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Case Report

Vasc Specialist Int (2023) 39:13

Published online June 13, 2023 https://doi.org/10.5758/vsi.230036

Copyright © The Korean Society for Vascular Surgery.

Posterior Nutcracker Syndrome Caused by Abdominal Aortic Aneurysm: A Case Report

Chayatorn Chansakaow and Saranat Orrapin

Division of Vascular Surgery, Department of Surgery, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand

Correspondence to:Saranat Orrapin
Division of Vascular Surgery, Department of Surgery, Faculty of Medicine, Chiang Mai University, 110 Intawaroros Road, Si Phum, Muang, Chiang Mai 50200, Thailand
Tel: 66-53935532
Fax: 66-53936139
E-mail: O.saranat@gmail.com
https://orcid.org/0000-0001-5670-4566

Received: April 19, 2023; Revised: May 15, 2023; Accepted: May 28, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Posterior-type nutcracker syndrome (NCS) is a rare disease characterized by the compression of the left renal vein between the aorta and the vertebral body. The optimal management strategy for NCS remains a subject of debate, with surgical intervention being considered for selected patients. Here we report the case of a 68-year-old male who presented with a one-month history of abdominal and flank pain as well as hematuria. Abdominal computed tomography angiography revealed the compression of left renal vein between an abdominal aortic aneurysm (AAA) and the vertebral body. The patient was suspected to have a posterior-type NCS, which significantly improved following open surgical repair of the AAA. In cases of posterior-type NCS, surgical intervention should be performed selectively in symptomatic patients, and open surgery is the preferred treatment modality for this condition. For posterior-type NCS associated with AAA, open surgical repair may represent the optimal choice for decompression of the NCS.

Keywords: Renal nutcracker syndrome, Abdominal aortic aneurysm, Renal veins

INTRODUCTION

Nutcracker syndrome (NCS) or renal vein compression syndromes are rare conditions. A radiologic study revealed a prevalence of 10.9% for the nutcracker phenomenon during the evaluation of abdominal computed tomographic scans for other indications [1]. However, the exact prevalence of NCS, which represents the clinical equivalent of the nutcracker phenomenon and encompasses a complex range of symptoms with significant variation, remains unknown due to the lack of unified diagnostic criteria. NCS can be classified into two types [2]. The anterior-type is characterized by left renal vein entrapment between the superior mesenteric artery and the aorta. On the other hand, posterior-type NCS is very rare and involves the compression of the left renal vein between the aorta and the vertebral body [3-5]. We present a case of posterior-type NCS in a patient with an abdominal aortic aneurysm (AAA) that demonstrated improvement following AAA repair. Informed consent was obtained from the patient.

Institutional Review Board approval was waived due to the retrospective case report (SUR-25660152). It has been certified as exempt from ethical review by the Research Ethics Committee of Faculty of Medicine, Chiang Mai University.

CASE

A 68-year-old male presented with a one-month history of abdominal and flank pains that had worsened. His medical history included a cerebrovascular accident, hypertension, and dyslipidemia. Vital signs were within normal ranges, and physical examination findings were unremarkable with no abdominal tenderness, mass, bruit, or varicocele. Laboratory test results showed a hemoglobin level of 11 g/dL; white blood cell count of 12,550/mm3, and platelet count of 188,000/mm3. Urine analysis revealed 2+ blood, 50-100 red blood cells (RBCs) per high-power field (HPF) and no proteinuria. To determine the cause of the flank pain, abdominal ultrasonography was performed, which revealed an infrarenal AAA measuring 4.5 cm in diameter, without renal stones or hydronephrosis. Computed tomography angiography (CTA) of the abdomen showed compression of the retro aortic left renal vein at the 3rd lumbar vertebral body, between the aneurysmal sac and the vertebral body, without renal vein duplication or circum-aortic renal vein. The left renal vein exhibited a pre-compressed diameter of 9.24 mm (at left renal hilum) and a compressed diameter of 3.25 mm, resulting in a compression ratio of 2.84, suggestive of NCS (Fig. 1). Given the evident compression of the left renal vein due to the aneurysmal sac, further assessments such as intravascular ultrasound (IVUS) or pressure gradient measurement were not performed. Alternative procedures to open surgery such as renal vein stenting or endovascular aneurysm repair (EVAR) would not have been feasible due to the compressive effect of the AAA.

Figure 1. Sagittal images of computed tomography scan showed pre-compressed left renal vein (A) and compressed renal vein due to aneurysm sac (B).

