Obstructive defecation: a failure of rectoanal coordination

Objective: The pathophysiology of obstructive defecation is unclear. We investigated whether impaired rectoanal coordination causes obstructive defecation and if this dysfunction can be corrected by biofeedback therapy.
Methods: We prospectively studied 25 healthy subjects and 35 consecutive patients with constipation (>1 year) with anorectal manometry and balloon expulsion test. Symptoms were assessed from diary cards. Patients found to have obstructive defecation were offered biofeedback therapy. After treatment, their defecation dynamics and symptoms were reassessed.
Results: Eighteen patients had obstructive defecation and 17 had normal defecation dynamics (nonobstructive). Five normals (20%) exhibited obstructive pattern but only one failed to expel balloon. In the obstructive group, during straining, the intrarectal pressure and defecation index were lower (   p < 0.05  ), and anal residual pressure was higher (   p < 0.01  ) when compared with the nonobstructive group or normals. After biofeedback therapy, the intrarectal pressure and defecation index increased (   p < 0.02  ) and anal residual pressure decreased (   p < 0.001  ); stool frequency, degree of straining, and bowel satisfaction scores improved (   p < 0.05  ); 67% stopped laxatives and 11 patients discontinued stooling with digitation.
Conclusion: Patients with obstructive defecation showed impaired rectal contraction, paradoxical anal contraction, or inadequate anal relaxation. These features suggest that rectoanal coordination was impaired. Biofeedback therapy rectified these pathophysiological disturbances and improved constipation.     

Pathophysiology and role of biofeedback therapy in solitary rectal ulcer syndrome

BACKGROUND: Solitary rectal ulcer syndrome (SRUS) is a behavioral disorder whose pathophysiology is incompletely understood. Likewise, its treatment, particularly the role of biofeedback therapy (BT) is unclear. AIM: To evaluate anorectal function and morphology and to assess efficacy of BT. METHODS: Eleven patients (8f) with refractory SRUS underwent symptom assessments, anorectal manometry, defecography, balloon expulsion test, and sigmoidoscopy. Physiological tests were also performed in 15 (11f) healthy controls. Subsequently, SRUS patients underwent biofeedback treatment. Symptoms and manometry were reassessed. RESULTS: Nine (82%) patients exhibited dyssynergia ( p < 0.001). Rectal sensory thresholds were decreased (p < 0.04). After biofeedback, straining effort and stool frequency decreased ( p < 0.05), and bowel satisfaction score (VAS) improved ( p < 0.001). Digital maneuvers were discontinued by all five patients and bleeding stopped in 56%. The defecation index increased ( p < 0.05), dyssynergia normalized, and balloon expulsion time decreased ( p < 0.05). There was complete healing in 4 (36%), > or =50% healing in 2 (18%), and <50% healing in 4 (36%) patients. CONCLUSIONS: SRUS associated with excessive straining, digital disimpaction, rectal hypersensitivity, dyssynergic defecation, and prolonged evacuation. BT may improve symptoms and anorectal function and facilitate healing.     

Effect of biofeedback therapy on anorectal physiological parameters among patients with fecal evacuation disorder

Background

Though biofeedback therapy is often effective in patients with fecal evacuation disorder (FED), a common cause of chronic constipation (CC) in tertiary practice, data on anorectal physiological parameters following it are scanty.

Methods

Consecutive patients with FED with CC diagnosed by abnormalities in at least two of the three tests (anorectal manometry, defecography, and balloon expulsion test [BET]) undergoing biofeedback (two sessions per day, 30 min each, for 2 weeks) during a 3-year period were analyzed. Clinical evaluation, anorectal manometry (ARM), and BET were performed at the beginning and after biofeedback.

Results

Incomplete evacuation 42/43 (98%), straining 40/43 (93%), and feeling of outlet obstruction 35/43 (81%) were the most common symptoms among these 43 patients (median age 44 years, range 18–76, 30 [71%] male). All the three tests (defecography, BET, and ARM) were abnormal in 17 (40%) patients and the others had two abnormal tests. Improvement in physiological parameters was noted following biofeedback (median residual anal pressure during defecation 99 mmHg (range 52–148) vs. 78 mmHg (37–182), p = 0.03; maximum intra-rectal pressure 60 mmHg (90–110) vs. 76 mmHg (31–178); p = 0.01; defecation index 1.1 (0.1–23.0) vs. 3.2 (0.5–29.0); p = 0.001). Dyssynergia on ARM and BET got corrected in 22/34 (65%) and 18/30 (60%) patients. At a 1-month follow up, 23/37 (62%) patients reported satisfactory symptomatic improvement.

