Understanding the physiology of human defaecation and disorders of continence and evacuation.

The act of defaecation, although a ubiquitous human experience, requires the coordinated actions of the anorectum and colon, pelvic floor musculature, and the enteric, peripheral and central nervous systems. Defaecation is best appreciated through the description of four phases, which are, temporally and physiologically, reasonably discrete. However, given the complexity of this process, it is unsurprising that disorders of defaecation are both common and problematic; almost everyone will experience constipation at some time in their life and many will develop faecal incontinence.

Anterior resection syndrome.

Up to 80% of patients with rectal cancer undergo sphincter-preserving surgery. It is widely accepted that up to 90% of such patients will subsequently have a change in bowel habit, ranging from increased bowel frequency to faecal incontinence or evacuatory dysfunction. This wide spectrum of symptoms after resection and reconstruction of the rectum has been termed anterior resection syndrome.

Prospective randomized double-blind study of temporary sacral nerve stimulation in patients with rectal evacuatory dysfunction and rectal hyposensitivity.

Objective: Prospective randomized double-blind placebo-controlled crossover trial of 14 female patients (median age 52 [30-69] years) with proctographically defined evacuatory dysfunction (ED) and demonstrable rectal hyposensitivity (elevated thresholds to balloon distension in comparison with age- and sex-matched controls).

Background: Sacral nerve stimulation (SNS) is an evolving treatment for constipation. However, variable outcomes might be improved by better patient selection.

The physiology of human defecation.

Human defecation involves integrated and coordinated sensorimotor functions, orchestrated by central, spinal, peripheral (somatic and visceral), and enteric neural activities, acting on a morphologically intact gastrointestinal tract (including the final common path, the pelvic floor, and anal sphincters). The multiple factors that ultimately result in defecation are best appreciated by describing four temporally and physiologically fairly distinct phases. This article details our current understanding of normal defecation, including recent advances, but importantly identifies those areas where knowledge or consensus is still lacking.

Fecal incontinence in men: coexistent constipation and impact of rectal hyposensitivity.

Background: The pathophysiology of fecal incontinence in men is poorly established.

Objective: The aim of this study was to assess the coexistence of constipation and determine the impact of rectal sensorimotor dysfunction in males with fecal incontinence.

Setting: This study was conducted at a tertiary referral center.

Accurate localization of a fall in pH within the ileocecal region: validation using a dual-scintigraphic technique.

Stereotypical changes in pH occur along the gastrointestinal (GI) tract. Classically, there is an abrupt increase in pH on exit from the stomach, followed later by a sharp fall in pH, attributed to passage through the ileocecal region. However, the precise location of this latter pH change has never been conclusively substantiated.

Efficacy of sacral nerve stimulation for fecal incontinence in patients with anal sphincter defects.

Purpose: Sacral nerve stimulation has traditionally been used to treat patients with fecal incontinence with intact anal sphincters. This rationale has been challenged, but it remains unknown if its efficacy is related to the extent of the sphincter injury.

Methods: This was a prospective study of 15 patients with sphincter defects (9 combined, 2 external only, and 4 internal only) undergoing sacral nerve stimulation for fecal incontinence.

Simple cutaneous advancement flap anoplasty for resistant chronic anal fissure: a prospective study.

Background: A proportion of patients with chronic anal fissure have persistent symptoms and pathology despite optimum conservative therapies. Lateral anal sphincterotomy, the standard surgical treatment, is associated with functional compromise in a minority of patients. Sphincter-sparing anoplasty has been advocated as an alternative procedure for those with "low pressure" sphincters.

Rectal augmentation: short- and mid-term evaluation of a novel procedure for severe fecal urgency with associated incontinence.

Background: Rectal augmentation (RA) with or without electrically stimulated gracilis neosphincter (ESGN) was developed to address the physiologic and anatomic abnormalities present in a subset of patients with incapacitating fecal urgency and associated urge fecal incontinence (UFI). This study evaluated the short- and medium-term clinical and physiologic results.

Methods: Eleven patients with fecal urgency and UFI underwent RA, 6 with concomitant ESGN formation.

In patients with slow transit constipation, the pattern of colonic transit delay does not differentiate between those with and without impaired rectal evacuation.

Background: Severe constipation may be subclassified on the basis of speed of colonic transit and efficacy of rectal evacuation. It is hypothesized that rectal evacuatory disorder (RED) may be associated with a secondary transit delay.

Objectives: To determine whether scintigraphy can discriminate between slow transit constipation (STC) with or without coexistent RED on the basis of progression of isotope throughout the colon and by analyses of specific regions of interest.

