Circumaortic Left Renal Vein Associated with Juxtarenal Abdominal Aortic Aneurysm

Abstract

The patient was an 82-year-old man who was found to have a juxtarenal abdominal aortic aneurysm accompanied by a circumaortic left renal vein (CLRV). During dissection of the proximal anastomosis site the CLRV was injured, but was successfully repaired. A graft implantation was performed below the renal arteries. The incidence of CLRV is thought to be rare, however it is found in 7% of cadavers donated for anatomy. CLRV may cause unexpected bleeding by inadvertent dissection of the abdominal aorta. To prevent unexpected bleeding, surgeons should always keep in mind this potential risk when performing surgery.

Introduction

Knowledge of the location and anatomy of the renal vascular pedicle is useful for vascular and general surgeons, urologists, and interventional radiologists.^1–6) In particular, anatomical variations and congenital anomalies of the left renal vein are important for vascular surgeons. Preoperative knowledge of such anomalies can help with operative planning and can reduce the risk of major bleeding in abdominal aortic surgery.

Here, we present a case of juxtarenal abdominal aortic aneurysm (AAA) with circumaortic left renal vein (CLRV) anomaly.

Case Report

An 82-year-old man was referred by his general practitioner to our hospital for elective repair of a large juxtarenal AAA. He had a medical history of hypertension, hyperlipidemia, and cerebral infarction. Physical examination revealed an abdominal pulsatile mass around his navel.

A contrast-enhanced computed tomography (CT) scan confirmed the presence of a juxtarenal AAA, which measured 81 mm at its maximum diameter and involved the bifurcation and both of the proximal common iliac arteries. The left renal vein ran through the retroaortic space. These findings led to the pre-operative diagnosis of a juxtarenal AAA accompanied by a retroaortic left renal vein (Fig. 1).

Fig. 1.

Preoperative contrast-enhanced computed tomography (CT) scan. (A, B) Juxtarenal abdominal aortic aneurysm (AAA) with a maximum diameter of 81 mm is seen above the bilateral renal arteries. (C) The left renal vein (LRV) traversing behind the aorta is seen. The LRV traversing in front of the aorta is not seen.

Surgery was performed through a standard transperitoneal route. The juxtarenal abdominal aorta was dissected first and taping of the bilateral renal arteries was performed. In addition to the normal left renal vein at the front of the abdominal aorta, there was another left renal vein running behind the abdominal aorta near the renal artery. Therefore, intraoperative diagnosis of CLRV was made. After systemic administration of heparin, the suprarenal abdominal aorta, the bilateral renal arteries, and the bilateral common iliac arteries were clamped. During dissection of the abdominal aorta at the proximal anastomosis site, the left renal vein running behind the aorta was injured. After controlling bleeding by pressing the circumference, suture repair was carried out without ligation and successfully repaired. Graft implantation was performed using a 24 × 12 mm Y-shaped vascular prosthesis (J Graft SHIELD NEO, JUNKEN MEDICAL CO., Ltd., Tokyo, Japan) just below the renal arteries. Operative time was 335 minutes, and total blood loss was 1300 ml. The warm ischemic time of the bilateral renal arteries was 32 minutes.

The patient’s postoperative course was uneventful and he was discharged on the 9th postoperative day in good condition. At his 36-month follow-up, the patient was doing well, with serum creatinine of 0.85 mg/dL. Multislice CT showed that the pressure on the retroaortic part of the left renal vein was alleviated, the left renal vein in front of the aorta also became apparent and the presence of CLRV became obvious (Fig. 2).

Fig. 2.

Postoperative contrast-enhanced computed tomography (CT) scan. (A) Anterior component of the circumaortic left renal vein (CLRV) was revealed after compression by the aneurysm was released. (B) Anterior and posterior components of CLRV merge into one, and Type I CLRV was diagnosed.

Discussion

During the 7th to 8th week of embryonic development, the subcardinal veins develop and the anastomosis between the subcardinal veins forms the left renal vein. Unusual persistence or regression of the amastomoses at this level results in the formation of left renal vein anatomical variations, such as CLRV and retroaortic left renal vein (RLRV).⁶⁾ Natsis, et al. classified CLRV into 3 morphological types shown in Fig. 3. In Type I morphology, one left renal vein (LRV) splits into 2 branches, a preaortic and a retroaortic, draining into the inferior vena cava (IVC). In Type II, 2 separate LRVs are formed, one preaortic and the other retroaortic, draining into the IVC. In Type III, either there are anastomoses between the preaortic and retroaortic vein that may be multiple or not, or there may be multiple preaortic or retroaortic renal veins without anastomoses.⁷⁾ The case presented here was a Type I CLRV. Understanding these variations of the left renal vein based on the embryology is important in the prevention of venous injury during abdominal aortic surgery.