Conclusions

Biofeedback not only improves symptoms but also anorectal physiological parameters in patients with FED.

     

Effects of biofeedback on obstructive defecation--reconditioning of the defecation reflex?

Twenty two patients with obstructive defecation were recruited for relaxation training by domiciliary self regulatory biofeedback. Each patient served as his or her own control for anorectal and proctographic assessments. Biofeedback training improved the obstructive symptoms of the patients and showed significant change in various parameters related to the obstructive defecation syndrome. As examined by isotope dynamic proctography: the defecation rate (% of evacuation/defecation time) was significantly increased (p < 0.05), the anorectal angles at rest and during attempted defecation were made more obtuse (p < 0.05), and the pelvic floor movements were made more dynamic on voluntary contraction of the anal sphincter (p < 0.03). The external anal sphincter electromyographic voltage recorded during defecation was significantly reduced (p < 0.0005) as was the surface anal plug electromyographic electrode voltage (p < 0.0001), which was associated with a greatly reduced anismus index (p < 0.0001). The rectal sensation was improved (p < 0.05), concomitantly. Biofeedback thus improves the defecation act in patients suffering from inappropriate contraction of the pelvic floor and sphincter musculature. Furthermore, this study has shown that biofeedback objectively influences the defecation reflex leading to an improved quality of higher control of bowel function.     

Investigation of the pathophysiology of fecal seepage

BACKGROUND AND AIM:   Unintentional seepage of stool without awareness is common but its pathophysiology is poorly understood. Our aim was to examine the underlying mechanism(s) for fecal seepage.
METHODS:   We evaluated prospectively 25 patients with fecal seepage, by performing anorectal manometry, balloon expulsion, saline infusion, pudendal nerve latency tests, and symptom assessments and compared their data with 26 fecal incontinence patients and 43 healthy controls.
RESULTS:   Predisposing factors for fecal seepage were back injury (7), obstetric injury (6), hemorrhoidectomy (3), pelvic radiotherapy (1), and unknown (8). In the seepage group, the resting and squeeze sphincter pressures were lower ( p < 0.02) than healthy controls, but higher ( p < 0.002) than incontinent group. During straining, the intrarectal pressure and defecation index were lower ( p < 0.05) in the seepage group compared to controls; 72% showed dyssynergia and balloon expulsion time was prolonged ( p < 0.01). Threshold for first rectal sensation was impaired ( p < 0.002) in the seepage group compared to controls and incontinent group. The seepage group retained more ( p < 0.001) saline than the incontinent group but pudendal nerve latency time was impaired ( p < 0.05) in both patient groups compared to controls.
CONCLUSIONS:   Anal sphincter function and rectal reservoir capacity were relatively well preserved but most patients with seepage demonstrated dyssynergia with impaired rectal sensation and impaired balloon expulsion. Thus, incomplete evacuation of stool may play a significant role in the pathogenesis of seepage.     

Manometric tests of anorectal function in healthy adults

OBJECTIVE: Although tests of anorectal function are useful in the assessment of defecation disorders, there is inadequate and inconsistent information regarding normative data. Also, there are discrepancies in manometric techniques and data interpretation. Our aim was to perform a comprehensive evaluation of anorectal function in healthy adults. METHODS: We used a 6-mm diameter probe containing six radially arrayed microtransducers, and a 4-cm-long latex balloon for performing anorectal manometry in 45 healthy subjects who were controlled for gender and age. Sequentially, subjects were asked to squeeze, bear down, or blow up a party balloon. Subsequently, rectal sensation, rectal compliance, and rectoanal reflexes were assessed simultaneously by performing intermittent phasic balloon distentions. Additionally, balloon defecation, pudendal nerve latency, and saline continence tests were performed. RESULTS: In men, the anal sphincter was longer (p < 0.05) and squeeze sphincter pressure and squeeze duration were higher (p < 0.01), but resting sphincter pressure was similar to that in women. When bearing down, although not significant, the defecation index was higher in men. Distinct thresholds for rectal sensation were identified but there was no gender difference. Likewise, rectal compliance and balloon expulsion time were similar. However, during saline infusion, the onset of first leak and total volume retained were higher (p < 0.001) and pudendal nerve latency was shorter (p < 0.05) in men. Overall, parity or age did not influence anorectal function. CONCLUSIONS: This study represents the most comprehensive age- and gender-controlled assessment of anorectal function using solid state technology. Gender influences some parameters of anorectal function. Our results could serve as a valuable resource of normative data.     

