Obstetric Anal Sphincter Injuries: Review of Anatomical Factors and Modifiable Second Stage Interventions

Overview

Journal Int Urogynecol J

Publisher Springer

Specialties Gynecology & Obstetrics
Urology

Date 2015 Jun 6

PMID 26044511

Citations 21

Authors

Dharmesh S Kapoor

Ranee Thakar

Abdul H Sultan

Affiliations

Soon will be listed here.

Abstract

Introduction And Hypothesis: Obstetric anal sphincter injuries (OASIs) are the leading cause of anal incontinence in women. Modification of various risk factors and anatomical considerations have been reported to reduce the rate of OASI.

Methods: A PubMed search (1989-2014) of studies and systematic reviews on risk factors for OASI.

Results: Perineal distension (stretching) of 170 % in the transverse direction and 40 % in the vertical direction occurs at crowning, leading to significant differences (15-30°) between episiotomy incision angles and suture angles. Episiotomies incised at 60° achieve suture angles of 43-50°; those incised at 40° result in a suture angle of 22°. Episiotomies with suture angles too acute (<30°) and too lateral (>60°) are associated with an increased risk of OASI. Suture angles of 40-60° are in the safe zone. Clinicians are poor at correctly estimating episiotomy angles on paper and in patients. Sutured episiotomies originating 10 mm away from the midline are associated with a lower rate of OASIs. Compared to spontaneous tears, episiotomies appear to be associated with a reduction in OASI risk by 40-50 %, whereas shorter perineal lengths, perineal oedema and instrumental deliveries are associated with a higher risk. Instrumental deliveries with mediolateral episiotomies are associated with a significantly lower OASI risk. Other preventative measures include warm perineal compresses and controlled delivery of the head.

Conclusions: Relieving pressure on the central posterior perineum by an episiotomy and/or controlled delivery of the head should be important considerations in reducing the risk of OASI. Episiotomies should be performed 60° from the midline. Prospective studies should evaluate elective episiotomies in women with a short perineal length and application of standardised digital perineal support.

Citing Articles

Obstetric Anal Sphincter Injury After Episiometer-Guided Versus Conventional Episiotomy in Instrumental Deliveries: A Randomized Controlled Trial.

Sriram S, Dorairajan G, Rane A Int Urogynecol J. 2024; 35(12):2375-2383.

PMID: 39254842 DOI: 10.1007/s00192-024-05917-x.

Three-Dimensional Transperineal Ultrasound Guiding Early Secondary Repair of Obstetric Anal Sphincter Injury in an Incontinent Patient without Suture Dehiscence.

Orsi M, Cappuccio G, Kurihara H, Rossi G, Perugino G, Ferrazzi E Diagnostics (Basel). 2024; 14(1).

PMID: 38201377 PMC: 10804317. DOI: 10.3390/diagnostics14010068.

Is epidural analgesia an independent risk factor for OASIS? A population-based cohort study.

Eshkoli T, Baumfeld Y, Yohay Z, Binyamin Y, Speigel E, Dym L Arch Gynecol Obstet. 2023; 309(6):2499-2504.

PMID: 37454350 DOI: 10.1007/s00404-023-07150-1.

High Incidence of Obstetric Anal Sphincter Injuries among Immigrant Women of Asian Ethnicity.

Baruch Y, Gold R, Eisenberg H, Amir H, Reicher L, Yogev Y J Clin Med. 2023; 12(3).

PMID: 36769692 PMC: 9917715. DOI: 10.3390/jcm12031044.

Perineal stress as a predictor of performing episiotomy in primiparous women: a prospective observational study.

Xu B, Luo Q, Wu R, Lu Y, Ying H, Xu Y BMC Pregnancy Childbirth. 2022; 22(1):793.

PMID: 36289493 PMC: 9608929. DOI: 10.1186/s12884-022-05075-2.

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