Antenatal ultrasound diagnosis of small bowel non-rotation in complex left isomerism: a case report

PRESENTATION OF CASE: A multiparous expectant mother was referred to our tertiary unit at 23 weeks with a complex fetal cardiac anomaly in the context of suspected heterotaxy syndrome. The cardiac findings were consistent with isomerism: the fetal cardiac position was levocardia with a single functioning double outlet ventricle and AV valve, pulmonary stenosis, and interrupted inferior vena cava (IVC) with azygous continuation. The fetal abdominal situs was also altered, with the stomach to the right, and the hepatobiliary system midline to left. The spleen was not identified antenatally or postnatally. At 36 weeks, ultrasound revealed an abnormal bowel pattern with small bowel loops on the right side of the abdomen and large bowel on the left, suggesting a diagnosis of non- rotation. The infant was delivered vaginally at 39 weeks. The cardiac diagnosis and non-rotation of the small bowel were confirmed by postnatal echocardiography and contrast fluoroscopy. DISCUSSION: Heterotaxy syndrome is traditionally classified into right or left isomerism depending on how and where the organs are anatomically arranged. The case presented here demonstrates mixed laterality and prenatal ultrasound features of non-rotation. CONCLUSION: It is important to be informed of the embryological variants of isomerism and actively seek antenatal evidence of bowel non-rotation in such cases.