Percutaneous endoscopic resection of a large fibroepithelial polyp in the renal pelvis using a resectoscope: a case report

Introduction

Fibroepithelial polyps (FEPs) in the renal pelvis are benign tumors of the urinary tract, that originate from transitional epithelium of the urinary tract. FEPs in the renal pelvis are extremely rare, with less than 30 cases reported until 2021 (1). Li et al. reported the incidence of FEPs in the ureter in children (2); however, to our knowledge, no specific incidence of FEPs in the renal pelvis has been reported. Diagnosis before surgery is difficult because one cannot distinguish between FEPs and malignancies based on imaging data alone. Misdiagnosis leads to unnecessary and even radical treatment (3,4), which places unnecessary health and financial burden on patients. We present this case in accordance with the CARE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-24-434/rc).

Case presentation

In September 2023, a 36-year-old female patient presented to our hospital with a lesion occupying the left renal pelvis and hydronephrosis, which was revealed by a health examination. She had no gross hematuria or flank pain. Physical examination on admission revealed no obvious abnormalities. There were no obvious abnormalities in laboratory hematologic serological, and coagulation tests at admission. The patient was neither a habitual drinker nor a smoker, and had no remarkable medical or family history. Preliminary ultrasonography revealed the possibility of transitional cell carcinoma (TCC). Computed tomography urography (CTU) showed a large filling defects in the left renal pelvis with pretty smooth outline and slight enhancement, with hydronephrosis in the delayed stage (Figure 1A,1B). She underwent contrast enhancement magnetic resonance imaging (MRI) of the urinary system and magnetic resonance urography (MRU), which also indicated a filling defect with hydronephrosis (Figure 1C,1D). Both computed tomography (CT) and MRI findings indicated a high possibility of TCC. However, the urine cytology result suggested that there were no tumor cells.

Figure 1 Imaging finding of the mass. (A) Contrast-enhanced CT scan showed an occupying lesion of the left renal pelvis (red arrow). (B) CT on excretory stage showed a large filling defects in the left renal pelvis (red arrow). (C,D) Coronal CT and MRI findings of the polyp (red arrow). CT, computed tomography; MRI, magnetic resonance imaging; DFOV, display field of view.

The patient was pretty young compared to upper urinary tract urothelial carcinoma (UTUC) patient and had no typical symptoms of TCC, such as hematuria. The imaging findings were long strip shape with smooth profile, which is not typical of malignancy. Considering these factors, we decided to explore the urinary tract and biopsy the mass (Video 1). Smooth mucosa was observed under cystoscopy, and no stones or tumors were found. A polyp-like neoplasm with smooth surface, approximately 1 cm in diameter and 4 cm in length, was observed filling most of the left renal pelvis under a flexible ureteroscopy (FURS) (Figure 2A). The mass had a thin base and appeared to originate in the lower calyx of the left kidney. A thulium laser was used to cut the tip of the mass for biopsy (Figure 2B,2C). The biopsy tissue was large (8 mm in diameter). When we tried to pull it out with a basket, it was blocked in the upper ureter. We had to cut it into two halves. Histopathological examination revealed proliferative epithelial cells with formation of Brunn’s nest (5), which is a kind of benign urothelial lesion. Postoperatively, a ureteral stent and urethral catheter were inserted. After discussion with pathology and imaging department, the mass was considered to be a FEP in the renal pelvis. The mass was too large to be removed by FURS; therefore, we decided to perform percutaneous endoscopic resection with assistance of FURS. If the polyp could be pulled through the renal access, it could be resected en bloc with a thulium laser cutting the base, otherwise it could be resected with a resectoscope.

Figure 2 Ureteroscopic view (at the time of biopsy). (A) The polyp originated from renal pelvis and filled the upper ureter (red arrow). (B) Image of the mass after biopsy (red arrow). (C) The shape of the specimen, about 8 mm in length (red circle).

After general anesthesia administered, the patient was placed in the prone split-leg position. A ureteroscope was performed. The Double J (D-J) stent was removed. We then inserted a F12/14 ureteral access and F7.5 PUSEN flexible digital ureteroscope (PU3033A; Zhuhai Pusen Medical Technology Co., Ltd., Zhuhai, China). Inspection of the entire collecting system revealed the large polyp-like mass that had been detected in the previous FURS. Under the guidance of ultrasonography and ureteroscopy, the surgeon chose the 11^th intercostal skin puncture site to construct a F24 percutaneous renal access into the posterior mid-upper calyx with a F24 Bard X-Force N30 Nephrostomy Balloon Dilation Catheter (Bard Inc., Covington, Georgia, USA) (Figure 3A). The head of the polyp was grasped with a self-made thread loop with the nephroscope and witnessed by the FURS (Video 2, Figure 3B,3C). Unfortunately, the polyp was too large to be pulled into the F24 access. So, we decided to resect it using a F24 Olympus Resectoscope (Olympus Corporation, Kuehnstr., Hamburg, Germany), which may be called percutaneous nephrostomy resection of a pelvis tumor (PCNR-PT). The surgeon gradually removed the tumor from the tip to the base (Figure 3D,3E). Due to the large size of the tumor, the resection process took about 90 minutes, and intraoperative bleeding was less. An F6 26 cm DJ stent and F20 nephrostomy tube were indwelled (Video 3).