Functional disorders of defecation: Evaluation and treatment

Opinion statement Functional disorders of defecation are common and often overlap with slow-transit constipation. They are comprised of functional obstructive conditions such as dyssynergic defecation, as well as structural obstructive conditions such as rectal prolapse, excessive perineal descent, and rectocele. Evaluation includes detailed history and rectal and pelvic exam together with physiologic tests such as anorectal manometry, balloon expulsion test, defecography, and MRI. Treatment involves several medical, behavioral, and surgical approaches. Recently, randomized controlled trials have shown that biofeedback therapy is an effective treatment for dyssynergic defecation. Stapled transanal rectal resection appears to be a promising technique for treating defecation disorders associated with rectocele, excessive perineal descent, and mucosal intussusception, but controlled trials are lacking.     

Phenotypic variation in functional disorders of defecation

BACKGROUND & AIMS: Although obstructed defecation is generally attributed to pelvic floor dyssynergia, clinical observations suggest a wider spectrum of anorectal disturbances. Our aim was to characterize phenotypic variability in constipated patients by anorectal assessments. METHODS: Anal pressures, rectal balloon expulsion, rectal sensation, and pelvic floor structure (by endoanal magnetic resonance imaging) and motion (by dynamic magnetic resonance imaging) were assessed in 52 constipated women and 41 age-matched asymptomatic women. Phenotypes were characterized in patients by principal components analysis of these measurements. RESULTS: Among patients, 16 had a hypertensive anal sphincter, 41 had an abnormal rectal balloon expulsion test, and 20 had abnormal rectal sensation. Forty-nine patients (94%) had abnormal pelvic floor motion during evacuation and/or squeeze. After correcting for age and body mass index, 3 principal components explained 71% of variance between patients. These factors were weighted most strongly by perineal descent during evacuation (factor 1), anorectal location at rest (factor 2), and anal resting pressure (factor 3). Factors 1 and 3 discriminated between controls and patients. Compared with patients with normal (n = 23) or reduced (n = 18) perineal descent, patients with increased (n = 11) descent were more likely (P < or = .01) to be obese, have an anal resting pressure >90 mm Hg, and have a normal rectal balloon expulsion test result. CONCLUSIONS: These observations demonstrate that functional defecation disorders comprise a heterogeneous entity that can be subcharacterized by perineal descent during defecation, perineal location at rest, and anal resting pressure. Further studies are needed to ascertain if the phenotypes reflect differences in the natural history of these disorders.     

Discriminative Value of Anorectal Manometry in Clinical Practice

Guidelines recommend anorectal manometry in patients with fecal incontinence and chronic constipation. However, limited evidence supports the utility of manometric testing. We retrospectively reviewed tracings obtained between November 2005 and May 2008. A total of 298 patients (86% women; average age 52 years) were included. The main indications were incontinence (51%) and constipation (42%). Patients suffering from incontinence were older and had lower resting and squeeze pressure compared to continent patients. However, the discriminative power of manometric pressure data was poor, with low sensitivity and specificity. An abnormal straining pattern suggesting dyssynergic defecation was seen in 43% of constipated patients compared to 13% of patients with fecal incontinence. A concordance between manometric patterns and the balloon expulsion test was seen in 72%. The low sensitivity and specificity of manometric parameters does not support the routine use of anorectal manometry in patients with defecation disorders.     

Comparing the efficacy of biofeedback and balloon-assisted training in the treatment of dyssynergic defecation

BACKGROUND:

Dyssynergic defecation does not respond appropriately to routine treatments for constipation. Recently, research has shown that biofeedback therapy is useful in anorectal dyssynergia.

OBJECTIVE:

To compare two treatment modalities for patients experiencing dyssynergic defecation.

