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Radiol Case Rep
Radiol Case Rep
Radiology Case Reports
1930-0433
Elsevier

S1930-0433(24)00841-0
10.1016/j.radcr.2024.08.058
Case Report
Retrocaval ureter presenting with hydronephrosis: A case report of rare entity in Nepal
Dhakal Saubhagya a
Jha Saroj Kumar jhasaroj13@gmail.com
b⁎
Adhikari Alisha c
Jha Pinky c
Katwal Srijana c
Poudel Dipesh a
a Department of Radiodiagnosis, National Academy of Medical Sciences, Kathmandu, Nepal
b Department of Radiodiagnosis, Tribhuvan University Teaching Hospital, Kathmandu, Nepal
c Department of Radiodiagnosis, Nepalese Army Institute of Health Sciences, Kathmandu, Nepal
⁎ Corresponding author. jhasaroj13@gmail.com
10 9 2024
12 2024
10 9 2024
19 12 57175723
24 7 2024
10 8 2024
12 8 2024
© 2024 The Authors. Published by Elsevier Inc. on behalf of University of Washington.
2024

https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Hydronephrosis, characterized by the dilation of the renal pelvis and calyces, often results from obstructive uropathy, commonly due to ureterolithiasis. However, rare congenital anomalies, such as a retrocaval ureter (RCU)-where the ureter passes behind the inferior vena cava- can also cause hydronephrosis. This case report describes an 11-year-old male presenting with right-sided flank pain and hematuria. Initial ultrasonography and noncontrast CT revealed right hydronephrosis without ureteral stones. Subsequently, contrast-enhanced CT urography found an abnormality in the course of the right ureter behind the inferior vena cava. He was diagnosed with right retrocaval ureter with hydronephrosis, and managed by surgical resection of the retrocaval segment and uretero-ureteral anastomosis. The postoperative course was uneventful. RCU usually presents in the third or fourth decade of life, however, it should be in the differential diagnosis of hydronephrosis in the pediatric population. The diagnosis of RCU is often delayed and missed till advanced imaging like CT urography is sought for unexplained hydronephrosis. If left untreated, it may lead to chronic renal failure. Therefore, emphasis should be placed on timely diagnosis and management of retrocaval ureter.

Keywords

Retrocaval ureter
Hydronephrosis
Ureterolithiasis
Congenital anomaly
CT urography
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pmcIntroduction

Hydronephrosis, characterized by the dilation of the renal pelvis and calyces, is commonly caused by obstructive uropathy, with ureterolithiasis being a frequent culprit. However, rare congenital anomalies, such as a retrocaval ureter-where the ureter passes posterior to the inferior vena cava (IVC)-can also lead to hydronephrosis [1]. The first recorded case of a retrocaval ureter was described by Hochstetter in 1893 [2]. Despite its rarity, a retrocaval ureter is a significant clinical entity due to its potential to cause urinary obstruction and associated complications. This condition is often discovered either incidentally or through various clinical manifestations primarily related to upper urinary tract obstruction and its complications [3]. To the best of our knowledge, no cases have been reported from Nepal. This case report aims to highlight the diagnostic process and the role of advanced imaging techniques in identifying this uncommon cause of hydronephrosis.

Case presentation

An 11-year-old male with no significant past medical history presented to the emergency department with right-sided flank pain and intermittent hematuria for 3 days. The pain was sharp, radiating to the groin, and not relieved by oral analgesics. He did not complain of fever, vomiting, or altered bowel habits. Physical examination revealed tenderness in the right costovertebral angle. Laboratory tests showed serum creatinine of 1.2 mg/dL (normal range: 0.7-1.3 mg/dL) and microscopic hematuria.

Initial ultrasonography demonstrated right-sided hydronephrosis with a suggestion of proximal ureteral dilatation. Noncontrast-enhanced computed tomography (CT) of the abdomen was performed to evaluate for ureterolithiasis. The CT scan confirmed right hydronephrosis but failed to identify a ureteral stone. Given the inconclusive CT findings, contrast-enhanced CT urography was performed. CT urography showed contrast pooling in the right pelvicalyceal system, indicating significant compression and hydronephrosis (Fig. 1). The right proximal ureter was dilated, with an abrupt medial deviation at the third lumbar vertebra, forming a characteristic S- or fish-hook shape (Fig. 2). The ureter's retrocaval course, observed in front of the L4 vertebral body in the right paramedian location before re-emerging anteriorly to reach the bladder, confirmed the diagnosis of a right retrocaval ureter, leading to hydronephrosis and hydroureter (Fig. 3).Fig. 1 Three-dimensional intravenous urography image at delayed phase shows pooling of contrast in the right pelvi-calyceal system with crossing of the ureter medially at L4 level. Also, the retrocaval course of ureter can be seen infront of the L4 vertebral body in the right paramedian location. The left course of the ureter is not fully visualized because of the easy passage of contrast into the urinary bladder.

