Echogenicity, pregnancy and the pelvic floor, an observational ultrasound study

Abstract

The pelvic floor provides support to the pelvic organs. Pregnancy and childbirth are strongly associated with pelvic floor dysfunction, leading to pelvic floor disorders such as pelvic organ prolapse and urinary incontinence. By the use of transperineal ultrasound we are able to visualize the puborectalis muscle, one of the most important muscles of the pelvic floor. The most common finding in women with stress urinary incontinence (SUI) is hypermobility of the urethra. Normal urethral function depends not only on urethral support but also on the internal urethral closure mechanism. The mid-urethral mean echogenicity of our study group with the pelvic floor at rest was significantly higher during pregnancy as compared to 6 months after delivery. The most likely explanation is that pregnancy, with its increased levels of progesterone, induces an increase in fat storage and collagen in muscle tissue. A large hiatal area is associated with SUI, which raises the question if this is related to structural abnormalities of the puborectalis muscle. Women with SUI after delivery had a significant higher mean echogenicity of the puborectalis muscle (MEP) as compared to continent women. This indicates that the ratio between muscle cells and extra cellular matrix (ECM) shifted towards the ECM. Scar tissue formation, which will represent itself as a higher echogenicity, is associated with a loss of contractility function of the muscle. If the increase in ECM in the puborectalis muscle indeed indicates that this will compromise its contractile function, its contribution to the urethral support may be compromised. Previously we studied the possible association between ultrasound parameters of the pelvic floor during pregnancy and mode of delivery. We were unable to confirm the previous results of a smaller MEP and hiatal transverse diameter and area during contraction at 12 weeks’ pregnancy in women with a caesarean section due to failure to progress. Trauma during delivery is known as one of the most important causes of pelvic floor disorders. Little is known about normal recovery of the pelvic floor in the first weeks after vaginal delivery. A better understanding is of importance when considering early interventions improving recovery. Recovery of the hiatal dimensions at rest and contraction, back to early pregnancy values, was completed within the first 3 weeks after vaginal delivery. Recovery of the contractility to early pregnancy state occurred between 6 and 12 weeks after delivery. The hiatal area on maximum Valsalva maneuver and the difference between rest and Valsalva, distensibility, remained increased during the complete follow-up period of 24 weeks. Persistent enlargement of the hiatal area on Valsalva and increased distensibility 24 weeks after delivery, implicate that there are persistent structural changes in the puborectalis muscle after delivery. The MEP is significantly lower directly after delivery compared to the MEP during pregnancy, slowly increasing up to 24 weeks after delivery, but not reaching pregnancy values. The sharp decrease in MEP directly after delivery is most likely the resultant of edema and (micro)hematoma due to stretch trauma after delivery, since fluid appears dark on the ultrasound image.