METHODS:

Sixty-five subjects with dyssynergic defecation were recruited and randomly allocated to one of two treatment groups: balloon defecation training and biofeedback therapy. In the first group, a balloon was inserted into the rectum and inflated by water injection so that the patient experienced the sensation of a full rectum and, thus, the need to defecate. The patient was subsequently asked to reject the balloon. In the biofeedback group, the pen electrode of an electromyographic biofeedback device was inserted into the rectum, with the patient subsequently being asked to increase abdominal pressure and relax the rectal muscles accordingly.

RESULTS:

The findings showed a reduction in constipation in both groups. The ability to reject the balloon (volume and time) was significantly better in postintervention measurements; however, better results were found in the biofeedback arm of the study. Patient satisfaction after treatment reached 52% with balloon training and 79% in the biofeedback group. Reports of incomplete evacuation and the need for digit use during defecation remained constant after treatment in balloon-trained patients.

CONCLUSION:

Biofeedback training appeared to be superior to balloon defecation training and resulted in measurable changes in subjective and objective variables of dyssynergia.     

Effectiveness of Biofeedback Therapy on Quality of Life in Patients with Dyssynergic Defecation Disorder

Background: The first option to be considered in the treatment of functional defecation disorder is to correct the dyssynergia. However, limited studies exist to show the effectiveness of biofeedback.Objective: We evaluated the effect of biofeedback on the severity of constipation, quality of life, and anorectal manometry in patients with dyssynergic defecation in which the biofeedback method was applied.Methods: Effectiveness of biofeedback method on the quality of life of 24 dyssynergic defecation patients according to Rome III criteria after clinical and balloon expulsion tests (BETs) and colonic transit time was measured. Data were collected with patient identification form, Bristol Stool Chart, Constipation Quality of Life Scale forms, Visual Analogue Scale, diaphragmatic breathing exercises form, constipation diary, and constipation biofeedback monitoring form. Dyssnergic defecation cases received 6-week biofeedback training. For the same timeframe, the control group had a catheter into the rectum without any intervention.Results: Constipation severity was reduced in both groups before biofeedback to post-biofeedback (P < .05). Anal canal pressure, BET, colonic transit time, and quality of life significantly improved in biofeedback patients compared with controls.Conclusions: Biofeedback has a favorable effect on therapy and quality of life in dyssynergic defecation cases.     

Biofeedback benefits only patients with outlet dysfunction, not patients with isolated slow transit constipation

BACKGROUND & AIMS: Biofeedback is reported to be as effective for slow transit constipation as for pelvic floor dyssynergia and no more effective than education. We aimed to test the hypothesis that biofeedback benefits only patients with pelvic floor dyssynergia, describe the physiologic mechanism of treatment, and identify predictors of success. METHODS: Fifty-two patients (49 women; average age, 35 years), all with delayed whole gut transit, included 34 with pelvic floor dyssynergia, 12 with slow transit only, and 6 who met only 1 of 2 criteria for pelvic floor dyssynergia. All received 5 weekly biofeedback sessions directed at increasing rectal pressure and relaxing pelvic floor muscles during straining plus practice defecating a balloon. Patients were retested by questionnaire; symptom diary; balloon defecation; transit study at 1, 6, 12, and 24 months; and anorectal manometry at 1 and 6 months. RESULTS: At 6 months, greater improvements were seen in pelvic floor dyssynergia compared with slow transit only; 71% versus 8% reported satisfaction ( P = .001), and 76% versus 8% reported >/=3 bowel movements per week ( P < .001). Improvements were maintained at 24 months of follow-up. Biofeedback eliminated dyssynergia in 91% and enabled 85% to defecate the balloon. Satisfaction was correlated with improved ability to defecate the balloon (rho = .73; P < .001), reductions in dyssynergia (rho = .69; P < .001), and increased rectal pressure during straining (rho = .36; P < .01). Success was predicted by pelvic floor dyssynergia, milder constipation, and less frequent abdominal pain at baseline. CONCLUSIONS: Biofeedback is an effective treatment for pelvic floor dyssynergia but not slow transit constipation.     

Difficult defecation: difficult problem assessment and management; what really helps?

Difficult defecation is a common and perhaps underrecognized cause of chronic constipation. While the history and a careful digital rectal examination are very useful for diagnosing defecatory disorders, the diagnosis needs to be confirmed by anorectal tests. Anorectal manometry and a rectal balloon expulsion test generally suffice to diagnose defecatory disorders; barium or MR defecography may necessary in selected cases. Colonic transit is normal or slow in patients with defecatory disorders. Pelvic floor retraining by biofeedback therapy is superior to laxatives for managing defecatory disorders.     

