Tubal ring sign “bagel & blob sign”

Feature	Bagel Sign	Blob Sign
Appearance	Echogenic ring with central hypoechoic area (“tubal ring”)	Ill-defined, heterogeneous adnexal echogenic mass
Specificity	More specific for ectopic	Less specific, suggestive only
Pathology	Gestational sac with trophoblastic tissue	Hematoma/clot or ectopic mass without clear sac
Diagnostic value	Strongly supports ectopic pregnancy; definitive if yolk sac/embryo seen	Raises suspicion but not confirmatory

![The “blob sign.” A 32-year-old pregnant patient (6 weeks gestational age based on last menstrual period) presented with pelvic pain and vaginal bleeding. Beta-hCG measured 225 mIU/mL. Grayscale pelvic ultrasound of the left adnexa demonstrated a nodule or “blob” like structure (arrow) abutting the ovary (arrowhead).

Lima D, Revels JW, Mattinson T, Wang SS. “The bagel and blob signs in tubal ectopic pregnancy.” Radiology Case Reports. 2021;16(7):1851-1853. doi:https://doi.org/10.1016/j.radcr.2021.04.022](attachment:ac945862-d08a-4300-9007-5b4ff4d8df81:1-s2.0-S1930043321002302-gr1.jpg)

The “blob sign.” A 32-year-old pregnant patient (6 weeks gestational age based on last menstrual period) presented with pelvic pain and vaginal bleeding. Beta-hCG measured 225 mIU/mL. Grayscale pelvic ultrasound of the left adnexa demonstrated a nodule or “blob” like structure (arrow) abutting the ovary (arrowhead).

Lima D, Revels JW, Mattinson T, Wang SS. “The bagel and blob signs in tubal ectopic pregnancy.” Radiology Case Reports. 2021;16(7):1851-1853. doi:https://doi.org/10.1016/j.radcr.2021.04.022

![The “bagel sign.” A 32-year-old pregnant patient (6 weeks gestational age based on last menstrual period) re-presented with pelvic pain and vaginal bleeding. Beta-hCG measured 1657 mIU/mL compared to 225 mIU/mL 3 days prior. (a) Grayscale pelvic ultrasound of the left adnexa demonstrates a ring-like structure with a thick, solid, hyperechoic periphery and fluid centrally: the “bagel sign” (arrowhead) (calipers along the periphery were placed to measure the size of the structure). (b) Bagel animation overlaid on top of the sonographic finding. Ectopic pregnancy was confirmed clinically.

Lima D, Revels JW, Mattinson T, Wang SS. “The bagel and blob signs in tubal ectopic pregnancy.” Radiology Case Reports. 2021;16(7):1851-1853. doi:https://doi.org/10.1016/j.radcr.2021.04.022](attachment:bbdbf71c-56d5-47fc-9d5a-00aa4fcc1982:1-s2.0-S1930043321002302-gr2.jpg)

The “bagel sign.” A 32-year-old pregnant patient (6 weeks gestational age based on last menstrual period) re-presented with pelvic pain and vaginal bleeding. Beta-hCG measured 1657 mIU/mL compared to 225 mIU/mL 3 days prior. (a) Grayscale pelvic ultrasound of the left adnexa demonstrates a ring-like structure with a thick, solid, hyperechoic periphery and fluid centrally: the “bagel sign” (arrowhead) (calipers along the periphery were placed to measure the size of the structure). (b) Bagel animation overlaid on top of the sonographic finding. Ectopic pregnancy was confirmed clinically.

Lima D, Revels JW, Mattinson T, Wang SS. “The bagel and blob signs in tubal ectopic pregnancy.” Radiology Case Reports. 2021;16(7):1851-1853. doi:https://doi.org/10.1016/j.radcr.2021.04.022

![A 31 year-old woman had intrauterine contraceptive device, presented with lower abdominal pain and elevated β-hCG. Grey-scale (A), color Doppler (B), and power Doppler (C) transvaginal ultrasound images show left adnexal echogenic ring with central hypoechogenicity (asterisk) and peripheral increase flow resembling ring of fire (arrows). No viable fetal pole is clearly detected. Ultrasound examination of the uterus showed intrauterine contraceptive device in place with no intrauterine pregnancy.

Aljebreen, A.M., Aljohani, I.M., Alshabanat, A.Z. et al. The tubal ring and ring of fire signs. Abdom Radiol 41, 2310–2311 (2016). https://doi.org/10.1007/s00261-016-0905-6](attachment:354fa067-e23d-43f5-aea0-02f71fc18c29:261_2016_905_Fig2_HTML.webp)

A 31 year-old woman had intrauterine contraceptive device, presented with lower abdominal pain and elevated β-hCG. Grey-scale (A), color Doppler (B), and power Doppler (C) transvaginal ultrasound images show left adnexal echogenic ring with central hypoechogenicity (asterisk) and peripheral increase flow resembling ring of fire (arrows). No viable fetal pole is clearly detected. Ultrasound examination of the uterus showed intrauterine contraceptive device in place with no intrauterine pregnancy.

Aljebreen, A.M., Aljohani, I.M., Alshabanat, A.Z. et al. The tubal ring and ring of fire signs. Abdom Radiol 41, 2310–2311 (2016). https://doi.org/10.1007/s00261-016-0905-6

Clinical Pearls:

Tubal Ring = Bagel Sign: These terms are often used interchangeably; "bagel" emphasizes the similarity in appearance to the food item.
Blob Sign: More ambiguous, often requires clinical correlation with β-hCG and follow-up. It is not diagnostic on its own.
A "live ectopic" (extrauterine gestation with fetal cardiac activity) is the most definitive sonographic sign of ectopic pregnancy.

Imaging Correlation:

In cases with β-hCG >1500 IU/L and no intrauterine pregnancy seen on transvaginal ultrasound, identification of a tubal ring or blob sign in the adnexa significantly increases suspicion for ectopic pregnancy.
Color Doppler helps differentiate vascular tubal ring (ectopic) from avascular corpus luteum cysts.

Further reading:

https://doi.org/10.1007/s00261-016-0905-6

https://doi.org/10.1016/j.radcr.2021.04.022