Asymptomatic Obstructive Ureterolithiasis Due to a Periureteral Venous Ring

Abstract

Background: Periureteral venous rings are a rare congenital anomaly involving the inferior vena cava (IVC) and the right ureter, where the ureter courses through a venous ring made by the duplication of the IVC during embryogenesis. This anatomic anomaly is also referred to as a transcaval ureter. Although most patients are asymptomatic and radiographic findings are incidental, some patients can be symptomatic. We present the first reported case of asymptomatic obstructive ureterolithiasis at the level of a periureteral venous ring that was effectively treated with endoscopic management.

Case Presentation: A 47-year-old woman was found to have right hydroureteronephrosis on MRI. Further CT imaging showed an obstructing ureteral stone at the level of a periureteral venous ring. After initial decompression with ureteral stenting, she underwent ureteroscopy that revealed the ureteral stone at the level of the venous anomaly. The stone was fragmented and removed with laser lithotripsy and stone basket manipulation. After a period of ureteral stenting and removal, she had improved hydroureteronephrosis, no symptoms of ureteral obstruction, and stable renal function. Given these findings, she elected for surveillance with imaging in lieu of any reconstructive procedure to transpose the ureter around the venous anomaly.

Conclusions: We present the first reported case of obstructive ureterolithiasis at the level of a periureteral venous ring. Our experience suggests that, with preoperative ureteral stenting, obstructing ureteral stones in the setting of an IVC anomaly can be managed with retrograde flexible ureteroscopy. Conservative laser settings and minimal torqueing of the ureteroscope are advised given adjacent vascular anomaly. Cases wherein the affected ureteral segment is too constricted or tortuous to allow for stone passage or for ureteroscopy may require management by percutaneous antegrade intervention. Surgical reconstruction of the ureter should also be considered.

Introduction and Background

Periureteral venous ring is a rare congenital anomaly involving the inferior vena cava (IVC) and the right ureter, where the ureter courses through a venous ring made by the segmental duplication of the IVC during embryogenesis.¹ This anatomic anomaly is also referred to as a transcaval ureter; however, the variant is caused by an abnormality of the IVC, not the ureter itself.¹ Most patients are asymptomatic and radiographic findings are incidental. However, some patients have hydroureteronephrosis on imaging and are symptomatic with flank pain or recurrent urinary tract infections.² We present the first reported case of asymptomatic obstructive ureterolithiasis at the level of a periureteral venous ring with hydroureteronephrosis that was managed with ureteroscopy and laser lithotripsy.

Case Presentation

A 47-year-old woman presented to our clinic after referral for incidental right hydroureteronephrosis noted on MRI of the uterus during evaluation of menorrhagia. A follow-up CT scan of the abdomen and pelvis without intravenous (IV) contrast showed a dilated right ureter to the level of the uterine mass, which consisted of a large fibroid. A 5 mm calcification was noted within the proximal ureter at the level of an anomaly in the IVC (Fig. 1). The ureter was noted to be traversing through a bifurcation in the infrarenal portion of the IVC, a variant known as a periureteral venous ring or a transcaval ureter. This venous anomaly was confirmed on updated CT imaging with IV contrast and intravenous pyelography (Fig. 2). The patient denied a history of flank pain or other urologic complaints before the incidental findings. Urinalysis in the clinic was positive for blood but showed no signs of infection. Laboratory evaluation showed normal serum creatinine and estimated glomerular filtration rate.

FIG. 1.

CT abdomen and pelvis showing obstructing ureteral calculus at the level of the periureteral venous ring (identified by arrow). CT, computed tomography.

FIG. 2.

CT abdomen and pelvis with IV contrast and IV pyelography showing periureteral venous ring (anterior and posterior segments of IVC identified by arrows) with ureter (identified by outline and arrow). IV, intravenous; IVC, inferior vena cava.

The patient was taken to the operating room for cystoscopy, bilateral retrograde pyelograms (RPGs), right ureteroscopy, and ureteral stent placement. Cystoscopy and left RPG were unremarkable. Right RPG showed hydroureteronephrosis, specifically involving the proximal ureter to the level of the enlarged uterus. There was also proximal ureteral tortuosity with an associated ureteral filling defect consistent with previously observed ureteral stone at the level of the IVC anomaly (Fig. 3). A flexible ureteroscope could not be passed through the distal ureter because of apparent external ureteral compression from the uterus.

FIG. 3.

Retrograde pyelogram images showing periureteral venous ring (left image) and proximal ureteral filling defect consistent with known ureteral stone (right image).

As a part of a multidisciplinary plan for further management of her ureteral stone and large uterine fibroid, bilateral ureteral stents were placed to facilitate ureteral identification during her upcoming hysterectomy and to relieve her proximal right ureteral obstruction. She underwent total abdominal hysterectomy with gynecology without complication. She returned to clinic with updated CT imaging showing persistent right hydroureteronephrosis to the level of the IVC ring despite appropriate ureteral stent placement as well as a calcification along the ureteral stent consistent with known ureteral stone. She then underwent uncomplicated right flexible ureteroscopy with laser lithotripsy for the ureteral stone.

