In the 35 women who participated in this study, perianal ultrasound (PAUS) was a reliable means of diagnosing anorectal function and disorders. Reproducibility of PAUS volumes was good, allowing two independent examiners to perform her PAUS examination with similar her 3D/4D volumes. Her EAS and IAS sphincter thicknesses on PAUS showed differences between the 6 o’clock and her 12 o’clock positions, with greater thickness at the 12 o’clock position. Images of the anal canal showed no difference in sphincter thickness at rest and contraction in EAS and IAS. IAS indicates that muscle contractions are isovolumic. During contraction, the vertical diameter decreases and becomes elliptical (Fig. 7).
Our results showed that the subjective test DRE is reproducible by different examiners.
The DRESS shrinkage score was used to compare PAUS and DRE. Although the lack of inclusion of the DRESS resting score should be discussed, we found that the DRESS resting score was independent of and uncorrelated with the patient’s contraction score. Comparing PAUS and DRE showed a non-significant negative correlation between vertical diameter change distance under contraction in PAUS and DRESS contraction score. Interestingly, we found that large changes in vertical diameter values during contractions measured with PAUS volumes did not correlate with stronger contraction tone in DRE. Indeed, shorter changes in vertical contractions were associated with stronger contraction sounds in the DRE. This assumes that the PAUS vertical diameter difference is not a reliable parameter for assessing rectal tone and sphincter contraction.
Contraction can only be visualized by a change in vertical diameter and disappearance of mucosal rosettes in the ultrasound volume. This supports our hypothesis that the pelvic floor muscles have a major influence on the voluntary contraction that pulls the anal canal cranially.
The difference in sphincter thickness in EAS and IAS between the 6 o’clock and 12 o’clock positions in PAUS is interesting because the assumption is that sphincter thickness is constant at all positions. Our probe is placed in the anal opening and in the ventral direction it is tilted 10°-20° and the axis of the plane is rotated. Assume that the anal canal is visualized in an oblique plane because it is not a rigid canal and the probe is tilted. Although the horizontal diameter was larger than the vertical diameter at rest and during contraction, only the contraction values showed a significant difference. Rotation of the probe and the puborectalis muscle with its activity in voluntary contraction affect the vertical diameter.
The EAS and IAS thicknesses measured at the 12 o’clock position are consistent with the results of other studies. The results were comparable to those reported by Rao. [1]. Although Beets-Tan et al.’s report measured at the 4 o’clock position and he used EAUS, there was good agreement between our results and Beets-Tan et al.’s report. Ta. [18]. West et al. Using 3D-EAUS, we found that the thickness of the EAS at the 6 o’clock and his 12 o’clock positions was completely opposite to ours. [19]. Differences may be due to the defined measurement location and type of examination. In terms of actual measurements, Williams et al. using EAUS and eaMRI measured at least twice as many values compared to ours.Differences with our study may be due to measurement of horizontal line position at the level of the median canal, younger patients, and endoanal probe [20]. Because the EAUS probe straightens the sphincter, which changes its structure, it is questionable whether EAUS and PAUS can be compared reliably. Furthermore, EAUS probes exist in different sizes, which may also explain the heterogeneous results.
Although there is no difference in the muscle thickness of the IAS, the longitudinal diameter becomes shorter during contraction and changes into an oval shape, which is thought to be due to external influences in the surrounding area (pelvic floor, especially the puborectalis muscle) that cause this change. You can . The anal canal forms an angle of approximately 90 degrees with the axis of the rectum at rest. This angle becomes sharper during voluntary squeezing and blunter during defecation. [1]. Pelvic floor muscles, such as the EAS and puborectalis muscles, are among the few striated muscles in the body that activate spontaneously during rest and never fully relax. [21]. At rest, the anus is closed by the tonic activity of the smooth muscle IAS. During contraction maneuvers, the EAS and puborectalis muscles strengthen this barrier because the patient is unable to fully contract the anal and pelvic floor muscles by separating the muscles. The sling of the puborectalis muscle around the rectum pulls the axis of the vertical diameter forward during contraction, resulting in an increase in the anorectal angle and a change in shape. [1, 22].Other studies, e.g. Olsen et al. EAUS measurements found no difference between rest and contraction [23]. This may be explained by the fact that the EAUS probe has a round and rigid structure that cannot be modified by changes in the composition of the surrounding muscles. Conversely, this may lead to adapting the shape of the muscle to the rigid structure of the endoanal ultrasound probe.
