Case presentation and review of renal autotransplantation for nutcracker syndrome

Nutcracker Syndrome (NCS) is characterized by entrapment of the left renal vein, leading hematuria, flank pain, and proteinuria. We evaluated the efficacy of renal autotransplantation as a curative treatment for NCS through a review and case report. 55 patients from 18 studies were analyzed, with a combined 91% success rate of symptom resolution or improvement post-autotransplantation. In our case report, a 25-year-old man with severe NCS received laparoscopic nephrectomy and autotransplant, resulting in symptom resolution at 3.1 years follow up. Further research should confirm these findings and refine patient selection criteria and surgical techniques.


Introduction
Nutcracker syndrome is a rare condition characterized by the entrapment of the left renal vein (LRV) between the aorta and the superior mesenteric artery (SMA), resulting in distal dilation of the LRV. 1 It commonly presents with a classic triad of hematuria, flank pain, and proteinuria, but symptoms also include left varicocele and nonspecific gastrointestinal derangements such as nausea and loss of appetite. 2iagnosis is typically made through computed tomography (CT) or ultrasound demonstrating the "nutcracker phenomenon", with diagnostic thresholds ranging from >50 to 80% stenosis of the LRV accompanied by symptoms typical of this syndrome. 3Although NCS is rare, studies suggest ~23% of the population may have evidence of asymptomatic LRV compression on imaging. 4,5When symptomatic, pain associated with NCS can be debilitating and often necessitates therapeutic intervention.
The choice of treatment for nutcracker syndrome is based on the severity of the patient's symptoms.Conservative management is typically recommended for younger patients with mild to moderate symptoms.More invasive approaches include open, endovascular, and laparoscopic techniques, though there is no consensus on optimal treatment as data are limited. 6Endovascular approaches involve LRV stenting, with symptom resolution or improvement in >90% patients within 6 months but stent migration occurring in approximately 6.6%. 7,8Laparoscopic extravascular stent placement may be similarly efficacious with fewer complications. 9Open techniques include LRV transposition, nephropexy, gonadocaval bypass, and renal autotransplantation. 6 LRV transposition is most commonly employed, with favorable outcomes (>86% symptom resolution at 36 months) and few postoperative complications including ileus and retroperitoneal hematoma. 7Limited data exist on the efficacy of renal autotransplant, with most consisting of case series.Nevertheless, the procedure appears to effectively address both the issue of SMA-aortic compression and the challenge associated with the posterior position of the left kidney. 6ur study presents a literature review of renal autotransplantation for nutcracker syndrome and a case presentation of a patient with severe nutcracker syndrome who was successfully treated with renal autotransplantation.The goal of this study was to demonstrate that renal autotransplantation can be curative for carefully selected patients with nutcracker syndrome.

Case presentation
We present a case of a 25-year-old male patient with a history of Crohn's disease.Over a span of four months, the patient sought care at the emergency department on 14 separate occasions, each time presenting with symptoms of acute-on-chronic left flank pain, left testicular pain, and gross hematuria.
Diagnostic efforts, including a contrast-enhanced computed tomography (CT) scan of the abdomen, uncovered a notable entrapment of the left renal vein between the aorta and the superior mesenteric artery (SMA) before its entry into the inferior vena cava (IVC), as illustrated in Fig. 1.Further evaluation through renal venography and manometry solidified the diagnosis.
Given the complexity of the patient's condition, multiple treatment options were considered.Renal vein transposition and stenting were deemed unsuitable due to the high risk of stent migration.Moreover, attempts to alleviate symptoms through multiple nerve blocks directed at the celiac plexus and left splanchnic nerves did not yield successful outcomes.
The patient underwent a laparoscopic left nephrectomy followed by autotransplantation.During the laparoscopy, we observed a markedly engorged left renal vein accompanied by numerous surrounding varices, as depicted in Fig. 2. The left gonadal vein was subsequently ligated.
For educational purposes and to provide a comprehensive view of the procedure, surgical footage of the laparoscopic left nephrectomy described above has been made available: https://ucsf.box.com/s/78co95v5rmugydrfdhznwe55jod0an49 Following the thorough mobilization of the left kidney, it was extracted through a Pfannenstiel incision.The peritoneal cavity was then meticulously closed.The resected kidney was strategically placed within the right iliac fossa.An anastomosis was formed between the renal hilum and the right iliac arteries.Additionally, a refluxing ureteral implant was introduced into the dome of the bladder to ensure urinary continuity.
The patient's postoperative course was unremarkable, and his symptoms resolved following surgery (with latest follow up at 3.1 years post-operatively).
To compare our case with existing literature, we synthesized information on patient demographics, prior interventions, surgical techniques, complications, postoperative outcomes, and follow-up durations from studies published on renal autotransplantation for nutcracker syndrome.The aggregated data are presented in Table 1.

Discussion
Our study aimed to evaluate the effectiveness of renal autotransplantation as a curative treatment for nutcracker syndrome through a review of the literature and case presentation.We included 18 studies reporting on a total of 55 patients in our literature review.Overall, renal autotransplant was associated with favorable clinical outcomes (91% symptoms resolved or improved) and few complications.These results suggest that renal autotransplantation may be a viable option for carefully selected patients with nutcracker syndrome, especially those with severe symptoms or those who have failed or are not candidates for other treatments.However, it should be noted that further studies are needed to confirm these findings and to determine optimal patient selection criteria and surgical technique.
The pathophysiology of nutcracker syndrome (NCS) is not fully understood.Decreased perirenal fat and posterior renal ptosis with stretching of the left renal vein (LRV) over the aorta have been suggested as contributing factors. 10,11Recent studies have shown that abnormal branching of the superior mesenteric artery (SMA) from the aorta may also be a factor, resulting in compression of the LRV. 12 Intermittent hematuria and left-sided varicocele are the most common clinical manifestations of NCS, with several proposed mechanisms for hematuria, including rupture of thin-walled septum between hypertensive small veins and the collecting system. 13enal autotransplantation is a viable alternative for patients with NCS who are not candidates for endovascular intervention or LRV transposition, who wish to avoid the potential complications of endovascular stenting, or in those who desire a more definitive cure.In our review, two Clavien-Dindo grade 3 complications occurred, including torsion of the vascular pedicle leading to loss of the transplanted kidney and chylous ascites requiring percutaneous drainage.The authors noted that the former complication likely arose from intraperitoneal kidney placement and suggested retroperitoneal placement to reduce the risk of torsion. 14No studies have been conducted to determine the optimal surgical approach for renal autotransplantation, likely due to considerations such as patient expectations, physician experience, and institutional resources.
Campsen et al. ( 2021) 15 introduced an algorithm for classifying the severity of nutcracker syndrome and determining appropriate treatment.Severity is classified into four levels, with level 1 indicating asymptomatic patients with imaging findings only, level 2 with accompanying pelvic pain or congestion, level 3 with changes on renal venogram (pressures >2 mmHg and gonadal vein enlargement with  Our study has limitations that should be acknowledged.Firstly, we only included 18 studies reporting on 55 total patients, which may limit generalizability of our findings.Additionally, there was variability in

Fig. 1 .
Fig. 1.Contrast-enhanced computed tomography (CT) and renal venography showing entrapment of the left renal vein (LRV) between the aorta and superior mesenteric artery (SMA) prior to its insertion to the inferior vena cava (IVC).

Table 1
Summary of previously published studies on renal autotransplantation for nutcracker syndrome.