Portal de Periódicos da CAPES

It takes two great vessels to tango: fetal nutcracker phenomenon

2021; Wiley; Volume: 57; Issue: 6 Linguagem: Inglês

10.1002/uog.23602

1469-0705

Ron Charach, S. M. Cohen, Simcha Yagel, D. V. Valsky,

Aortic aneurysm repair treatments

Nutcracker phenomenon (NCP) typically refers to the anatomical compression of the left renal vein (LRV) between the superior mesenteric artery (SMA) and abdominal aorta, resulting in an impeded outflow from the LRV. The impeded outflow is often accompanied by renal venous hypertension with hilar and ureteral dilatation1. Here, we report on a rare case of left-sided inferior vena cava (LIVC) crossing the aorta anteriorly towards the right side and leading to a unique form of fetal NCP. A 32-year-old woman, gravida 4 para 3, was referred to our fetal medicine unit at 25 + 3 weeks of gestation with a suspected abdominal vascular anomaly. Detailed examination using two-dimensional color Doppler imaging revealed an anomalous course of the fetal inferior vena cava (IVC). Using the high-definition flow Doppler ultrasonographic modality, a left-sided infrarenal portion of the IVC was observed, obliquely crossing to the right side, anteriorly to the abdominal aorta and inferiorly to the adjacent SMA, then continuing as a normally positioned, right-sided suprarenal IVC (Figure 1). Along its course, the infrarenal segment of the LIVC drained the LRV. Three- and four-dimensional (3D/4D) color Doppler with HDlive mode (Voluson E10, GE Healthcare, Zipf, Austria) allowed us to observe clearly the spatial relationships between the anomalous IVC, aorta and SMA. Careful evaluation of the vasculature demonstrated that the SMA, due to its acute downward angle, entrapped the LIVC as it crossed over the aorta to the right side, bringing about a rare type of fetal NCP (Figure 2). Among the various anomalies of IVC reported in the literature, the prevalence of LIVC is between 0.2% and 0.5%2. During the 10th week of gestation, when venous system development is completed, the mature singular IVC comprises five confluent segments2–4. In caudal to cranial order, these segments are (1) the iliac veins, derived from the posterior cardinal veins; (2) the infrarenal segment, derived from a persistent portion of the right supracardinal vein; (3) the renal segment, derived from the anastomosis between the right supracardinal and subcardinal veins; (4) the suprarenal segment, derived from a persistent portion of the right subcardinal vein; and (5) the hepatic segment, derived from the vitelline vein (Figure 3). In rare cases, the left supracardinal vein persists instead of the right supracardinal vein, which in turn regresses, leading to the development of LIVC. Normally, the infrarenal LIVC drains into the LRV, which crosses the abdominal aorta anteriorly to join the right renal vein and proceed cranially as a right-sided suprarenal IVC5, 6. In our case, the LRV drained into the infrarenal LIVC on its route, and the LIVC itself crossed the aorta anteriorly towards the right side in a way that resembles two tango dancers during one of their dance moves (Tango sign, Figure 4). This anatomical variant led to this unusual form of fetal NCP. Although, in the present case, we did not detect any signs of renal vein hypertension or dilatation of the collecting system, these morphological changes may manifest later in life due to the changes occurring in systemic vascular pressures following delivery. Many cases of NCP remain asymptomatic. However, NCP may lead to nutcracker syndrome, which is defined by the characteristic clinical symptoms associated with demonstrable morphological features of NCP. Clinical symptoms may present during childhood or adult life and include hematuria, orthostatic proteinuria, flank or abdominal pain, varicocele, pelvic venous congestion syndrome and chronic fatigue syndrome, all of which are secondary to venous hypertension and are often aggravated by physical activity7. The added value of 3D/4D color Doppler and its ability to improve diagnostic accuracy have been investigated over the last decade and proved to be indispensable8. Similarly, in our case, prenatal sonographic visualization of the NCP would not have been possible without applying 3D/4D color Doppler with HDlive mode. Once again, this modality proved useful for examining the spatial relationships within the abdominal vasculature, facilitating our understanding of the idiosyncratic morphology and informing our consultation with the family, regarding possible future complications. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.