Fig. 3.

Classification of the circumaortic left renal vein (CLRV) by morphology.⁷⁾ Type I, One left renal vein (LRV) splits into two branches, a preaortic and a retroaortic, draining into the inferior vena cava (IVC). Type II, Two LRVs, one preaortic and the other retroaortic, draining into the IVC. Type III, Either there are anastomoses between the preaortic and retroaortic vein that may be multiple or not, or there may be multiple preaortic or retroaortic renal veins without anastomosis.

We have treated 580 abdominal vascular cases in the past 10 years. Among these, the incidence of CLRV was as low as 0.2%. However, in a review and meta-analysis on variations of the left renal vein, Shuang-Qin, et al. reported that the median incidence of CLRV was 7.0% in cadavers examined, and 1.8% in clinical cases examined, and pointed out that there is no association between actual anatomy and clinical manifestations.⁸⁾ This discrepancy suggested that the detection of CLRV by CT or MRI is relatively difficult compared with that in cadaver dissection. Therefore, CLRV is not a rare anatomical occurrence, and thus, it is necessary to always pay attention to the possible presence of CLRV in preoperative diagnostic imaging.

With the recent advances in imaging techniques, the diagnosis of developmental anomalies of the left renal vein has become possible prior to surgery. However, the detection rate is not adequate at about 0.9%–6.3%, even by multislice CT scan or MRI angiography.^9,10) Surprisingly, there are also reports stating that angiography was superior to CT and MRI in the detection of CLRV.⁸⁾ Therefore, the difficulty of preoperative diagnosis is still present. Also, in cases of emergency surgery, such as for rupture of a vessel, the patient is often transported to the operating room with only a plain CT scan done and adequate diagnostic imaging may not be possible. As a precaution, it is important to always check the morphology of the left renal vein when dissecting the infrarenal abdominal aorta during surgery.

During abdominal aortic surgery, when there are developmental anomalies of the renal vein, one of the biggest problems is unexpected venous injury. In one surgical series published by Brener, et al., 22 left renal vein anomalies were identified. Venous injury occurred in half of the cases of left renal vein anomalies encountered. In 2 cases, injuries necessitated nephrectomy to control the hemorrhage, and 2 patients died as a result of hemorrhage.¹⁾ Shindo, et al. also reported a case of CLRV in which bleeding was similarly difficult to manage. It was stated that the risk of venous injury is higher in patients with a CLRV than in those with an IVC anomaly and this is because the large anterior component of a CLRV can easily mislead the surgeon during operation into thinking that the development of left renal vein is normal and that there is no retroaortic component.²⁾ Particularly in Type II CLRV, since the posterior component is independent, it is easily mistaken for a normal left renal vein. When we proceeded to perform dissection of the proximal anastomosis site, it inadvertently resulted in venous injury. Fortunately, we were able to repair it easily. However, it is difficult to control this bleeding in some cases and it is necessary to dissect and repair it after clamping the aorta to ensure an unobstructed field of view. Also, the retroaortic component of CLRV is fragile and does not take a definite route; therefore, it requires special attention to dissect the proximal anastomosis site of the aorta. Once the anomaly is recognized, proximal control can usually be secured at a higher position, and in general it is not necessary to encircle the aorta with a tape. Also, it is recommended to dissect only the anterior and lateral aorta and clamp the aorta with the surrounding tissue using a straight clamp.^1–3) Of further note, intraluminal anastomosis of the graft without dissecting the posterior wall is one way to prevent bleeding.

Conclusion

We reported a case of CLRV associated with Juxtarenal AAA. Preoperative imaging diagnosis is one of the most important factors in avoiding inadvertent venous injury and bleeding during surgery. However, care must be taken in abdominal aortic surgery, particularly in emergency surgery when sufficient preoperative examination cannot be performed, it is necessary to always keep in mind this possibility and to be familiar with the anatomical features when performing surgery.

Disclosure Statement

The authors have no conflicts of interest to declare.