A case of mid‐ureteral stricture with ipsilateral atrophic kidney in a young adult

Introduction Most congenital ureteral strictures occur at the ureteropelvic or ureterovesical junction in children. Mid‐ureteral stricture is very rare and can cause congenital hydronephrosis. Only a few studies have reported on coexisting mid‐ureteral stricture with ipsilateral atrophic kidney in young adults. Case presentation A 16‐year‐old girl presented with repeated urinary tract infection. Computed tomography revealed a right atrophic kidney and hydroureter. Retrograde pyelography showed a mid‐ureteral stricture. Laparoscopic nephroureterectomy was performed, and histological examination revealed mid‐ureteral stricture with hyperplasia of the fibrous connective tissue and an atrophic kidney. Conclusion Mid‐ureteral stricture in a young adult is extremely rare. Appropriate imaging studies including retrograde pyelography are necessary for accurate diagnosis of mid‐ureteral stricture.


Introduction
Mid-ureteral stricture is very rare and can cause congenital hydronephrosis.We report a case of mid-ureteral stricture with an ipsilateral atrophic kidney, which required laparoscopic nephroureterectomy, in a young adult.

Case presentation
A 16-year-old girl was referred to our institute due to repeated UTI.She had mild right hydronephrosis from birth without VUR.Thereafter, she was observed regularly and followed up by pediatrics, who also recognized right atrophic kidney gradually.However, a detailed urinary tract examination had not been performed.Physical examination at our department revealed no obvious malformations in other organs.Laboratory findings were within normal limits (serum creatinine, 0.63 mg/dL), except for mild bacteriuria.Enhanced CT and MRI showed an atrophied kidney and dilated ureter on the right side (Fig. 1a,b).In particular, the right ureter appeared as a giant ureter on the sagittal section of MRU (Fig. 1c).Technetium-99m DTPA renal scintigraphy showed no accumulation in the right kidney.VCG showed no VUR.The right ureteral orifice was displaced in the midline of the bladder trigone, and no abnormal morphological findings of the orifice were found on cystoscopy (Fig. 2a).RP showed that the length of the mid-ureter stricture was about 10 mm.Although the urinary tract above the stricture was markedly expanded, the lower ureter below the stricture was not dilated (Fig. 2b).We performed a right nephroureterectomy with a diagnosis of mid-ureter stricture with an ipsilateral non-functional kidney.We tried to perform reduced-port laparoscopic surgery for cosmetic purposes.A GelPOINT access platform was placed between the tip of the 12th rib and the iliac crest.The renal artery and vein were ligated by retroperitoneal approach.As the ureter was markedly adherent to the surrounding tissue at the stricture, we added a 5cm incision in the right lower abdomen and extracted the right kidney and ureter (Fig. 2c).No abnormal blood vessels were found around the stricture site.Macroscopic findings revealed mid-ureter stricture and atrophic kidney (Fig. 3a).The lower ureter below the stricture did not dilate, similar to the findings on preoperative RP.Pathological examination findings confirmed that the mid-ureteral stricture was thickened due to hyperplasia of fibrous connective tissue and that the smooth muscle tissue and nerve fibers remained in place (Fig. 3b).Moreover, the muscular layer was maintained in ureteral dilatation, and mild inflammatory cell infiltration was observed (Fig. 3c).The renal tubules were almost completely atrophied, and glomeruli could not be identified.The patient was discharged without any notable perioperative events.Currently, 3 years have passed without a relapse of UTI.