慢性特发性便秘患者肛门直肠测压表现及西沙必利的疗效研究

目的研究慢性特发性便秘（CIC）患者肛门直肠动力及直肠对容量刺激感觉的变化，同时观察西沙必利对CIC的疗效及对上述指标的影响。方法用肛门直肠测压法检测30例CIC患者，服用西沙必利前后的直肠动力及直肠对容量刺激感觉的变化。20名健康者作对照。结果肛门直肠括约肌最大收缩压降低（P＜0．05），引起直肠肛门抑制性反射的最小松弛容量（MRV）增大（P＜0．05），直肠内部容量刺激的排便阈值及疼痛阈值均明显增加（P＜0．01）；西沙必利10mg每日3次治疗4周可显著改善CIC患者上述异常改变（P＜0．01），增加CIC患者排便次数（P＜0．01），治疗总有效率为46，67％。结论CIC患者存在肛门直肠动力及内脏感觉异常，西沙必利可改善上述异常表现，对约半数CIC患者具有良好疗效。     

直肠前膨出与功能性排便障碍：肛门直肠压力与感觉功能检测

背景：直肠前膨出（RC）是一种多见于女性的肛肠疾病,与功能性排便障碍（FDD）的关系目前尚不明。目的：研究伴RC的FDD患者肛门直肠压力和感觉功能的变化,探讨RC与FDD的关系。方法：选取28例伴RC的FDD患者并分为伴轻度RC的FDD组和伴中-重度RC的FDD组,设不伴RC的FDD患者作为对照。所有患者行球囊排出试验、肛门直肠压力和感觉功能检测,并按照罗马Ⅲ标准将FDD患者进一步分为排便协同失调（F3a）和排便推进不足（F3b）两种亚型。结果：除伴中-重度RC的FDD组直肠排便收缩压显著低于不伴RC的FDD组外（P〈0.05）,其余各组间直肠静息压、肛管静息压、肛管最大缩榨压、直肠排便收缩压、肛门括约肌松弛率以及初始感觉容量、产生便意容量和最大耐受容量均无明显差异。与不伴RC的FDD组相比,伴RC的FDD组中F3b亚型比例显著升高（P〈0.05）。结论：伴中-重度RC的FDD患者直肠排便收缩压明显降低,伴RC的FDD患者多表现为F3b亚型,提示RC与FDD的发病可能具有相关性。     

Defecation disorders. Characteristics of manometric studies and rehabilitation

The authors review the literature and their personal experience about the systematic exploration of defecation disorders by anorectal manometry and colpocystodefecography. They stress the importance of combining functional and morphological evaluation, in order to avoid inappropriate surgery. Concerning anorectal manometry, the determination of the smallest volume of rectal distention inducing a complete relaxation of the internal anal sphincter was found more useful than the maximal tolerable volume in the exploration of defecation disorders. Finally, the authors report the results of biofeedback conditioning prescribed in 30 patients (27 women, 3 men, mean age: 55 years) with defecation disorders (terminal constipation in 21, fecal incontinence in 9 patients). Several characteristics of anorectal manometry and of defecography were significantly improved after biofeedback conditioning.     

慢性功能性便秘肛直肠压力检测及EMG生物反馈训练疗效的研究

目的探讨慢性功能性便秘(CFC)患者肛直肠压力及肌电(EMG)活动特点,同时观察生物反馈训练系统对CFC患者的疗效及对上述指标的影响.方法用BIOLAB动力学参数监测系统(液态式),多道胃肠功能检查仪对144例CFC患者检测,并用OrionPC/12mEMG生物反馈治疗仪进行肌电评估和训练,20例健康者作对照.结果与健康对照组相比,CFC患者肛管静息压稍下降(P＞0.01)、最大缩榨压明显降低(P＜0.01),直肠感知阈和最大耐受量均显著增高(P＜0.01);EMG评估CFC患者盆底肌与腹前斜肌有矛盾运动100%,其运动幅值盆底肌静息状态下升高(P＜0.01)和腹前斜肌降低(P＜0.01);OrionPC/12mEMG生物反馈训练治疗后可显著改善CF C患者上述异常改变(P＜0.01),生物反馈治疗CFC患者临床症状改善,总有效率为84.03%,增加疗程的频次、缩短治疗间隔以及辅助家庭训练等可以提高疗效和降低复发率(P＜0.01).结论CFC患者存在肛门直肠动力、感知觉及肌电活动异常,OrionPC/12mEMG生物反馈系统可以改善上述异常表现,对84.03%的CFC患者具有良好的疗效,较长时间的强化训练可望提高近期疗效,辅助家庭训练可降低复发率.     

