images without and with contrast during the arterial phase, revealing a 2.9 × 2.7 cm enhancing, exophytic renal mass arising from the posterior interpolar region of the left kidney (Radius, Exophytic/Endophytic, Nearness to collecting system or sinus, Anterior/Posterior, Location [R.E.N.A.L.] nephrometry score 8; Fig. 1). The mass briskly enhances, is well-defined, and appears to be predominantly solid. There are no signs of sinus, renal vein or perinephric fat invasion and no enlarged regional lymph nodes. The contralateral kidney is absent. A diagnostic chest X-ray was unremarkable. The patient seeks your opinion as to what would be his best course of action. This is a complex clinical scenario requiring individualised care, ideally delivered at a referral centre by an experienced multidisciplinary team (MDT). The case has many interconnected decision-points (Table 1) [2, 3]. Open vs laparoscopic vs robot-assisted PN Enucleation vs margin resection Cryoablation Microwave RFA The CT characteristics of the mass raise suspicion for RCC. While biomarkers are not integrated into routine diagnostic pathways for suspicious SRM [4], knowledge of the histology may improve risk-stratification and counselling. In this case, RMB appears safe and feasible and should be discussed with the patient. Yet, concerns about its feasibility, morbidity, and accuracy (especially in the WHO 2022 era) could limit its clinical value [5]. Likewise, novel promising ‘virtual biopsy’ tools are not yet ready for prime time and could paradoxically jeopardise decision-making [6]. To improve pre-treatment risk stratification, renal scintigraphy and potentially a nephrological consultation could be of value [2, 7]. Treatment options other than surgery could have specific drawbacks in this case. Active surveillance (AS) with potential delayed intervention is safe in carefully selected patients with a SRM [3] and should be transparently discussed. Yet, in this case—a patient with a low comorbidity burden, no red flags for