(142) Detecting postpartum anal sphincter injuries with three-dimensional endoanal ultrasound: a prospective diagnostic study

Occult obstetric anal sphincter injury (OASIS) is the subject of much debate. Three-dimensional endoanal ultrasound (3D-EAUS), regarded gold standard for anal sphincter evaluation in non-obstetric settings, is suggested to be a better tool for evaluation of OASIS than routine clinical examination. The aim of this study was to compare routine postpartum clinical examination with 3D-EAUS for detecting OASIS.

Study Design:

This prospective diagnostic study included all primipara women with singleton vaginal delivery at Östersund hospital (Sweden) between 1^st Jan 2016 and 31^st Jan 2018.

The routine postpartum clinical examination with inspection and vaginal and rectal palpation as well as 3D-EAUS recordings were performed directly after delivery. Maternal data were obtained from the medical records. The 3D-EAUS recordings were evaluated by an experienced colorectal surgeon specialized in proctology and 3D-EAUS and compared with the clinical findings.

Results:

Of the 554 women with satisfactory 3D-EAUS recordings, 23 (4.2 %) had OASIS according to the clinical examination compared to 71 (12.8 %) with the 3D-EAUS. Among the 23 women clinically judged to have OASIS, only 7 could be confirmed with 3-D EAUS. No significant risk factors were found in the group with clinically detected OASIS. Episiotomy was the only risk factor for OASIS seen with 3D-EAUS.

Conclusion:

OASIS was more frequently detected with 3D-EAUS than with clinical evaluation. Furthermore, only one in three of the clinically observed OASIS cases was confirmed with 3D-EAUS. This indicates that 3D-EAUS is difficult to interpret in an acute obstetric situation and needs further improvement if it is to be a useful tool in detecting OASIS.