Case report

Following images show an important and transient sign seen in the early midtrimester, useful to diagnose a common anomaly.

The sign is a transient and distended right-sided sigma useful in the diagnosis of low anal atresia. This finding usually dissapear at 20-22 weeks of pregnancy, and even the ¨target sign¨ (normal annus) could be present.
This case was confirmed after birth.

Images 1, 2; video 1, 2: 2D axial and sagittal images at 15 weeks of pregnancy showing the distended color (arrows) on the right side of the fetus, posterior to the urinary bladder.

Videos 3, 4: the sign spontaneously dissapeard at 22 weeks and even the target sign is visible.