Abnormalities of Fetal Situs

Abstract

The incidence of congenital heart disease is most commonly reported in 8 per 1000 live births. Situs anomalies are among the least common forms of congenital heart disease. This study defines situs and describes the variations of fetal situs anomalies. Situs refers to the arrangement of the viscera, atria, and vessels within the body. Situs solitus describes the normal arrangement; situs inversus describes inverted arrangement of the viscera and atria; and situs ambiguous (also referred to as heterotaxy) describes disturbances in arrangements that can neither be identified as solitus nor inversus. This review will concentrate on heterotaxy, as it is the most complicated situs abnormality to define, classify, and study. Prognosis of heterotaxy is variable but most correlated with cardiac anatomy. Management is concentrated on numerous cardiac operations and requires a multidisciplinary approach to address coexisting congenital anomalies.

Anatomy, embryology, and imaging of situs ambiguous with polysplenia and left IVC

“…Human embryonic development is characterized as a highly ordered and nonrandom process that leads to an evident left-right asymmetry [5] . During embryogenesis, different processes are activated with the purpose of generating the organs that make up the human anatomy, as well as their correct positioning [6] . Asymmetry during embryonic development is determined by the ciliary dynamics of the primitive node.…”

“…On the other hand, they are also usually associated with a defect of the common AV canal, which generates a hemodynamic imbalance that functionally generates a single ventricle with a high incidence of outflow obstruction to the pulmonary territory [10 , 11] . Extracardiac manifestations include the presence of a symmetrical liver, midline stomach with associated intestinal malrotation, trilobed lungs and bilateral hypoarterial bronchi [12] .…”

Prenatal Diagnosis of Dextrocardia with Complex Congenital Heart Disease Using Fetal Intelligent Navigation Echocardiography (FINE) and a Literature Review

“…This term is most commonly understood to mean a heart lying predominantly in the right hemithorax [46]. Others describe dextrocardia as both cardiac placement on the anatomic right side, and a cardiac apex that points to the anatomic right [47]. Many authors use the definition of primary dextrocardia, a cardiac malposition in which the major axis of the heart (from base to apex along the interventricular septum) points to the right, and is due to an intrinsic developmental abnormality [1–5].…”

Situs Inversus Totalis

“…Internal organ development of the embryo is asymmetric, with the normal left and right sides of the body being different in form (1). The "normal" orientation of the heart and viscera is referred to as situs solitus.…”

“…The "normal" orientation of the heart and viscera is referred to as situs solitus. Changes in normal laterality can range from mirror image situs inversus totalis, to varying degrees of partial changes referred to collectively as situs ambiguous (1,2). The severity of the congenital malformation is often categorized based upon the prevalence of associated anomalies, which can include complex congenital heart defects (3).…”