Tubal ring sign

Last revised by Joshua Yap on 10 May 2023

The tubal ring sign, also referred to as a bagel sign or blob sign, is one of the ultrasound signs of a tubal ectopic pregnancy. It comprises an echogenic ring that surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy.

Differential diagnosis

It can be mimicked by a normal corpus luteum. Bimanual examination can be useful to differentiate an ovarian corpus luteum (moves with the ovary) from a tubal ectopic (moves separately from the ovary). Normal ovarian tissue may also be noticeable around a corpus luteum.