Spontaneous resolution of a 10 cm heterogenous renal lesion upon expectant management.

We describe a case of a patient with a large and clinically worrisome cystic renal lesion. Despite concerning imaging features, lack of definitive enhancement on cross-sectional imaging prompted a recommendation for expected management. The unusual lesion steadily decreased in size until it nearly entirely involuted over two years of follow-up. This case highlights the importance of careful treatment calibration and adherence to established clinical principles in patients who presents with clinically concerning renal lesions that lack definitive enhancement.

Introduction

The Bosniak classification system was developed to objectify assessment and standardize reporting of cystic renal lesions. We present a case of a patient with a ∼10cm Bosniak IIF versus III heterogenous cystic renal lesion that resolved spontaneously on close active surveillance. This case highlights prudence of established management principles of renal lesions.

Case presentation

A 69-year-old male presented to our institution for a second opinion regarding management of a left renal lesion that was found on evaluation of left flank pain. Initial computed tomography (CT) urogram demonstrated an obstructing 1.2 centimeter (cm) left distal ureteral calculus and a heterogeneous 9.9 cm left Bosniak IIF versus III complex heterogeneous cystic renal lesion with the R.E.N.A.L. Nephrometry score of 3 + 2+3 + x+3 = 11x in the interpolar region of the left renal unit. Although the lesion contained hyperdense components, no definitive enhancement could be documented (Fig. 1). At the time of endoscopic management of the left distal ureteral calculus, the patient had undergone a left pyeloscopy that did not demonstrate any evidence of urothelial carcinoma neither visually nor on cytological assessment. Three months following ureteral stone treatment, magnetic resonance imaging with and without gadolinium demonstrated a marked reduction in the size of the lesion to 5.4 cm, and, again, no definitive enhancement was noted. At this point, several opinions at outside institutions recommended that the patient undergo surgical resection.

Fig. 1

(A) An axial non-contrast CT image of complex cystic renal lesion with corresponding Houndsfield Units: 1 = 66 HU, 2 = 5 HU; (B) An axial contrast-enhanced CT image of complex cystic renal lesion with corresponding Houndsfield Units: 1 = 70 HU, 2 = 13 HU.

Given the lack of definitive enhancement, unremarkable endoscopic evaluation, and decrease in size of the renal lesion over a three-month interval combined with a history of ureteral obstruction, our team counselled the patient extensively and recommended expectant management with close surveillance. Repeat CT urogram 6 months after initial presentation revealed that the left renal lesion further decreased in size and now measured 2.2 cm without enhancement. Serial CT urograms obtained over a two-year period demonstrated that the lesion continued to decrease in size until it largely fully involuted (Fig. 2).

Fig. 2

A contrast-enhanced CT image demonstrating the decrease in size of renal cystic lesion after two years of active surveillance.

Discussion

We report a case of a patient with a renal lesion consistent with features of a Bosniak IIF versus III cyst, diagnosed concurrently with ureteral obstruction. Despite its complex heterogenous characteristics, we elected to closely monitor the lesion rather than proceed with surgical resection. The lesion steadily decreased in size until it involuted two years after initial presentation. We suspect that the cystic lesion may have been a calyceal diverticulum or a renal cyst with hemorrhage, precipitated by ureteral obstruction. There have been limited reports of renal cysts undergoing internal hemorrhage in the setting of ureteral obstruction., Furthermore, cases of calyceal diverticuli mimicking complex renal cysts on radiographic imaging have been described., As such, this case highlights importance of appropriate treatment intensity calibration in patients with equivocal renal lesions.

Conclusion

We report a case of a complex Bosniak IIF versus III cystic renal lesion without evidence of definitive enhancement that ultimately nearly fully involuted after two years of observation. This case underscores the importance of adherence to core management principles in order to avoid overtreatment of patients with renal mass.

Conflicts of interest

Matthew Lee, Ziho Lee, and Alexander Kutikov have no conflicts of interest or financial ties to disclose.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.