Congenital mid-ureteral stricture: a case report of two patients

Congenital ureteral stricture is a rare cause of paediatric hydronephrosis [1]. Congenital mid-ureteral stricture (CMS) is associated with severe hydronephrosis and proximal ureteral dilatation [2, 3]. However, this condition is typically diagnosed intra-operatively [3]. Here, we report two cases of CMS that were managed at our institute.

Mid-ureteral stricture is not a common cause of congenital hydronephrosis and is much less frequent than proximal or distal stricture [3]. Campbell published an autopsy series of 12 thousnads children. He found congenital ureteral obstruction in 1:150 autposies. Only 4% of them had a mid-ureteral obstruction. This outlines the rarity of CMS as a cause of congenital hydronephrosis [4].

Many theories have attempted to attribute stricture formation during embryogenesis to various causes, including a localized area of developmental arrest caused by extrinsic compression by foetal vessels during intrauterine life, a congenital ureteral valve, intrauterine ureteritis, and incomplete recanalization of the ureter [1, 5‐8]. However, the exact explanation remains unclear. Mid-ureteral stricture may appear as a definite stricture or as a true valve without lumen stenosis [9]. The cases described here involved definite lumen stenosis, and no valves were detected.

CMS may be associated with other congenital renal anomalies, including crossed renal ectopia [2], multicystic dysplastic contralateral kidney [8, 10], solitary kidney [11], contralateral blind ending ureter [11, 12], and ectopic ureter of a duplex system [13]. However, our current cases exhibited no congenital renal anomalies other than ureteral stricture. CMS is mostly diagnosed as a unilateral disorder; however, cases with bilateral anomalies have been reported in the literature [14]. Our cases involved CMS on one side with an apparently normal contralateral side.

CMS is typically not diagnosed preoperatively, and definite diagnoses have been reached via retrograde assessment of the ureter [3, 14]. Burgnara et al. reported one case of CMS diagnosed using foetal MRI in which prenatal ultrasound showed progressive left hydronephrosis with suspected proximal left ureteral dilatation; this diagnosis was confirmed postnatally by intraoperative RGP [15]. RGP remains controversial as a routine preoperative imaging procedure in cases of congenital hydronephrosis. Routine preoperative RGP is recommended in cases involving a diagnosis of an unexpected ureteral lesion, such as mid-ureteral stricture, ureteral polyp and retrocaval ureter. In addition to confirming this diagnosis, RGP will allow for the proposed surgical intervention to be performed without requiring extension of the incision or anastomosis with inappropriate exposure [8]. For this reason, Hawang et al. recommended routine RGP prior to repair, during the same anaesthesia session, unless the ureter distal to the point of obstruction has been well visualized by other means [3]. Conversely, Rushton et al. did not recommend routine RGP based on findings from 108 pyeloplasties performed between 1986 and 1992, and they also found that RGP was not necessary for successful repair [16]. Both of the patients described in the present report were initially diagnosed using RGP. RGP was helpful for not only assessing stricture size and length but also ensuring appropriate decision making. We recommend routine preoperative RGP to avoid operator errors during ultrasound and the exclusion of unexpected ureteral lesions.

In our institution, postoperative renogram is only indicated if deterioration of hydronephrosis is observed in any of postoperative ultrasound scans or there is a poor renal function preoperatively. Both cases had improved hydronephrosis in consecutive postoperative renal ultrasound scans; thus, postoperative renal scan was no indicated. Moreover, the preoperative DRF of our included renal units was acceptable.

The management of CMS involves resection of the stricture and re-anastomosis of the ureter, with no role for conservative management [3]. Our definitive management, which was the same as that described in the literature, included resection of the stenotic area and re-anastomosis of the ureter. In our second case, this procedure was performed via transperitoneal laparoscopy.

In our cases, chronic inflammatory cells were predominant in the excised stricture segments. Hawang et al. reported the presence of inflammatory cells in the stenotic area, although these cells did not appear to be significant. In their study, they found asymmetry in the thickness of the muscularis mucosa with non-significan acute or chronic inflammation of the stenosed segement in some cases [3]. In our second case, sever chronic inflmmation was clearly observed and there was a focal inflammation in case 1. This may refelct the role of inflammation in some cases of CMS.

Postoperative long-term follow-up revealed the regression of hydronephrosis. In most of the relevant literature, improvement in hydronephrosis and promising renal function have been reported during short-term follow-up [2, 10, 16].

CMS is a rare cause of congenital hydronephrosis that should be considered whenever proximal mega-ureter is an associated finding. Despite advanced radiological modalities, RGP remains the mainstay approach for diagnosing ureteral anomalies.