Laparoscopic Nephroureterectomy with Heminephrectomy for Urothelial Carcinoma of the Upper Renal Pelvis on the Left Side of the Horseshoe Kidney

A 70-year-old male was diagnosed with urothelial carcinoma of the upper renal pelvis on the left side of the horseshoe kidney. Preoperative thin-slice contrast-enhanced CT with three-dimensional reconstruction of the images revealed that two arteries arising from the aorta supplied the left moiety of the horseshoe kidney. He underwent laparoscopic transperitoneal nephroureterectomy with heminephrectomy on the left side of the horseshoe kidney visualized by indocyanine green fluorescence system. The histopathological findings of the renal pelvic tumor revealed invasive urothelial carcinoma with squamous differentiation, high grade, and pT3.


Introduction
Upper tract urothelial carcinoma represents a small proportion (5%-10%) of all urothelial cancers [1]. Horseshoe kidney is a congenital abnormality in which the two kidneys are fused at their lower poles by a region of parenchymal and fibrous tissue called the isthmus [2]. There is no known association of horseshoe kidney with urothelial cancer; however, there are several case reports describing surgical management of tumors in patients with horseshoe kidney [3][4][5][6][7]. Herein, we present a case of urothelial carcinoma in the left renal pelvis of the horseshoe kidney. The patient underwent laparoscopic left nephroureterectomy with heminephrectomy for urothelial carcinoma of the upper renal pelvis on the left side of the horseshoe kidney.

Case Report
The patient, a 70-year-old male, was treated with laparoscopic radical prostatectomy and salvage radiotherapy for localized prostate cancer in 2016 and 2017.
Atypical urothelial cells were found in urine cytology in 2019 on a prostate cancer follow-up. There was no evidence of urothelial cancer on repeated computed tomography (CT) and cystoscopy; however, atypical urothelial cells in urine cytology continued to be detected. In May 2021, CT and magnetic resonance image (MRI) revealed a mass lesion of the upper pelvis of the left side of the horseshoe kidney (Figures 1(a) and 1(b)). A urine sample collected from the left side of the renal pelvis was suspicious for high-grade urothelial carcinoma in cytology. Thus, he was diagnosed with urothelial carcinoma of the upper renal pelvis on the left side of the horseshoe kidney. Preoperative thin-slice contrast-enhanced CT was performed with reconstruction of three-dimensional analysis of the images (SYNAPSE  3 Case Reports in Urology abdominal space. The operating time was six hours 21 minutes and estimated total blood loss was 250 ml. No postoperative complication occurred. (Figure 3). The excised organ revealed the tumor was a 30 × 15 mm mass in the upper renal pelvis. The histopathological findings of the renal pelvic tumor revealed invasive urothelial carcinoma with squamous differentiation, high grade, and pT3.

Pathological Findings
He was discharged from the hospital on postoperative four days. In February 2022, there was no evidence of recurrence.

Discussion
Horseshoe kidney represents one of the most frequent renal malformations, with an incidence of 0.25% among the general population, being twice as frequent in males [2]. The fusion prevents normal rotation of the kidney so that the ureter arises anteriorly and crosses over the isthmus.
It has been reported that the incidence of carcinoma of the renal pelvis is at least three times greater in horseshoe kidney patients [3]. The higher incidence has been attributed to chronic noxious stimulation associated with infection, stasis, and stones; however, the pathological features are unclear. Mizusawa et al. reviewed 24 cases of renal pelvic tumor in horseshoe kidneys previously reported in Japan [8]. Seven cases (30%) included components of squamous cell carcinoma. The renal pelvic tumor of the present patient also showed invasive high-grade urothelial carcinoma with squamous differentiation. Voided urine cytology performances are worse for upper urinary tract urothelial carcinoma than for urothelial carcinoma of bladder [1]. Because of its low sensitivity, urine samples are collected from the upper urinary tracts before injection of contrast medium for retrograde pyelography.
Variable blood supply is one of the anatomical features of horseshoe kidney. Majos et al. reported that horseshoe kidneys had nearly twice as many renal arteries as normal kidneys (4.57 vs. 2.4 per patient) [9]. Preoperative thinslice contrast-enhanced CT with reconstruction of threedimensional analysis of the images is extremely useful for detailed analysis of blood supply. We used a threedimensional analyzer of the images. Intraoperative ICG fluorescence navigation system is used for laparoscopic partial nephrectomy to conserve more normal renal tissue without increasing the rate of positive surgical margins [10]. Moreover, we revealed that blood flow evaluation by ICG system is also useful for performing laparoscopic heminephrectomy for a horseshoe kidney. We have not been detected previously published case reports of upper urinary tract cancer arising from horseshoe kidney treated with laparoscopic nephroureterectomy with 3D-reconstructed images or intraoperative ICG fluorescence navigation system.