Endosonography of the anal sphincter in women of different ages and parity.

Objectives
To obtain reference data representative of normal findings at anal endosonography in pregnant and non-pregnant women. To determine intraobserver and interobserver agreement in the detection of endosonographic anal sphincter defects in asymptomatic women.

Methods
Twenty-five non-pregnant nulliparous women and 25 non-pregnant parous women (age range, 20-67 years) and 47 pregnant women (age range, 21-39 years) underwent anal manometry and anal endosonography. The endosonographic internal and external sphincter thickness and sphincter length were measured online. Endosonographic sphincter defects were measured and classified offline from videotapes by two independent examiners using an endosonographic defect score ranging from 0 (no defect) to 16 (maximal defect), the score taking into account the location and the longitudinal and circumferential extension of the defect.

Results
Endosonographic sphincter thickness and length did not differ between non-pregnant nulliparous and parous women and did not change substantially with age. The anal sphincter was thicker and the anal resting pressure area and manometric sphincter length were greater in pregnant than in non-pregnant women of the same age (20-39 years). There was good intra- and interobserver agreement with regard to detection of endosonographic anal sphincter defects (kappa 0.70). Eighteen (19%) women had endosonographic sphincter defects but in only four (4%; 4/97) cases were they moderate or large (defect score, 7-10). Ten (20%) of the non-pregnant women reported minor gas incontinence and one reported minor incontinence for both gas and liquid stool. The frequency of incontinence did not differ between women with and without sphincter defects.

Conclusions
Reference data representative of normal findings at anal endosonography have been established for non-pregnant women and for nulliparous women in the third trimester of pregnancy. Small endosonographic sphincter defects and minor gas incontinence are common in women without known sphincter trauma. They seem to be unrelated to each other and may be regarded as normal variants.