Transvaginal three-dimensional ultrasound: a method of studying anal anatomy and function

The Role of Transperineal Ultrasound for the Assessment of the Anorectal Angle and Its Relationship with Levator Ani Muscle Avulsion

The relationship between the anorectal angle (ARA) and the levator ani muscle (LAM) is well known. In this study, we aimed to demonstrate that the ARA changes when LAM avulsion occurs after vaginal delivery. This was a secondary, observational retrospective study with data obtained from three previous studies. Using transperineal ultrasound, the presence of avulsion was assessed when abnormal insertion of the LAM was observed in three central slices. In addition, the ARA was assessed in the midsagittal plane (at rest, in Valsalva and at maximum contraction) as the angle between the posterior border of the distal part of the rectum and the central axis of the anal canal. The ARA was higher in patients with bilateral LAM avulsion than in patients without LAM avulsion at rest (131.8 ± 14.1 vs. 136.2 ± 13.8), in Valsalva (129.4 ± 15.5 vs. 136.5 ± 14.4) and at maximum contraction (125.7 ± 15.5 vs. 132.3 ± 13.2). The differences between both groups expressed as the odds ratio (OR) adjusted for maternal age were 1.031 (95% confidence interval (CI), 1.001–1.061; p = 0.041) at rest, 1.036 (95% CI, 1.008–1.064; p = 0.012) in Valsalva and 1.031 (95% CI, 1.003–1.059; p = 0.027) at maximum contraction. In conclusion, LAM avulsion produces an increase in the ARA at rest, during contraction and in Valsalva, especially in cases of bilateral LAM avulsion.

Development of the maternal anal canal during pregnancy and the postpartum period: a longitudinal and functional ultrasound study

OBJECTIVES

Normal anatomical and physiological development of the maternal anal canal during and after pregnancy has been documented scarcely. We aimed to study the position and volume of the anal canal, during and after pregnancy, in women without previous delivery.

METHODS

This was a longitudinal study in which transvaginal three-dimensional ultrasound was used to measure anatomical structures in the anal canal during rest and squeeze in 23 nulliparous women. The total anal canal volume (ACV), anorectal curvature (ARC), anovaginal angle (AVA) and anal canal length were determined at 18, 28 and 36 weeks of pregnancy and at 3 months postpartum.

RESULTS

Total ACV at rest increased from a mean of 10.17 cm(3) at 18 weeks to 12.37 cm(3) and 12.21 cm(3) at 28 and 36 weeks, respectively (P = 0.001 and P = 0.010 vs. first measurement). For anal canal length, the corresponding mean measurements were 3.91 cm, 4.07 cm (P = 0.13) and 4.21 cm (P = 0.017). Postpartum, the mean total ACV was 10.86 cm(3) and length was 3.90 cm (P = 0.10 and P = 0.70 vs. first measurement). No significant changes were observed in ARC and AVA during or after pregnancy. Compared to at-rest status, the anal length significantly increased on voluntary squeeze (P = 0.007, 0.007, 0.022 and 0.004 at the four time points), while no differences in total ACV were observed. In mid-pregnancy AVA significantly increased during squeeze (P = 0.006 and 0.002 at weeks 18 and 28, respectively).

CONCLUSION

Anal canal length and total ACV increase during pregnancy in women without previous delivery. Voluntary squeezing elongates the anal canal and increases the angle formed with respect to the direction of the vagina. During postpartum involution, the characteristics of the anal canal revert to those observed at 18 weeks of pregnancy.

Three-dimensional transperineal ultrasound findings associated with anal incontinence after intrapartum sphincter tears in primiparous women

OBJECTIVE

Three-dimensional transperineal sonography (3D-TPS) performed in women following third- or fourth-degree intrapartum tears repaired with the overlapping technique demonstrates characteristic signs. The aim of this study was to investigate the correlation of these signs with clinical complaints of incontinence.

METHODS

This was a prospective observational study. Sixty primiparous women underwent 3D-TPS 3-42 (mean, 10.6) months after surgical repair of third- or fourth-degree postpartum sphincter tears with the overlapping technique and were evaluated for clinical degree of incontinence using the St Mark's Incontinence Score (SMIS) questionnaire. The following signs were assessed on 3D-TPS: interruption of the internal anal sphincter or external anal sphincter, 'half moon' sign, changes in the mucosal folds and thickening of the external anal sphincter in the area of sphincter repair. As a comparison group, 27 primiparous women after normal vaginal delivery, without clinically recognized anal sphincter tears, were evaluated similarly, 3-37 (mean, 9.9) months postpartum.

RESULTS

Abnormal sonographic signs were apparent in 35 (58.3%) of 60 women in the study group, and 39 (65%) of 60 had some clinical complaints of incontinence 3-42 months after delivery, most of a mild degree. Higher SMIS results were found in women of the study group than in those of the comparison group (mean (SD) 2.80 (0.481) vs. 1.15 (0.365); P = 0.018). The rates of incontinence were similar between the women in the study group with normal ultrasound findings and the women in the comparison group (9/25 vs. 10/27; relative risk (RR) = 0.97, 95% CI, 0.47-1.97).

CONCLUSIONS

Sonographic signs of anal sphincter tear and repair had disappeared at follow-up examination in almost half of the patients, and therefore this examination should be deferred from the early postpartum period. A substantial proportion of women report some complaint of incontinence after sphincter repair, most of a slight degree. Such complaints are associated with abnormal 3D-TPS findings at follow up, while in women with a normal 3D-TPS scan the rate of incontinence complaints is similar to that in women after normal delivery.