Antenatal small-bowel volvulus without malrotation: ultrasound demonstration and discussion of pathogenesis.

We present a case of volvulus without malrotation in a twin fetus where serial antenatal US assisted in the diagnosis and ensured prompt postnatal surgical treatment. When a fetal subumbilical intestinal mass is seen, changing its echogenicity from complex to cystic, and associated with progressive proximal small-bowel obstruction and/or bowel perforation, small-bowel volvulus should be included in the differential diagnosis.