Discussion
Most upper urinary tract obstruction lesions are commonly UPJO and UVJO, and stricture in the middle ureter is extremely rare.Congenital mid-ureter stricture is represented by a narrowing that occurs between the UPJ and UVJ.Campbell reported only 4% had mid-ureter stricture in an autopsy  of a sequence of 72 children who had ureteral stricture. 1ost recently, Meng et al. reported that middle ureteral stricture accounts for only 1.6% of all ureteral strictures. 2 Mid-ureteral stricture occurs at the level of the bifurcation of the common iliac vessels.Previous literature has shown that the ureteral lumen is shrunken by around 60% at the stricture site, resulting in a significant obstruction to urine delivery. 3Meng et al. reported that children with mid-ureteral stricture had relatively mild hydronephrosis and delayed onset of symptoms. 2Few studies have reported on mid-ureteral stricture diagnosed at 15 and 20 years of age. 4,5Hawang et al. reported that renal ultrasound and radionuclide renography alone do not suffice to identify the site of stricture, and that preoperative RP should be performed to identify the stricture site unless the distal ureter is well confirmed by other tests. 6If the distal ureter is not clearly visible or the diagnosis is unclear, MRU, CTU, or RP is performed to confirm the diagnosis.In our case, the hydronephrosis in childhood was mild, and the patient was followed up without a detailed examination of the ureter.We considered that midureter stricture causes repeated UTIs and severely atrophied kidney, resulting in renal function abolishment.
7][8][9] Previous review reported that congenital mid-ureter stricture is often associated with urological anomalies such as contralateral renal agenesis or atrophy, VUR, UPJO, solitary kidney, and ectopic ureteral opening.In our case, shifting of the ureteral orifice to the midline was observed.
In pathology, ureteral stricture is defined as a mechanical obstruction due to structural abnormalities in the wall.Two pathogenesis of ureteral stricture exist: ureteral valve and true ureteral stricture.The ureteral valve is a transverse fold of ureteral mucosa with anatomically proven. 5In our case, there was obvious luminal narrowing, but no valve was detected.Studies of the ultrastructure of ureteral stricture revealed that the stenotic ureter exhibits only quantitative changes in its composition.1][12] In our case, pathological examination revealed that the area of ureteral stricture was thickened due to hyperplasia of fibrous connective tissue and that the smooth muscle tissue and nerve fibers remained.The stricture site showed a low level of chronic inflammatory cell infiltration, which is consistent with findings reported in the literature.
General treatments for mid-ureteral stricture include excision of impaired passages and end-to-end anastomosis of the ureter.In adult cases, endoscopic procedures such as antegrade or retrograde endoureterotomy may be performed.In pediatric cases, endoscopic incision or dilation of the stenosis may be considered, but the success rate is lower than that of resection and anastomosis.Recently, treatment for ureteral stricture using laparoscopic and robotic technology is also available.Compared with open surgery, minimally invasive surgery has the advantages of less postoperative pain, shorter hospital stay, and less scarring.In the future, more patients will be able to undergo treatment with laparoscopic and robotic surgery.

Conclusion
We report a case of a young adult with mid-ureteral stricture with ipsilateral atrophic kidney, which required nephroureterectomy.A detailed image examination, including RP, is necessary for definitive diagnosis of mid-ureteral stricture.

Fig. 1
Fig. 1 Imaging findings.(a) Enhanced CT image shows the right atrophic kidney (yellow arrow) and hydroureter (pink arrow).(b) MRI shows right atrophic kidney (yellow arrow) and hydroureter (pink arrow).(c) MRU reveals marked hydroureter on the right side.

Fig. 2
Fig. 2 RP and intraoperative findings.(a) Cystoscopy shows that the right ureteral orifice is displaced to the midline of the bladder trigone.The illustration shows the location of the right orifice (red arrow).(b) RP reveals mid-ureter stricture (yellow arrow) and dilation of the upper ureter (pink dotted line).(c) Intraoperative image shows the mid-ureter stricture part without abnormal blood vessel crossing (yellow arrow).

Fig. 3
Fig. 3 Pathological examination findings.(a) Macroscopic findings show an atrophic kidney and extreme ureter dilation.Line-b is the stricture site, line-c is the dilatation site, and line-d is the atrophic kidney.(b) Pathological examination findings of the ureteral stricture site.The asterisk indicates the luminal side.Pathological examination findings reveal that the ureteral stricture is thickened due to hyperplasia of fibrous connective tissue (HE staining 920, EM 9 20).The smooth muscle tissue remains (desmin staining 920), and yellow arrows indicate that nerve fibers also remain (HE 9100).(c) Pathological examination findings at the ureteral dilatation reveal that the muscular layer is maintained, with mild inflammatory cell infiltration (HE 920).(d) Pathological examination findings of the kidney reveal that the renal tubules are almost completely atrophied, and glomeruli are not identified (HE 9100).