Figure 3 Images during the surgery. (A) Construction of the F24 percutaneous renal access. (B,C) Under the guidance of flexible ureteroscopy (white arrow), a self-made thread loop (red arrow) was used to wrap around the polyp (blue arrow). (D) The process of using resectoscope (white arrow) to resect the polyp. (E) The base of the polyp after resection (white arrow).

Postoperative pathology again verified a polyp containing epithelial cells, chronic inflammatory cells, proliferative smooth muscle cells, and small vessels (Figure 4). Immunohistochemical analyses revealed that CK20 and P53 were negative, and Her-2 was positive. No postoperative recurrences or complications were observed. After four months, the patient underwent a CT scan and a ureteroscopy. There were no signs of recurrence (Video 4, Figure 5).

Figure 4 Histological preparation of the polyp showing smooth muscle cell and small blood vessel hyperplasia, chronic inflammatory cell infiltration and Brunn’s nests (hematoxylin-eosin stain; ×100 lens magnification).

Figure 5 Postoperative presentation. (A) Anterograde urography showed no residual mass and Double J (D-J) stent was in position. (B) Flexible ureteroscopy showed smooth mucous membrane of left inferior calyx 4 months after operation, and no recurrence of polyps was observed.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images/videos. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

FEPs most often occur in adults aged between 30 and 40 years, pretty much younger than UTUC patients (6). The etiology is uncertain. Developmental defects, slow-growing congenital lesions, and acquired causes such as inflammation, calculi, or obstruction have been hypothesized (7). FEPs are extremely rare and can be found in the ureter, ureteropelvic junction, and renal pelvis. Among these sites, polyps that occur in the renal pelvis are much rarer.

The radiological differential diagnosis of FEPs in the renal pelvis includes blood clots, radiolucent calculi, and TCC (7). It is difficult to diagnose FEPs in the renal pelvis using radiography alone, as the imaging results are not specific. The most common imaging finding is a filling defect in the renal pelvis with enhancement in contrast-enhanced CT. Because of the similar radiologic findings, it is challenging to differentiate FEP from blood clots, and tumors (7,8). Urine cytology is routinely performed to evaluate for malignancy. However, these polyps are covered with normal urothelium; hence, urine cytology is often of limited use in distinguishing them from malignancies (9). These benign lesions are often mistaken for TCC, which results in unnecessary treatment. For these reasons, preoperative endoscopic examination is recommended to distinguish FEPs from other urinary tract tumors. Therefore, misdiagnoses that lead to unnecessary treatment, such as nephroureterectomy, can be avoided. In this case, she was young, had no hematuria or other symptoms, and her imaging findings were not typical, which made us suspect the nature of the lesion.

Treatment of FEPs of the renal pelvis includes open nephroureterectomy, open polypectomy with re-anastomosis, or endoscopic removal of polyps. In recent 20 years, there were 3 cases, of which one underwent percutaneous endoscopic resection (8), one underwent retrograde endoscopic resection (1), and one underwent radical nephroureterectomy (10). But the sizes of the FEPs in the previous two papers were not mentioned. In this case, we successfully resected a large FEP in the renal pelvis through a percutaneous approach. We used a F24 nephroscope balloon to establish the F24 access. The resectoscope can freely enter the F24 channel, and the renal pelvis can be kept slightly dilated under irrigation, which is conducive to observation, tumor resection and hemostasis. During the procedure, the irrigation speed should be carefully controlled within 50–100 mL per minute. To the best of our knowledge, this is the second report on the use of a resectoscope to remove FEP in the renal pelvis in the past 20 years.

Although there is no consensus on the duration and recommendations for postoperative follow-up, no recurrence was found during our follow-up period of 4 months.

Conclusions

FEP of the renal pelvis is a rare benign neoplasm for which a preoperative biopsy may be useful. The development of endoscopic technology makes preoperative diagnosis, treatment, and postoperative follow-up possible. We present the case of a 36-year-old woman, who successfully underwent percutaneous endoscopic resection of a large FEP in the renal pelvis by a resectoscope without recurrence or complications. The surgical technique is innovative and adds to the body of evidence for the successful endoscopic management of FEP. However, this technique requires more cases to confirm its effectiveness.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-24-434/rc

Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-24-434/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-24-434/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images/videos. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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