Inferior vena cava anomalies and variations: imaging and rare clinical findings
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The aim of this paper is to summarize imaging findings of some frequent and infrequent inferior vena cava (IVC) anomalies and variations.
IVC anomalies should be suspected in patients presenting with pulmonary emboli, chronic pain, and deep vein thrombosis. To correctly characterize and classify IVC anomalies and variations is of crucial importance for proper planning of surgical interventions and thus for avoiding serious complications.
• IVC anomalies should be suspected in patients with pulmonary emboli, pain, and venous thrombosis.
• Awareness of IVC anomalies and variations is crucial for clinical and surgical procedures.
• Unawareness of these anomalies may lead to severe and deadly complications.
KeywordsInferior vena cava anomalies Multidetector row computed tomography Magnetic resonance imaging IVC Inferior vena cava variations
Anomalies of the inferior vena cava (IVC) and its variations were first described by Abernethy in 1793 in a 10-month-old child with polysplenia and dextrocardia who presented with a congenital mesocaval shunt and continuation of IVC with the azygos vein (CCA) [1, 2, 3]. The IVC develops sequentially, primarily between the sixth and eighth gestational weeks, with the formation of anastomoses and posterior regression of three paired veins: subcardinal, supracardinal, and postcardinal [2, 3, 4, 5, 6]. Because of this complexity in its embryogenesis, there are numerous anatomical forms and variations of IVC [2, 3, 5, 6, 7, 8].
Anomalies of IVC are usually visualized by noninvasive imaging techniques including multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI) [2, 9]. In fact, these anomalies can be misdiagnosed as a mass lesion if variations and anomalies such as the double IVC, agenesis of infrarenal IVC, left IVC, and enlarged azygos vein are overlooked. Moreover, awareness of these variations is crucially important for cardiopulmonary surgeries. For instance, in cases with left IVC, the infrarenal placement of an IVC filter may be difficult to perform through the atransjugular approach [2, 3, 4, 10].
In this article, we present the imaging findings and rare clinical variations of IVC anomalies with associated variations and diseases.
All CT studies were performed on a 64-channel MDCT scanner (Aquilion; Toshiba, Japan). Routine abdominal tomography scans and the portal phase images used to interpret the venous structures in the abdomen were obtained 60–70 s after the administration of 70–80 ml non-ionic iodinated contrast material and 40 ml saline at injection rates of 2.5-3 ml/s. The CT scans were evaluated on a workstation (Vitrea; Toshiba, Japan) using postprocessing techniques including maximum intensity projection, multiplanar reconstruction, and volume rendering. Routine MRI scans were obtained on a 1.5 T MR system (HDxT; General Electric, USA) following the injection of 15 ml gadolinium-based contrast material followed by 25–30 ml saline solution at a speed of 1.8 ml/s. The MR images were evaluated on a dedicated workstation (AW volume share 4; General Electric, USA) using the abovementioned postprocessing techniques.
Specific IVC variations and anomalies including associated venous variations such as continuous azygos (CA) and hemiazygos CHA) veins and other collateral pathways (deep, portal, median, and superficial) were recorded using a standardized form.
In the current literature, there is no consensus about the classification of IVC anomalies and variations. In a study about the development of the IVC in the domestic cat performed in 1920, Huntington and McLure proposed a theoretical classification system for IVC anomalies and suggested that there could be 14 theoretical variations. In this paper, the authors stated that 11 of these 14 variants had been observed either in cat or in humans. Nevertheless, they observed other additional anomalies in humans such as abnormal development of the prerenal division of the IVC and persistence of the renal collar . Today, the most frequently encountered and published anomalies include retroaortic left renal vein, left IVC, double IVC, circumaortic left renal vein, interruption of IVC with azygos and hemiazygos continuation, absence of the infrarenal IVC, and circumcaval ureter [2, 8, 12]. In general, the prevalence of IVC anomalies is reported as 0.5 % in the world . In the present pictorial essay we summarize imaging findings of ten patients with frequent and infrequent IVC anomalies including absence of infrarenal IVC, left IVC, double IVC, interruption of IVC with CA, left retroaortic vein, and accessory continuous hemiazygos vein. Of these ten patients, five were men and five women with a mean age of 45 (range: 11–65 years).
Absent infrarenal IVC
Absent infrarenal IVC is the rarest and the most striking congenital anomaly of the IVC , and can be either complete or incomplete absence with preservation of the suprarenal segment [2, 3, 4, 14, 15]. Complete absence of IVC occurs when the three paired venous systems (subcardinal, supracardinal and postcardinal systems) fail to develop properly. Complete absence of the infrarenal IVC with preservation of the suprarenal segment is highly infrequent. Absent infrarenal IVC results in the failure of development of the posterior cardinal and supracardinal veins . D’Archambeau and Milner proposed that the absent infrarenal IVC is caused by the intrauterine or perinatal thrombosis of the IVC, based on the theory that a single embryological failure cannot explain the absence of infrarenal IVC. This theory is supported by numerous researchers [2, 15, 16].
Absence of IVC may be accompanied by symptoms of venous insufficiency in the lower limbs or idiopathic deep vein thrombosis (DVT), particularly in early adulthood [4, 16, 17]. Moreover, absence of IVC may also lead to insufficient blood flow, causing blood stasis in lower limbs and formation of varices, which is generally bilateral in more than half of the patients. However, this bilateral tendency contradicts the reported incidence of less than 10 % in the DVT patients presenting with a normal IVC [2, 3, 8, 9, 18, 19]. These conditions lead to the formation of collateral pathways. Eyraud divides the collateral pathways into four systems: deep, portal, median, and superficial .
The deep pathways we mentioned previously were open in all these three patients with left IVC.
Typical double IVC has a prevalence of 0.2 %-3 % [2, 3]. Double IVC is caused by persistence of both the left and right supracardinal veins. The left IVC may cross over and join the right IVC. In some patients, remarkable differences may be present regarding the size of the left and right IVC. This anomaly can also be associated with other variations including right double IVC, double IVC with the retroaortic RRV, and double IVC with CHA of the left IVC [2, 3, 5, 7, 9].
Double IVC with retroaortic RRV and CHA of the IVC can occur in three patterns: (1) hemiazygos vein joins the rudimentary azygos, (2) hemiazygos vein joins the coronary vein of the heart through a persistent left SVC, and (3) accessory hemiazygos vein progresses to the left brachiocephalic vein [2, 3].
Isolated accessory hemiazygos vein
Compliance with ethical standards
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. This research is involving MDCT and MRI imaging of the patients. For this retrospective study, formal consent is not required.
The author(s) received no financial support for the research, authorship, and/or publication of this article.
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