Descending perineum syndrome was observed in patients with chronic constipation and was first defined as a relaxation of the pelvic floor by Parks et al. [1] in 1966. While the cause of increased perineal descent is believed to be excessive straining upon defecation, excessive straining causes the anterior rectal wall to protrude towards the anal canal, in turn inducing incomplete defecation and a weakness of the pelvic floor muscle. In addition, such incomplete defecation results in more excessive straining, and the weakened pelvic floor results in increased perineal descent, resulting in a vicious cycle [1, 2]. Other authors have noted that the abnormal descent of the perineum not only causes constipation, but also frequently causes fecal incontinences, anal pain, and other symptoms [3-5].

For the management of descending perineum syndrome, surgical treatment has shown little efficacy, leading to the administration of various forms of conservative treatments, such as changes in diet, regulating defecation habits, use of purgatives, and biofeedback treatment. According to the study of Hur et al. [6], biofeedback has an approximately 92% success rate, shows symptomatic improvement and can be considered to be the most suitable method of treatment. In addition, D'Amico and Angriman [7] argued that a complete recovery from descending perineum syndrome was difficult to expect and that treatment should focus on improving symptoms according to the individual patient. From such a perspective, an analysis of the causes of the descending perineum syndrome is important. Causes in women are known to be associated with the number of vaginal deliveries, cases of obstructed labor, and anorectal surgery [8, 9] while rectoceles and intussusceptions are also known to induce excessive straining, causing constipation and resulting in a descent of the perineum. In addition, Pucciani et al. [10] showed that a total abdominal hysterectomy was also associated with perineal descent in women. Within such a context, we aimed to investigate the association between various factors and increased perineal descent in women.

Descending perineum syndrome, one of the functional causes of idiopathic chronic constipation, can be understood to be a relaxation of the pelvic floor resulting from excessive straining upon continuous defecations. Consequently, while this is a cause of constipation, it reversely is also a phenomenon furthered due to chronic constipation. Excessive perineal descent also results in anorectal pain or fecal incontinence.

The degree of perineal descent can be measured by administering defecography and defines the perpendicular distance from the anorectal connection, in other words, from the contact point where the distal rectal posterior line and the central axis of the anus canal meet to the pubococcygeal line [11, 12]. However, as the measurement of the anorectal angle or perineal descent within defecography has poor reproducibility and differences exist between examiners, objective measurement through identical standards is important [13]. In addition, the definition of a significant increase of the perineal descent differs by author. In the case of Landmann and Wexner [14], an abnormal increased perineal descent was diagnosed in instances where the resting phase was over 4 cm and the dynamic perineal descent was over 3 cm, and Parks et al. [1] diagnosed a significant increase when the resting phase was over 3 cm and dynamic perineal descent was also over 3 cm while Kim et al. [15] diagnosed cases of significant increase when the resting phase was over 5 cm and the dynamic perineal descent was over 4 cm.

The perineal descent observed in a defecography has generally been seen as a phenomenon occurring due to various diseases that cause pelvic outlet obstruction rather than a disease occurring independently [3, 16], and clear explanations of descending perineum syndrome or related factors have yet to be given. Many previous studies attribute the cause to a weakening of the pelvic floor caused by external damage to the perineum or by trauma to the pudendal nerve caused by delivery in women [9, 14, 17, 18]. In addition, there have also been opinions that it is related to surgical history, such a hysterectomy and repair of rectoceles and cystoceles [18]. In the present study, the association between the past history of patients and the amount of perineal descent was investigated. Increasing age, increasing number of vaginal deliveries, and increasing resting-phase perineal descent showed a statistically significant association, but surgical history did not show any correlation. Within research on association with dynamic perineal descent, while a relationship was shown with increasing age, no relationship was shown with number of vaginal deliveries or surgical history. In addition, Ahn et al. [19] reported that defecography for patients with defecation disorders showed various overlapping findings, particularly numerous cases of excessive perineal descent being accompanied by rectoceles, non-relaxing puborectalis or sigmoidoceles. In that study, however, no such significant relationships were discovered. The results of the present study showed a statistically-significant correlation between resting-phase perineal descent and resting anorectal angle while a statistically significant increase in resting-phase perineal descent was observed in patients with rectoceles or intussusceptions. On the other hand, the increase in dynamic perineal descent had no statistically significant relationship with diagnosis found through defecography except sigmoidoceles.

In addition, regarding the hypothesis that there was a relationship between the neuropathy of the puborectalis and descending perineum syndrome, the increased perineal descent might have occurred due to a weakening of the pelvic floor caused by perineal nerve damage. Research findings have indicated that patients showing signs of descending perineum syndrome exhibit nerve conduction delays on pudendal nerve terminal motor latency (PNTML) tests and that these findings have a significant relationship [20], but other authors have concluded the opposite by arguing that there is no significant relationship [21]. In addition, Lee and Park [17] suggested that increased perineal descent could be due to pudendal nerve damage following vaginal delivery, but abnormalities as shown on PNTML test was recovered within 2 months and increased perineal descent could continue for 6 months. The findings of the two tests could be different depending on the timeframe of clinical observation.

The PNTML test was not included in the present study. However, the correlation between anal pressure and nerve or sphincter damage was investigated. The resting-phase perineal descent had no relationship with either the resting or the squeezing anal pressure. However, the dynamic perineal descent had a significant relationship with the resting anal pressure. This result suggests that nerve injury could have an effect on dynamic perineal descent, but the reason for the different resting perineal descents is not clear.

The cause of increased perineal descent, excessive straining during defecation, weakened perineal muscle and excess perineal descent, are believed to make a vicious cycle. During the cycle, the perineal muscle would be weakened more, and fecal incontinence would be present as a late symptom of the cycle. Therefore, we suppose that patients with symptoms of fecal incontinence may have larger perineal descent. In the present study, the mean resting-phase perineal descent of patients with fecal incontinence was larger than it was for patients with other symptoms, but the differences were not statistically significant.

As mentioned before, rather than occurring independently, most cases of increased perineal descent are accompanied by various diseases that cause the onset of defecation disorder. As such, most forms of treatment focus on easing the symptoms of defecation disorder or remedying diseases believed to be a direct cause of the increased perineal descent rather than on the increased perineal descent itself. Cundiff et al. [22] reported that within descending perineum syndrome patients with accompanying vaginal prolapse, the results of clinical observations of 11 patients who underwent abdominal sacral colpoperineopexy showed improved symptoms in 8 patients, with perineal descent returning to normal ranges. Most studies, however, have argued that descending perineum syndrome must be improved through conservative treatment rather than surgical fixation and have reported biofeedback to be particularly effective. Such efficacy of biofeedback resulted in improved symptoms regardless of constipation or fecal incontinence [23-25]. However, because the effects of such treatments are clear in the early stages where the increase in perineal descent is not severe, early treatment of the disorder through adequate examinations of patients with defecation disorder is important [18]. However, biofeedback focuses on improving symptoms rather than being a fundamental treatment. Consequently, studies on more fundamental forms of treatment are required for patients who have continuing or recurring symptoms after treatment.

The focus of the present study was to reveal factors associated with the increasing perineal descent frequently found in female patients with defecation disorders. The results of the study showed a statistically significant difference in factors associated with increased resting and dynamic perineal descent. The results show that with a better understanding of the pathophysiology of descending perineum syndrome, a fundamental method of treatment can be achieved. Additional studies are necessary to address factors not included in the present study so that a better understanding of relevant medical practices can be achieved.