Full thickness rectal prolapse (FTRP) is a heterogeneous condition with a wide range of disease presentations and clinical findings. While some patients report FTRP exclusively during defecation, others may experience it during routine activities or persistently. We hypothesize that patients with defecation only FTRP have distinct physiological and radiologic characteristics compared to the rest of patients with FTRP.

We conducted a retrospective analysis of a prospectively maintained IRB-approved registry of patients undergoing surgical evaluation from 2017 to 2023. We included all females with FTRP, and compared the differences between women with defecation only FTRP and women who have FTRP during other times (walking, exercise, and/or all the time). Demographic information was extracted from the medical record. Self-reported RP symptoms, obstructed defecation scores (ODS) and Wexner fecal incontinence scores were collected on patients’ initial visit. MR defecography (MRD) and anorectal manometry (ARM) were recommended and ordered as part of the preoperative evaluation. 
 
MRD was performed on an MRI system with patients self-administering enema prior to arrival [1]. Standard measurements were collected – which includes pelvic floor linear measurements at rest and during defecation, anterior and middle compartment anatomy, and levator ani muscle characterizations. Estimated levator ani subtended volume (eLASV), a recently developed novel surrogate measurement for pelvic floor laxity and pelvic organ prolapse, was calculated based on a previously published formula utilizing measurements from H line, M line and levator hiatus width [2]. Descent of the rectum through the anal canal on MRD was assessed as intrarectal, intra-anal/external. High resolution anorectal manometry (ARM) and Balloon Expulsion Test (BET) were performed using a 2D manometry catheter following a standard protocol [3]. Differences between the 2 groups were evaluated by Fisher’s exact test for categorical variables and Wilcoxon test for continuous variables. MRD predictors for defecation during other times were evaluated by multivariable logistic models. Models were adjusted with age, prior prolapse repair history, obstetric history and BMI.

Of 378 patients in our registry, 297 patients met our inclusion criteria: 147 (49%) women reported FTRP with defecation only, and 150 (51%) women reported FTRP during other times. We found that women with defecation only FTRP were younger (median [IQR] age: 64 [48, 74] vs. 71.5 [63, 79]); baseline ODS score was higher in women with defecation only FTRP (median [IQR]: 9 [5, 13] vs. 7 [4, 10], p<0.001), while Wexner score was higher in women with FTRP during other times (median [IQR]: 12 [3, 16] vs. 15 [12, 18], p<0.001). Women with defecation only FTRP were more likely to have symptoms longer than 6 months (86% vs 73%, p=0.006). Additional patient characteristics including comorbidities and obstetrics history were comparable and are included in Table 1. 
 
Among the full cohort, a sub-cohort of 117 patients were able to complete an MRD (Table 2a). For linear measurements of the pelvic floor, we found that women with defecation only FTRP have shorter H line at rest (median [IQR], cm: 6 [5.3, 6.7] vs. 6.5 [5.7, 7.1], p<0.001), more acute resting anorectal angle (median [IQR]: 109 [93, 120] vs. 118 [102, 130], p=0.02), and lower resting width of levator hiatus (median [IQR], cm: 6 [5.3, 6.7] vs. 6.5 [5.7, 7.1], p<0.001). Women with defecation only FTRP also have a smaller eLASV (median [IQR] cm3: 27 [17, 50] vs. 42 [27, 58], p=0.008). There are no significant differences between the distribution of type of rectal prolapse between the two groups, with similar percent of patients categorized as intra-anal RP (78% vs. 88%, p=0.21). Women with defecation only FTRP are less likely to have an open anal canal at rest (31% vs. 58%, p=0.004) and more likely to have a rectocele present (71% vs. 50%, p=0.02). There are no significant differences observed between the 2 groups for anterior and middle compartment anatomical structures and levator ani muscle characterization.
 
Among the full cohort, a sub-cohort of 67 patients were able to complete an 2D ARM (Table 2b). Women with defecation only FTRP had higher resting pressures (​​median [IQR]: 33 [16, 53] vs. 20 [16, 27], p=0.03), longer duration of sustained squeeze (median [IQR], sec: 11 [5, 17] vs. 6 [4,10], p=0.04), and higher intrarectal pressure during attempted defecation (median [IQR]: 44.4 [29.6, 59.5] vs. 33.2 [27.3, 41.0], p=0.04). The 2 groups had similar length of high-pressure zone, squeeze pressures, and percent of anal relaxation during attempted defecation. The 2 groups took similar time to expel the balloon in the BET. 
 
In multivariable models, higher H line at rest (aOR [95% CI]: 1.5 [1.0, 2.2]) and during defecation (aOR [95% CI]: 1.4 [1.1, 1.8]), as well as higher eLASV were associated with increased odds of FTRP during other times (Table 3).

In this cohort study of female FTRP patients, we characterize the pelvic floor biomechanics of patients with different symptom timing and report novel findings of notable MRD and ARM characteristics in this heterogeneous condition. Compared to women with FTRP during other times, women with defecation only FTRP are younger and more likely to have symptoms for more than 6 months before seeking surgical evaluation.  Women with defecation only FTRP showed significantly less pelvic floor laxity on MRD, evident by significantly smaller hiatus length (H line) and width and therefore smaller levator hiatus bowels (eLASV). H line at rest, H line during defecation and eLASV were associated with the timing of defecation symptoms. A similar trend is also observed in the ARM data: women with defecation only FTRP have more preserved anorectal function, which is indicated by higher resting sphincter pressure, longer sustained squeezes and higher intra-rectal pressure during attempted defecation.  

Both physiologic test results suggest FTRP during other times is possibly a later stage of disease presentation compared to FTRP with defecation only; notably, eLASV may be helpful for indicating state of pelvic floor deconditioning and disease progression.

Patients with defecation only FTRP have distinct clinical characteristics and pelvic biomechanics: H line at rest and during defecation and larger pelvic volume could each predict the risk of more sustained FTRP. The younger age of patients with defecation only FTRP along with more severe ODS symptoms with preserved pelvic motions and anorectal pressures may suggest an early stage phenotype of FTRP.  Future longitudinal research will be needed to identify the risk factors associated with progress to more sustained FTRP and also the role for early intervention in this group of FTRP patients.

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Wyman AM, Rodrigues AA, Hahn L, et al. Estimated levator ani subtended volume: a novel assay for predicting surgical failure after uterosacral ligament suspension. Am J Obstet Gynecol. 2016;214(5):611.e1-611.e6. doi:10.1016/j.ajog.2015.11.005
Neshatian L, Williams MJOU, Quigley EM. Rectal Distension Increased the Rectoanal Gradient in Patients with Normal Rectal Sensory Function. Dig Dis Sci. 2021;66(7):2345-2352. doi:10.1007/s10620-020-06519-5

Continence 12S (2024) 101682
DOI: 10.1016/j.cont.2024.101682