Fig 1

Fig. 2 Multiplanar reformation CT urography image shows medial course of the right ureter crossing after crossing the inferior vena cava.

Fig 2

Fig. 3 Multiplanar reformation (MPR) image shows the course of the right ureter behind the inferior venacava. The retrocaval segment is compressed leading to proximal hydronephrosis.

Fig 3

The patient was then referred to a urologist for further management. Given the severity of the obstruction and hydronephrosis, surgical intervention was deemed necessary. The patient underwent open ureterolysis with resection of the retrocaval segment and uretero-ureteral anastomosis, restoring normal ureteral anatomy and function. Histopathologic examination of the resected segment showed chronic inflammation and fibrosis.

The patient had an uneventful postoperative recovery. Follow-up imaging at 3 months postsurgery showed resolution of hydronephrosis and a normally functioning right kidney (Figs. 4 and 5). The patient remained asymptomatic with normal renal function.Fig. 4 Coronal CT IVU delayed phase images showing decompression of the right pelvicalyceal system after treatment.

Fig 4

Fig. 5 Axial CT IVU delayed phase images showing decompression of pelvicalyceal system.

Fig 5

Discussion

The retrocaval ureter, also known as the preureteral vena cava or circumcaval ureter, is a rare congenital anomaly where the ureter passes posterior to the inferior vena cava (IVC) due to abnormal development of the IVC [4,5]. Maternal exposure to diethylene glycol monomethyl ether, an industrial solvent, during the fetal period is proposed as a probable cause [6]. This anomaly arises from the persistence of the right subcardinal vein as the renal segment of the IVC instead of the right posterior cardinal vein, which normally lies lateral to the ureter during weeks 4-8 of intrauterine development [7]. Typically, the IVC originates from the supracardinal and subcardinal veins inferior and superior to the kidney, respectively. If the subcardinal vein persists as the renal segment of the IVC, the IVC is positioned anterior to the ureter, leading to a retrocaval ureter [7]. In this condition, the proximal ureter crosses posterior to the IVC at the level of the third lumbar vertebra [5]. The term “preureteral vena cava” highlights the vascular origin of this condition [1].

The prevalence of retrocaval ureter is reported to be approximately 1 in 1000 [6] to 1 in 1100 live births [8], with an incidence range of 0.06%-0.17% worldwide [9]. Most cases are diagnosed postmortem during autopsies, with incidence varying between 1 in 1500 and 2 in 1000 cases [1]. The anomaly is typically observed on the right side in most patients [10], but it can occasionally be left-sided in cases such as situs inversus or IVC duplication [6]. The condition exhibits a strong male predominance, with a male-to-female ratio of approximately 2.8:1 [9,11]. Consistent with this, our case also involved a male with an affected right ureter.

Retrocaval ureter can be classified into 2 main types based on radiological and clinical features. Type 1 (Low Loop Type) is the more common variant, accounting for about 90% of cases. It features a ureter that crosses behind the IVC at the level of the L3 vertebra and forms an S- or fishhook-shaped deformity on imaging. Type 1 retrocaval ureter is often associated with moderate to severe hydronephrosis due to significant medial displacement of the ureter and obstruction, leading to marked dilation of the upper urinary tract proximal to the obstruction site. Type 2 (High Loop Type) is a less common variant, accounting for about 10% of cases. It features a ureter that crosses behind the IVC at the level of the renal pelvis, forming a smooth, sickle-shaped curve. Type 2 is typically associated with mild hydronephrosis and less severe obstruction. The ureter in this type lies horizontally, and the retrocaval segment is at the same level as the renal pelvis, often resulting in less pronounced urinary tract dilation [12]. Our patient had Type 1 retrocaval ureter.

Retrocaval ureter may be asymptomatic and discovered incidentally during radiological imaging for other problems [11]. However, patients often present with nonspecific symptoms that mimic other conditions like ureteropelvic junction obstruction (UPJO) or urinary stone disease. Despite being congenital, patients with retrocaval ureter generally present in their third or fourth decades of life when they develop symptoms such as dull, aching flank pain due to hydronephrosis or hydroureteronephrosis [13]. However, our case presented earlier, at 11 years of age. The main causes of hydronephrosis are lumen stenosis, torsion, and adhesion of the retrocaval segment. This segment is compressed by the psoas muscle, spinal column, and vena cava, leading to inflammation and fibrosis [14]. Approximately 80% of retrocaval ureter cases are symptomatic. The most common symptom is right flank pain, occurring in about 70% of cases [15]. Other symptoms include hematuria, present in about 20% of cases, which can be isolated or associated with flank pain and often related to urolithiasis [9]. Additional symptoms may include urinary tract infections (UTIs) [3], hematuria, and, in some cases, hypertension [6].