Compared to ultrasound, DRE is a subjective test and requires some experience to provide an accurate score of sphincter tone, but as our results show, it is also reproducible by different examiners. . Previous studies have found that DRE is an excellent and reliable test with a moderate to highly positive correlation with sphincter tone objectively measured by anorectal manometry. [15, 24].
Although PAUS shows that the anal canal changes from a circular to an oval shape during contractions, the examiner performing the DRE can only detect circular contractions around the finger. Taverner et al. We showed that various activities, such as vocalization, increased intra-abdominal pressure, and voluntary contraction of the pelvic floor muscles, increased the activity of the EAS and puborectalis muscles. [25]. DRE increases the sphincter tone reflex by touching the perianal skin through very sensitive modulation. [21, 25].
Taverner et al. and Widener et al. Electromyography showed tonic contraction of the puborectalis muscle and EAS. The DRU increased sphincter tone during skin contact and canal expansion, which decreased despite the presence of fingers. Voluntary contractions resulted in higher firing rates of motor units in the EAS and puborectalis muscles, but firing rates were higher in the puborectalis muscles. Their findings showed that the levator ani muscle has larger and more easily recruited motor units than the EAS. [25, 26].
The major difference between these methods is that DRE is a subjective impression, whereas PAUS measurements are more objective. The comparison of methods used a scoring system of subjective impressions and objective measurable distance changes. DRESS-Score is an attempt to give subjective impressions a more objective and comparable value. However, the measurement of ultrasound volume contains a slight subjective element, as the examination and measurement always depend on the examiner. The difference between the tests is that DRE determines the function of the sphincter muscle through muscle tone, whereas PAUS shows the sphincter muscle and its surrounding structures. I performed similar operations with both methods.
DRE is used clinically to obtain impressions of muscle tone and palpate abnormalities. A disadvantage of DRE is that the subjective impression of muscle tone can only be documented in a score, making accurate comparisons difficult at follow-up visits and providing no biofeedback to the patient.
The potential clinical value of PAUS is to be a standardized screening tool to detect asymptomatic or symptomatic sphincter defects, or postpartum when FI symptoms occur.Early detection of lesions may improve patient outcomes [8, 27]. PAUS may be a fundamental diagnostic tool to fill memory gaps in the history of perineal lacerations or to demonstrate persistence of current symptoms when no history of perineal lacerations is known . Additionally, PAUS may help determine potential factors leading to FI, such as structural sphincter defects, prolapse, hemorrhoids, and fecal impaction. [8, 27]. PAUS can be used to document volume, improving comparability during follow-up visits. Another potential clinical value of PAUS could be the possibility of providing biofeedback to patients about the structure and function of the anal sphincter. It may also be helpful in counseling birth planning after a previous grade III or IV perineal tear.
PAUS and DRE are perfect additional tests to improve the examiner’s 4D impression. PAUS, like PUS, is widely available and inexpensive, and apparently it is better tolerated by patients than DRE or EAUS. [8, 11, 12].
The mean age in our study (57 years) is not representative of the entire population, but reflects the age of patients suffering from FI. [3, 4]. The age range of research subjects is wide. Further studies would be improved by more homogeneous groups to exclude the influence of variables such as age and mode of birth in order to better compare patients and measurements. The literature contains various statements about the influence of age on sphincter thickness. Starck et al. Murad-Regadas et al. found no correlation between age and EAUS sphincter measurements. We found that the IAS was thicker in older nulliparous women compared with younger nulliparous women, but no effect of age on sphincter thickness was found in women who delivered vaginally or by caesarean section. [28, 29]. Frudinger et al. In nulliparous women, there was a significant correlation between age and sphincter thickness for EAUS, a positive correlation for IAS, and a negative correlation for EAS. [30]. Further studies should investigate and evaluate this issue using PAUS, as current data are mostly available with EAUS data.
Our study is limited by the fact that we only included patients without sphincter defects on ultrasound and had a small sample size. No preliminary evaluation of patient groups was performed in our study. In the future, a more homogeneous group of patients should be defined before starting measurements to minimize the number of excluded patients. Improvements in ultrasound technology also help improve sample quality. Surveys may be too long, which minimizes patient motivation to complete them. A short survey could help improve this. In general, more research and awareness is needed about the relevance and importance of questionnaire responses in medical research.
Small sample size reduces clinical power. Studies with larger sample sizes are needed to confirm our findings. We view our research as providing a basis for further research. Clinically, there are many aspects of the physiology and complexity of the pelvic floor that are not fully understood, and this provides clues for future research to address and explore this topic.
Another limitation is that only one examiner performed the measurements on the PAUS images.