Left renal vein variants are not commonly observed in the general population. Usually, the renal vein runs in front of the aorta before entering the inferior vena cava, while the most common variants include the presence of a circumaortic or retroaortic renal vein. However, when present, left venal rein variants are important to recognize due to their potential clinical and surgical relevance. In this regard, CE-CT is an instrument with high sensitivity and specificity in detecting vascular anomalies and can certainly help diagnose. In this article, we present a unique case of a left venal rein compressed between the left iliac artery and vertebral bodies associated with the presence of a superior mesenteric artery Syndrome, another rare entity that occurs when the duodenum is compressed between the aorta and the superior mesenteric artery.

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Nutcracker syndrome (NCS) is a rare cause of pelvic venous congestion syndrome and is secondary to either compression of the left renal vein in its normal anatomic position by the superior mesenteric artery and aorta or less commonly when the left renal vein is in a retroaortic position, compressed between the aorta and the spine. We herein present a unique case of NCS in a female patient with a history of chronic pelvic pain and venous congestion. We also review the literature and discuss the diagnostic modalities, differential diagnosis, and various open surgical and endovascular options for NCS.

Thrombosis of the left renal vein (LRV) is a rare occurrence usually associated with hypercoagulable disorders. It may also be caused by extrinsic compression due to anatomical variations. Such variations, known as nutcracker phenomenon (NP), are usually completely asymptomatic, and they have been described in three variants: a narrowed aortomesenteric angle (AMA) with entrapment of the LRV; a second, rarer variant with an anomalous retro aortic LRV compressed between the abdominal aorta (AA) and the spine (posterior nutcracker syndrome, PNCS); and a third variant with a duplicated LRV with a pre- and retroaortic course, compressed both anteriorly and posteriorly. The development of symptoms secondary to NP is mainly due to renal congestion, often difficult to identify, and includes flank pain, ipsilateral varicocele, hematuria, and orthostatic proteinuria, among others. The most severe complication of NCS is LRV thrombosis with or without associated predisposing prothrombotic factors. The present case associates a PNCS to LRV thrombosis with a floating thrombus in the inferior vena cava and pulmonary embolism.

We report a unique case of unusual drainage of the bifurcated retroaortic left renal vein, with the cranial wider branch draining into a dilated lumbar azygos vein and caudal thinner branch connecting with the inferior vena cava. The right renal vein was duplicated. The anomaly was discovered on multimodal 18F-labeled fluorodeoxyglucose positron emission tomography/computed tomography performed for oncological purposes. The basis enabling occurrence of such variation was probably persistent developmental extra left-right venous connections, intercardinal, or intersupracardinal, depending on the theory. The embryology of the chest and abdominal veins is a complicated process and there is no unanimity concerning its concepts. The old models are currently being questioned and reevaluated. Knowledge of possible variants of renal and azygos veins course is important from clinical, imaging, and surgical points of view. The retroaortic left renal veins course may sometimes cause pain, hematuria, proteinuria, and pelvic congestion syndromes. Dilated parts of uncommonly located veins, because of assuming a nodular shape on transverse images, may be mistaken for abnormal lymph nodes, other tumors or aneurysms on imaging. During a variety of surgical procedures, including venous sampling, renal transplantation, or any retroperitoneal surgery, knowledge of an aberrant venous course may be important for the success of the procedure and may be crucial even earlier during the qualification process.

A 58-year-old man presented with severe hematuria of unknown origin and intermittent left flank pain for 8 months, and he was diagnosed with posterior nutcracker syndrome. He underwent prosthetic left renocaval bypass with complete resolution of symptoms. Computed tomography showed a functional graft between the left renal vein and caval vein. This technique is a feasible choice for surgical treatment of posterior nutcracker syndrome with satisfactory results.

An 8-year-old girl was enrolled in hospital with intermittent gross hematuria in a period of 3 years. Bloody efflux from the left ureteral orifice was diagnosed in this patient with urethrocystoscopy. A retroaortic left renal vein appeared to be compressed by the aorta as detected by computerized tomography. The left renal vein was compressed between the aorta and the spine. A groove in the anterior surface of the left renal vein was detected. A transposition surgery of the left renal vein to a site in front of the aorta was performed for the patient. The patient was discharged after recovery and the hematuria symptom was not found during the 15-month follow-up investigation.

BACKGROUND: Posterior Nutcracker syndrome (NCS) is a rare anomaly in which the left renal vein passes behind the aorta which compresses it against the vertebral column, restricting the venous drainage of the left kidney.
METHODS: A 46 year-old lady presented with intermittent painless hematuria for 6 years. Urinalysis showed microscopic hematuria. An abdominal CT scan showed left renal vein duplication with the retroaortic branch trapped between the vertebral column and the aorta at the level of the aortic bifurcation, suggestive of posterior NCS. There were multiple small cortical cysts, sand-like stones in the left kidney and duplication of both right and left renal arteries.
CONCLUSIONS: Posterior NCS in a patient with a duplicated left renal vein may not show all the clinical features of a typical NCS as the elevated pressure due to compression is dissipated through the pre-aortic branch of the duplicated renal vein. CT Angiography can be helpful in such a patient with multiple abnormalities. Management can range from simple surveillance to nephrectomy depending on the symptoms and renocaval pressure gradient.
CONCLUSIONS: Although posterior NCS is a rare anomaly of the left renal vein, it should be considered in the differential diagnosis of haematuria.