Customized biofeedback therapy improves results in fecal incontinence

Background and aims Biofeedback therapy has been extensively used and accepted in fecal incontinence, but reports of its efficiency vary. We evaluated feedback therapy efficiency when (a) selecting the patients subject of the therapy, and (b) customizing the therapy protocol used for each patient.Patients and methods Fifty-three patients with fecal incontinence were selected for biofeedback training. The treatment program was customized for each patient depending on the underlying dysfunction, the patients cooperative and learning attitude, and the patients progress. Biofeedback efficiency was measured using clinical scores, subjective satisfaction of the patient, and manometry.Results Incontinent scores showed improvement in 66% of patients and good improvement in 11% and 15%, respectively, indicating an overall excellent effect of the therapy. Subjective satisfaction was strongly correlated with the previous incontinent scores. Comparison of manometry parameters before and after biofeedback therapy, including maximum anal resting, maximum anal squeeze pressure, and maximum duration of the squeeze, all showed significant differences. In addition, the sensory threshold significantly decreased after biofeedback therapy. Clinical improvements were maintained during the following 12 months.Conclusion Biofeedback improves objective and subjective parameters of anorectal function. Selection of patients and customization of the therapy program increased biofeedback efficiency for the treatment of fecal incontinence.     

Effect of Biofeedback Therapy in Constipation According to Rectal Sensation

Background/Aims

The pathophysiologic mechanism of rectal hyposensitivity (RH) is not well documented, and the significance of RH in biofeedback therapy (BFT) has not been evaluated. Thus, we aimed to assess the effect of BFT in constipated patients according to the presence of RH.

Methods

Five hundred and ninety constipated patients (238 males and 352 females) underwent anorectal physiologic assessments. Of these, anorectal manometry was performed before and after BFT in 244 patients (63 RH and 181 non-RH patients).

Results

The success rate of BFT was 56% in the RH and 61% in the non-RH group (p=0.604). The measurements of resting pressure, squeezing pressure, desire to defecate volume, urge to defecate volume, and maximum volume were decreased after BFT in the RH group (p<0.05), whereas only resting and squeezing pressures were decreased in the non-RH group (p<0.05). Among the RH group, individuals who responded to BFT showed decreased resting pressure, squeezing pressure, desire to defecate, urge to defecate, and maximum volume and increased balloon expulsion rate; among those who did not respond to BFT, only desire to defecate volume was improved.

Conclusions

In constipated patients with RH, changes of anorectal manometric findings differed in comparison to patients without RH. The responses to BFT showed both anorectal muscle relaxation and restoration of rectal sensation.     

Functional activity of the rectum： A conduit organ or a storage organ or both？

AIM: To investigate whether the degree of rectal distension could define the rectum functions as a conduit or reservoir. METHODS: Response of the rectal and anal pressure to 2 types of rectal balloon distension, rapid voluminous and slow gradual distention, was recorded in 21 healthy volunteers (12 men, 9 women, age 41.7±10.6 years). The test was repeated with sphincteric squeeze on urgent sensation. RESULTS: Rapid voluminous rectal distension resulted in a significant rectal pressure increase (P < 0.001), an anal pressure decline (P < 0.05) and balloon expulsion. The subjects felt urgent sensation but did not feel the 1st rectal sensation. On urgent sensation, anal squeeze caused a significant rectal pressure decrease (P < 0.001) and urgency disappearance. Slow incremental rectal filling drew a rectometrogram with a "tone" limb representing a gradual rectal pressure increase during rectal filling, and an "evacuation limb" representing a sharp pressure increase during balloon expulsion. The curve recorded both the 1st rectal sensation and the urgent sensation. CONCLUSION: The rectum has apparently two functions: transportation (conduit) and storage, both depending on the degree of rectal filling. If the fecal material received by the rectum is small, it is stored in the rectum until a big volume is reached that can affect a degree of rectal distension sufficient to initiate the defecation reflex. Large volume rectal distension evokes directly the rectoanal inhibitory reflex with a resulting defecation.