CT imaging was obtained at 1 month postoperatively and was notable for improved right hydroureteronephrosis. Stone analysis showed mixed calcium oxalate and calcium phosphate stone composition. Renal function remained normal and she continued to be asymptomatic, denying any flank pain or episodes of renal colic. Options for further management were discussed including surveillance vs surgical correction of the ureteral anomaly to prevent further episodes of ureterolithiasis at the IVC ring. Given her lack of symptoms and stable renal function, she elected to proceed with surveillance. She adopted dietary modifications and other general stone prevention techniques for management of her stone disease.

She remained asymptomatic at 4 months postoperatively and an updated retroperitoneal ultrasonography showed stable mild right caliectasis. She was again offered surgical reconstruction, but she declined and opted for continued surveillance with imaging.

Discussion and Literature Review

Periureteral venous rings are one of several congenital embryologic anomalies of the IVC.³ The infrahepatic IVC develops between the 6th—8th weeks of embryogenesis from continued appearance and regression of three paired embryonic veins: the posterior cardinal, subcardinal, and supracardinal veins.³ The normal IVC is composed of four segments: hepatic, suprarenal, renal, and infrarenal.² The hepatic segment is derived from the vitelline vein, the suprarenal segment is derived from the right subcardinal vein, the renal segment is derived from the right suprasubcardinal and postsubcardinal veins, and the infrarenal segment is thought to derive from the right supracardinal vein.³ Owing to the course of the embryonic ureter, which lies posterior to the posterior cardinal vein and anterolateral to the supracardinal vein, the ureter can become encircled with the formation of anastomoses between derivatives of these embryonic veins.³ Giddy et al. hypothesized that the periureteral venous ring represents a partial duplication of the infrarenal IVC formed from the lack of regression of the right posterior cardinal and right supracardinal veins at the level of the kidney.² Transcaval ureters are reported to have a prevalence around ∼1 in 1100 with a 2.8:1 male-to-female ratio.¹ It should be noted that transcaval ureters are caused by an anomaly of the IVC, not the ureter itself.¹

To our knowledge, this is the first reported case of asymptomatic obstructive urolithiasis caused by a ureteral stone at the level of a periureteral venous ring. Although our patient presented with distal ureteral obstruction concomitantly caused by external compression from a large uterine fibroid, her hydronephrosis persisted after hysterectomy, indicating that her periureteral venous ring was a true site of ureteral obstruction. External compression of her distal ureter caused by her enlarged uterus prevented the possibility of primary ureteroscopy for treatment of her stone before her planned hysterectomy.

Ureteral stenting in the interim allowed for ureteral dilation and eventual accommodation of the ureteroscope for definitive stone management. Flexible ureteroscopy was favored over semirigid ureteroscopy given known proximal ureteral tortuosity and concern for adjacent vascular structures at the level of the venous ring. Conservative laser parameters were utilized to minimize the chance of ureteral damage. Had her ureter and associated venous ring not accommodated a flexible ureteroscope for intervention, she would have likely required percutaneous antegrade flexible ureteroscopy with laser lithotripsy for ureteral stone removal. Percutaneous antegrade interventions have not been described in the setting of a transcaval ureter.

A case report by Bhatia et al. supports conservative management of nephrolithiasis secondary to a retrocaval ureter, a slightly different congenital embryologic anomaly of the IVC, with stenting and shockwave lithotripsy (SWL).⁴ They reported that preoperative ureteral stenting helped to change the shape of a retrocaval ureter that allowed for easier passage of stones broken up by SWL.⁴ In our patient, we hypothesize that urinary stasis at the level of the periureteral venous ring contributed to stone formation. Surgical correction of these ureteral anomalies should be considered to prevent similar episodes in the future. This typically consists of dismembered ureteral transposition around the venous anomaly, commonly accomplished through robotic or laparoscopic approach.² Indications for surgical correction typically include recurrent urinary tract infections, impaired renal function, or urolithiasis.³ Otherwise management can be conservative. Our patient remained asymptomatic with normal renal function and, therefore, elected for surveillance.

Conclusions

We present the first reported case of obstructive ureterolithiasis at the level of a periureteral venous ring. Our experience suggests that, with preoperative ureteral stenting, ureteral stones adjacent to IVC anomalies can be managed with retrograde flexible ureteroscopy and laser lithotripsy. Conservative laser settings and minimal torqueing of the ureteroscope are advised given adjacent vascular anomalies. Cases wherein the affected ureteral segment is too constricted or tortuous to allow for stone passage or for flexible retrograde ureteroscopy may require management by percutaneous approach. Surgical correction should also be considered to prevent future problems.

Abbreviations Used

CT

computed tomography

IV

intravenous

IVC

inferior vena cava

MRI

magnetic resonance imaging

RPGs

retrograde pyelograms

SWL

shockwave lithotripsy

Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Cite this article as: Rabley A, Singh D, Rawlings T, Bird V, Yeung L (2020) Asymptomatic obstructive ureterolithiasis due to a periureteral venous ring, Journal of Endourology Case Reports 6:4, 505–508, DOI: 10.1089/cren.2020.0176.