The signal void structure at the left lateral wall of the anal canal represents an internal hemorrhoid that shows absent postcontrast enhancement denoting thrombosis.

Hemorrhoids are a common cause of anal pain. They represent vascular submucosal cushions located along three columns in the anal canal at the right anterior, right posterior and left lateral regions. Internal hemorrhoids are located above the dentate line.

Imaging is not recommended for hemorrhoid assessment unless an underlying cause of bleeding is suspected within the colon.