{'fraction_non_alphanumeric': 0.02451464297466272, 'fraction_numerical': 0.00970714050674564, 'mean_word_length': 5.14040404040404, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Endovascular treatment of a patient with nutcracker syndrome and pelvic varices involving anterior and posterior renal veins

We have reported a case of a 36-year-old woman with flank and pelvic pain and hematuria. She had posterior nutcracker syndrome and pelvic varices involving one anterior and three posterior renal veins (including one major vein). We used a complete endovascular approach, which included stent implantation in the major posterior renal vein and left gonadal vein embolization. During a 12-month follow-up period, the patient had had no symptoms and good computed tomography results. Endovascular treatment represents a safe and successful option for patients with nutcracker syndrome and pelvic varices involving the anterior and posterior renal veins.

Nutcracker phenomenon is often anterior and, when asymptomatic, is characterized by abnormal outflow from the left renal vein (LRV) into the inferior vena cava due to extrinsic LRV compression, often accompanied by demonstrable lateral (hilar) dilatation and medial (mesoaortic) stenosis. 1 Nutcracker syndrome (NS), in turn, is a well-characterized set of symptoms whose severity is related to the severity of the anatomic and hemodynamic findings. The most reported symptoms are flank and/or pelvic pain and hematuria. Pelvic congestion and varicocele can also occur in women and men, respectively, resulting from reflux in the gonadal vein, which, in this condition, will become the main collateral pathway for LRV drainage. Although NS is a well-defined condition, no consensus has been reached regarding the indications and treatment options. When symptoms are severe, surgical intervention could be necessary. In this setting, endovascular treatment has been widely accepted, with placement of a self-expanding stent, which can be combined with left gonadal vein embolization. This technique is not without complications, with reports of stent migration even into the cardiac chambers and pulmonary artery. [1][2][3][4][5][6] More rarely, the nutcracker phenomenon will be posterior, resulting from LRV compression between the aorta and the spine or even in a circumaortic renal vein. Given that this condition is rare, defining the role of endovascular treatment has been difficult, because no evidence is available of the outcomes for these patients in the long term. [7][8][9][10] In the present report, we have described an endovascular approach to NS and pelvic varices involving the anterior and posterior renal veins in a female patient. She provided written informed consent for the report of her case details and imaging findings. The patient had no complaints and received dual antiplatelet therapy (acetylsalicylic acid 100 mg and clopidogrel 75 mg) for 1 month, followed by monotherapy with acetylsalicylic acid (100 mg) for 6 months.

CASE REPORT
The patient was followed up for 12 months and had no additional complications. The follow-up CT angiography and Doppler ultrasound showed stent patency (Fig 4), complete obliteration of the gonadal vein, and the absence of dilated pelvic veins.

DISCUSSION
Typically, renal vein NS refers to LRV compression between the abdominal aorta and superior mesenteric artery. Some investigators have termed such compression "anterior (or type A) NS" and have used "posterior (or type B) NS" to designate LRV compression between the aorta and spine. [11][12][13] NS refers to the compression of the renal vein appearing like a lever-style nutcracker crushing a nut, and, in the absence of more specific nomenclature for compression between the aorta and spine, we have also used the terms anterior and posterior NS.
In a previous study reported in 2020, we reported a case of anterior NS in a 42-year-old woman with an anterior and a posterior NS successfully treated with endovascular stent implantation in the renal vein anterior to the aorta and left gonadal vein embolization. 14 She showed complete clinical improvement and remained asymptomatic at 12 months postoperatively. In the same report, we identified previous occurrences and discussed the diagnosis and treatment based on a careful literature search of the main databases regarding NS.
At that time and in a new search performed for the present report, we found only two cases of endovascular treatment of NS in patients with a circumaortic renal vein in the literature. Cohen et al 15  Because the symptoms remained unchanged 3 months later, embolization was performed with coils (one 7-mm coil and one 9-mm coil) and injection of 1% sodium tetradecyl sulfate. The patient reported significant improvement in symptoms 7 months after the procedure. 16 In both our previous case and our present report, we used a new self-expanding stent designed for the venous system (Venovo). 14 Because an important concern is stent fracture resulting from the extrinsic force caused by compression between the aorta and spine, we chose the Venovo stent because its physical characteristics of good radial force and stent deployment precision minimize the risk of fracture.
As reported in the three previous cases, we also chose stent implantation in the renal vein portion anterior to the aorta for our present case, because external compression between the superior mesenteric artery and the aorta (the classic anterior NS) is certainly less significant than that between the aorta and spine. 10 Femoral access proved to be a more favorable option owing to the angulation, which provided greater support for the guide wire to navigate the stent with correct positioning for its release. Based on our previous experience, we chose 3% polidocanol as the sclerosing agent because it is widely used in Brazil for sclerotherapy. Based on this new rare case of a patient with an anterior and a posterior renal vein and NS, we strongly suggest that endovascular treatment with gonadal vein embolization and stent implantation in the anterior or posterior renal vein a priori has no significant differences compared with the endovascular approach for regular anterior NS from a technical viewpoint.