The occurrence of variations in the inferior vena cava (IVC) is uncommon in clinical practice (1), similarly, renal artery anomalies are also rare, and the coexistence of both anomalies is exceptionally unusual. The majority of patients with such anomalies display no discernible clinical symptoms or signs. Presently, the extensive utilization of imaging modalities, such as computed tomography (CT), facilitates precise preoperative diagnosis and minimizes the risk of intraoperative complications (2). In April 2024, our department managed a case involving a patient with a retrocaval ureter and right ureteropelvic junction obstruction. A detailed report of the case, accompanied by a review of pertinent literature, is presented below.

IVC, the largest vein in the human body, typically forms by the confluence of the left and right common iliac veins at the level of the fifth lumbar vertebra, with some variations converging at the fourth lumbar level. Variations in the IVC can generally be categorized into six types (1), including the absence of the hepatic segment, compensatory drainage of the superior vena cava via the azygos or hemiazygos veins; translocation of the IVC; double IVC malformation; ureter surrounding the IVC (retrocaval ureter); circumaortic left renal vein; and posterior aortic left renal vein. The retrocaval ureter, specifically, arises due to the development of the inferior renal vena cava from the right posterior main vein, causing the right ureter to traverse behind the IVC and descend to the right side of the abdominal aorta. This anomaly occurs in approximately 0.13% of the population (3). Although congenital, most patients remain asymptomatic (4) and are usually diagnosed between ages 30 and 40 (5). Bateson et al. (6) classified the retrocaval ureter into two types: Type I, the most common, features a fishhook, S-shape, or inverse J-shape configuration; and Type II, characterized by a sickle-shape with the upper ureter shifting to the midline at the pelvic level. In this case, CTU and Retrograde pyelography revealed typical fishhook-like changes in the ureter, confirming a Type I retrocaval ureter. Notably, the patient exhibited an uncommon presentation combined with IVC bifurcation malformation, where the IVC divided into left and right branches at L1 with the branches crossing at L3 (Figure 1).

UPJO refers to the obstruction of urine flow from the renal pelvis to the ureter, potentially leading to progressive kidney damage if undetected and untreated (7). UPJO affects approximately 0.05 to 0.13% of the population (8). Common causes include intraluminal ureteral stenosis, polyps, and valves; high ureteropelvic junction; dynamic dysfunction of the ureteropelvic junction; fibrous cord compression; and pressure from renal artery variations, which account for about 45% of cases (9). Renal artery variations can be categorized into two types: (1) Anterior renal artery branches, where those originating from the renal artery within 15 mm of its root are considered early branches (10); (2) Accessory renal arteries, where one kidney has more than one additional artery originating from the abdominal aorta or its branches (11). Reports indicate that accessory renal arteries occur in about 25.9% of cases, with those running on the ventral side of the pyeloureteral junction and directly into the inferior pole of the kidney occurring in about 6.3% (12), supplying 20 to 25% of renal parenchyma blood (13). The patient’s CTU showed that the right renal variant artery was an accessory renal artery originating from the abdominal aorta and merging transversely into the lower pole of the right kidney. This artery crossed the ventral side of the right ureteropelvic junction, causing compression and subsequent renal pelvis dilation (Figure 4).

Treatment for UPJO caused by ectopic blood vessels often requires tailored approaches based on the vessel’s location and direction. Common surgical methods for managing abnormal arteries include (14): (1) Vascular hitch procedure (for vessels located above the midline level of the kidney’s lower pole): The fibrous connective tissue on the ectopic vessel’s surface is clamped with 2–3 Hem-o-lok clips and fixed to the perirenal fat sac above the renal hilum. (2) Ectopic blood vessel transposition (for vessels below the midline level of the kidney’s lower pole): The kidney’s lower pole is exposed using an ultrasonic knife, and the ectopic vessel is carefully dissociated from its root, ensuring complete separation from the renal pelvis. After severing the ureter, the ectopic vessel is transposed to the dorsal side of the renal pelvis. If compression is still observed after anastomosis, the ectopic vessel can be fixed to the fascia of the psoas major muscle above the anastomosis to prevent recurrent compression of the anastomosis.

Based on a thorough analysis of the patient’s clinical data, we determined that the severe right hydronephrosis was attributed to a combination of retrocaval ureter and right ureteropelvic junction obstruction, necessitating simultaneous surgical intervention. Considering only a single stenosis cause could lead to its oversight during surgery, thereby failing to eliminate the obstruction comprehensively and adversely impacting the patient’s prognosis.

In a recent case report of retrocaval ureter (15), the surgeon employed traditional open surgery, with imaging data revealing a large incision and a restricted surgical field of view. Traditional open surgery is characterized by extensive trauma, longer incisions, prolonged postoperative recovery, and a higher incidence of complications. In contrast, laparoscopy provides the benefits of smaller incisions, faster postoperative recovery, decreased complications, as well as earlier mobilization and resumption of oral intake. Consequently, the patient underwent laparoscopic retrocaval ureteral realignment combined with right pyeloureteroplasty. During the procedure, ectopic vascular transposition was employed to address the anomaly in the right renal artery. The ureter was carefully dissected, and the red catheter was gently manipulated to safeguard the supporting blood vessels, while avoiding injury to the malformed inferior vena cava and misidentification of the right renal artery, which could potentially result in severe intraoperative complications like massive hemorrhage and partial renal ischemia or necrosis. Post-surgery, the patient exhibited satisfactory recovery.

Three months post-operation, the patient’s right renal hydronephrosis showed substantial improvement compared to the preoperative state. However, due to the prolonged duration of obstruction, morphological changes indicative of hydronephrosis persisted in the resected renal pelvis. Nevertheless, the patient’s renal function recovered remarkably. We will maintain rigorous follow-up and closely monitor any changes in renal pelvis morphology and renal function.

In summary, the coexistence of inferior vena cava and renal artery variations is uncommon in clinical practice, and their combined occurrence leading to hydronephrosis is even more rare. Comprehensive preoperative imaging assessments and meticulous film interpretation are crucial for the successful execution of the surgery. Laparoscopic retrocaval ureteral realignment, coupled with concurrent right pyeloureteroplasty, emerges as a safe, feasible, and effective therapeutic approach for managing this condition.