Cogwheel sign

The Cogwheel sign refers to an imaging appearance in pelvic imaging of thickening loops of the Fallopian tube seen on cross section. There are infolding projections (sometimes look like nodules) into the Fallopian tube lumen which is likened to that of a cogwheel. The sign is typically described on ultrasound and is indicative of tubal inflammation in pelvic inflammatory disease with a pyosalpinx or a hydrosalpinx.