Based on the CTA results, we performed a median laparotomy for open repair of the AAA using a Dacron graft for decompression of the AAA to the left renal vein. The proximal anastomosis was performed below the renal artery, while the distal anastomosis was performed at the aortic bifurcation. Intraoperative findings showed an aneurysmal sac 4.5 cm that compressed the left renal vein and caused distal dilation of the vein. The postoperative course was uneventful, and a follow-up CTA performed at one month after the surgery demonstrated an improved compression ratio (from 2.84 to 1.13; pre-compressed diameter 9.0 mm, post compressed diameter 7.9 mm; Fig. 2). The patient’s abdominal symptoms improved, and postoperative urine analysis revealed a decrease in RBC counts from 50-100 per HPF to 1-2 per HPF.

Figure 2. Preoperative axial images of computed tomography (CT) scan revealed compression of the left renal vein due aneurysm sac (A), and postoperative axial image of CT scan showed improved renal vein compression (B). Preoperative and postoperative axial images of left renal vein at the renal hilum are shown in (C) and (D) respectively. The left renal vein was compressed by the abdominal aortic aneurysm during preoperative period and showed improved after open surgical repair.

DISCUSSION

Anterior-type NCS or renal vein compression syndrome is defined as compression of the left renal vein between the aorta and superior mesenteric artery [2]. Diagnosis can be confirmed through various imaging modalities, including duplex ultrasonography, CTA, magnetic resonance angiography (MRA), or IVUS. For computed tomography and MRA, a diagnosis can be suspected when the angle between the superior mesenteric artery and abdominal aorta is less than 25°-41°, pre-compressed to compressed left renal vein diameter ratio is greater than 2.25-4.9 [2,3,6,7]. If the diagnosis of NCS remains unclear, it can be confirmed with additional test when renocaval pressure gradients exceeds 3 mmHg or IVUS findings indicate compression [2,6,7]. Another rare type of NCS involves the compression of the left renal vein between the aorta and the vertebral body [4,5]. In the case of posterior-type NCS, there is no definitive cutoff ration for left renal vein compression to establish a diagnosis. In this case report, the compression ratio was 2.84 without any other causes of flank pain or hematuria; therefore, we suspected that the clinical condition might have been caused by NCS.

The management of NCS remains controversial, with conservative management being the preferred approach in most cases. Surgical management, such as renal vein transposition, or endovascular stenting of renal vein may be considered for patients with gross hematuria, flank or abdominal pain, anemia, autonomic dysfunction, renal function impairment, or ineffective conservative management [2]. However, the management of posterior-type NCS presents more challenges due to the retro aortic position of the renal vein and its associated direct pressuring effect of the aorta to the vertebral body, which will limit the use of renal vein stents.

In this particular case, NCS was caused by aneurysmal sac compression; therefore, reconstruction of the AAA either by EVAR or open repair could be considered to alleviate the compression. While EVAR technique may lead to aneurysmal sac shrinkage, some patients still exhibit a stable size or delayed reduction in the aneurysmal sac diameter [8]. Open surgical repair can rapidly decompress the renal vein, especially in patients with posterior-type NCS. In this case, we chose open surgical repair of an AAA. The left renal vein was compressed by the AAA, which improved after open surgical repair. In addition, the patient’s hematuria and abdominal pain improved after surgery.

In conclusion, posterior-type NCS is a rare condition. The diagnosis of this type of NCS requires confirmation through imaging studies. Surgical intervention may be considered in selected symptomatic patients after a thorough discussion of the risks and benefits of the intervention. For posterior-type NCS associated with AAA, open surgical repair may represent the optimal choice for decompression of renal vein.

FUNDING

None.

CONFLICTS OF INTEREST

The authors have nothing to disclose.

AUTHOR CONTRIBUTIONS

Concept and design: SO. Analysis and interpretation: CC. Data collection: CC. Writing the article: CC. Critical revision of the article: SO. Final approval of the article: all authors. Statistical analysis: None. Obtained funding: None. Overall responsibility: SO.

Fig 1.

Figure 1.Sagittal images of computed tomography scan showed pre-compressed left renal vein (A) and compressed renal vein due to aneurysm sac (B).
Vascular Specialist International 2023; 39: https://doi.org/10.5758/vsi.230036

Fig 2.

Figure 2.Preoperative axial images of computed tomography (CT) scan revealed compression of the left renal vein due aneurysm sac (A), and postoperative axial image of CT scan showed improved renal vein compression (B). Preoperative and postoperative axial images of left renal vein at the renal hilum are shown in (C) and (D) respectively. The left renal vein was compressed by the abdominal aortic aneurysm during preoperative period and showed improved after open surgical repair.
Vascular Specialist International 2023; 39: https://doi.org/10.5758/vsi.230036

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