Other disorders associated with retrocaval ureter include retroperitoneal fibrosis, carcinoma of the ureter, and renovascular hypertension [16]. The condition may also be linked with cardiovascular and urogenital anomalies, such as kidney agenesis [10], horseshoe kidney, ureteropelvic junction obstruction, Turner's syndrome, esophageal atresia, congenital absence of the vas deferens, hypospadias [17], syndactyly in both feet, intestinal malrotation, and Goldenhar syndrome [18]. Therefore, all patients with retrocaval ureter should be screened for these disorders [10].

Different diagnostic modalities, including intravenous pyelography, RP, inferior vena cavagraphy, abdominal sonography, abdominal CT, and MRI, have been utilized [18]. While abdominal ultrasound can demonstrate hydronephrosis and proximal hydroureter, its ability to delineate the ureter is limited. It is primarily used for initial screening and follow-up in patients with suspected or known retrocaval ureter [7,15]. Historically, several diagnostic methods were used, but contemporary practices favor less invasive and more precise imaging techniques such as computed tomography (CT) scans and magnetic resonance imaging (MRI). Spiral CT scans have become the preferred method for diagnosing retrocaval ureter due to their ability to delineate both the ureter and IVC accurately [1,13]. The presence of the vena cava lateral to the right pedicle of the third lumbar vertebra, seen in 94% of patients with circumcaval ureter and only 6% of normal individuals, is said to be the pathognomonic feature of circumcaval ureter on CT [17]. CT urography (CTU) is particularly valuable as it offers a comprehensive evaluation, revealing the ureter's abnormal dorsal position, the exact level at which it deviates medially, and the extent of compression by the aberrant vessel. CTU also provides information on the degree of pelvicalyceal system dilatation proximal to the obstruction and the kidney's excretory function. This makes CTU a “one-stop-shop” for assessing retrocaval ureter and planning surgical intervention if necessary [9,15,19]. MRI is equally effective as CT in diagnosing retrocaval ureter and has the added advantage of not exposing patients to radiation [1,8]. It is particularly beneficial for patients with poor renal function, pregnant women, and children [17].

Management of retrocaval ureter typically depends on the severity of symptoms and the degree of hydronephrosis. Asymptomatic patients or those with mild hydronephrosis may only require periodic monitoring [4,6,20]. When surgery is required, the primary goal is to relieve the obstruction and restore normal urinary flow. The technique usually used is ureteral uncrossing with restoration of continuity of the excretory pathway by direct plasty and end-to-end uretero-ureteral anastomosis in Type 2, and resection-anastomosis of the retrocaval segment in Type 1 [3,8]. This can be done through open surgery or minimally invasive techniques such as laparoscopic or retroperitoneoscopic surgery. Laparoscopic approaches are often preferred due to their benefits, including less blood loss, shorter hospital stays, reduced postoperative pain, and better cosmetic results [15,18]. Various surgical techniques are available, and the choice of procedure is guided by the clinical presentation and specific anatomical features of the ureter and IVC in each patient [10,14,15]. Postoperative care includes the placement of a double-J stent to ensure proper drainage and healing of the ureter. Regular follow-up with imaging studies is crucial to monitor the success of the surgery and detect any potential complications [5,9]. Early diagnosis and appropriate surgical management are crucial to prevent irreversible renal damage, particularly in symptomatic patients [20].

Conclusion

Retrocaval ureter, though rare, should be included in the differential diagnosis of unexplained hydronephrosis, particularly when initial imaging does not indicate more common causes such as ureterolithiasis. Though it generally presents in third or fourth decade, it can occur in pediatric age group as well. Increased awareness and the use of advanced imaging techniques like CT urography are essential for accurate diagnosis. Early detection and surgical intervention can prevent long-term complications like chronic renal failure.

Authors contributions

Authors 1, 2, 6—Led data collection, and contributed to writing the case information.

Authors 1, 2, 3—Contributed to the process of original draft preparation and introduction and discussion.

Authors 2, 3, 4, 5—Contributed to conceptualization and discussion.

Author 1, 2, 3, 4, 5—Revised it critically for important intellectual content, and contributed in review and editing.

Author 2, 3—Edited the rough draft into the final manuscript.

Provenance and peer review

Not commissioned, externally peer reviewed.

Patient consent

Written informed consent was taken from the patient for the publication of the case report and the images. A copy of it is available for review by the editor-in-chief of this journal on request.

Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments: None.
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