Situs Revisited: Imaging of the Heterotaxy Syndrome

Abstract

Situs anomalies present a diagnostic challenge to radiologists because of the overlapping spectrum of findings commonly seen in asplenia and polysplenia. In a series of 21 patients with a diagnosis of heterotaxy syndrome, all 11 asplenic patients and seven of 10 polysplenic patients had congenital heart disease. Although there was a variety of complex congenital heart disease, the most common type in both patient groups was a common atrioventricular canal. In both groups, the laterality of the aorta and stomach was quite variable, but intestinal malrotation was a constant feature. In 11 asplenic patients, the most frequent findings were a bridging liver (10 cases), absent spleen (10 cases), and left-sided inferior vena cava (nine cases). Only seven of these patients had an aorta ipsilateral to the inferior vena cava, contrary to previous thought that this finding was specific for asplenia. In the 10 polysplenic patients, bridging livers were less frequent (five cases), single (six cases) or multiple (four cases) spleens were seen, and azygous continuation with interruption of the inferior vena cava was usually present (eight cases). Although not pathognomonic of polysplenia, inferior vena cava interruption with azygous or hemiazygous continuation is the most common anatomic finding of this condition. Although the terms asplenia and polysplenia are helpful in suggesting the typical anatomy, both syndromes encompass an overlapping spectrum that needs to be described individually and may best be called heterotaxy syndrome.

Heterotaxy syndrome: a case report

“…The loss of such orderly arrangement may characterize situs inversus or a disordered and variable arrangement (heterotaxy syndrome). Heterotaxy syndrome presents an approximate incidence of 1:10,000 births and is slightly more prevalent in men, at a ratio of 2:1 (3,5) .…”

“…Cardiac alterations are less frequently found and milder, a fact that explains a higher prevalence of such findings in individuals of more advanced ages (3) .…”

Concurrent dextrogastria, reverse midgut rotation and intestinal atresia in a neonate

“…[4] There have been reports on the overlapping spectrum of situs anomalies isolating organs or encompassing both the thoracic and abdominal viscera. [5] From our literature, the occurrence of dextrogastria, multiple jejunal atresia and inverse rotation of the intestine with levocardia in a neonate have not been reported in Africa, although there are reports of isolated intestinal malrotation in children of Nigeria.…”

“…[1][2][3] Situs inversus occurs in approximately 1 in 8,500 people; however, the incidence of situs inversus abdominus (SIA) varies between 1 in 4,000 and 1 in 20,000 live births and may present a diagnostic and management challenge to the clinician and radiologist. [4] Situs ambiguous or heterotaxy implies a disordered organ arrangement in the chest or abdomen, whereas complete situs inversus implies that the organs of the chest and abdomen are arranged in opposite positions (the heart is on the right (dextrocardia) as is the twolobed lung, while the liver, spleen and three-lobed lung are on the left). We report a case of neonatal intestinal obstruction from multiple intestinal atresias and the inverse rotation of midgut in a patient with dextrogastria and a review of recent literature.…”

Congenital Thoracic Venous Anomalies in Adults: Morphologic MR Imaging

“…13 The hemiazygos continuation of the IVC is a less frequently seen abnormality, with 3 possible paths of drainage being described: (1) through the azygos vein; (2) into a persistent LSVC; and (3) into a normal right SVC (coursing through the accessory hemiazygos vein and LBCV). 14 Although previously thought to be associated with severe congenital heart disease and heterotaxy syndrome, 15 both these anomalies are being increasingly documented in asymptomatic patients since the advent of cross-sectional imaging. Awareness of these anomalies avoids misdiagnosing enlarged azygos or hemiazygos veins for retrocrural adenopathy.…”