Unilateral pudendal neuropathy is common in patients with fecal incontinence.

Purpose: Pudendal neuropathy and fecal incontinence frequently coexist; however, the contribution of neuropathy is unknown. The pudendal nerve innervates the external anal sphincter muscle, anal canal skin, and coordinates reflex pathways. Lateral dominance or a dominantly innervating nerve and its subsequent damage may have major implications in the etiology and treatment of fecal incontinence.

A novel technique to identify patients with megarectum.

Purpose: Traditional methods of identifying patients with persistent dilation of the rectum, or megarectum, are associated with inherent methodologic limitations. The purpose of this study was to use a barostat to establish criteria for the diagnosis of megarectum and to assess rectal diameter during isobaric (barostat) and volumetric (barium contrast) distention protocols in constipated patients with megarectum on anorectal manometry.

Methods: During fluoroscopic screening, rectal diameter was measured at minimum distending pressure of the rectum, achieved using a barostat.

Multimedia article. External pelvic rectal suspension (the express procedure) for internal rectal prolapse, with or without concomitant rectocele repair: a video demonstration.

Purpose: Internal rectal prolapse has been proposed as a cause of symptomatic rectal evacuatory dysfunction. Abdominal rectopexy, the standard surgical approach, has significant attendant risk and does not address any concomitant rectocele. This video was designed to demonstrate a novel surgical method that uses porcine collagen implants (Permacol), designed to correct internal rectal prolapse, with or without rectocele.

Rectal hyposensitivity.

Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension that is diagnosed during anorectal physiologic investigation. There have been few direct studies of this physiologic abnormality, and its contribution to the development of functional bowel disorders has been relatively neglected. However, it appears to be common in patients with such disorders, being most prevalent in patients with functional constipation with or without fecal incontinence.

Rectal intussusception: a study of rectal biomechanics and visceroperception.

Objectives: Rectal intussusception (RI) is a significant cause of morbidity amongst those with a rectal evacuatory disorder. The pathophysiology is unknown, but may involve abnormal biomechanics of the rectal wall similar to that previously demonstrated in patients with overt rectal prolapse (RP). Using an electromechanical barostat, this study aimed to investigate the biomechanics and visceroperception of the rectal wall in patients with RI.

Systematic review of surgical options for idiopathic megarectum and megacolon.

Objective: A subgroup of patients with intractable constipation has persistent dilatation of the bowel, which in the absence of an organic cause is termed idiopathic megabowel (IMB). The aim of this systematic review was to evaluate the published outcome data of surgical procedures for IMB in adults.

Methods: Electronic searches of the MEDLINE (PubMed) database, Cochrane Library, EMBase, and Science Citation Index were performed.

Rectal intussusception: characterization of symptomatology.

Purpose: Rectal intussusception is a common finding at evacuation proctography; however, its significance has been debated. This study was designed to characterize clinically and physiologically a large group of patients with rectal intussusception and test the hypothesis that certain symptoms are predictive of this finding on evacuation proctography.

Methods: A total of 896 patients underwent evacuation proctography from which three groups were identified: those with isolated rectal intussusception (n = 125), those with isolated rectocele (n = 100), and those with both abnormalities (n = 152).

Rectal hypersensitivity worsens stool frequency, urgency, and lifestyle in patients with urge fecal incontinence.

Purpose: Rectal sensory mechanisms are important in the maintenance of fecal continence. Approximately 50 percent of patients with urge incontinence have lowered rectal sensory threshold volumes (rectal hypersensitivity) on balloon distention. Rectal hypersensitivity may underlie the heightened perception of rectal filling; however, its impact on fecal urgency and incontinence is unknown.

Rectal hyposensitivity: a disorder of the rectal wall or the afferent pathway? An assessment using the barostat.

Objectives: Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension. Diagnosis on the basis of abnormal threshold volumes on balloon distension alone may be inaccurate due to the influence of differing rectal wall properties. The aim of this study was to investigate whether RH was actually due to impaired afferent nerve function or whether it could be secondary to abnormalities of the rectal wall.

Anal sphincter morphology in patients with full-thickness rectal prolapse.

Purpose: The aim of this study was to assess the morphologic change of the anal canal in patients with rectal prolapse.

Methods: The endoanal ultrasound scans of 18 patients with rectal prolapse were compared with those of 23 asymptomatic controls. The thickness and area of the internal anal sphincter and submucosa were measured at three levels.

Risk factors in acquired faecal incontinence.

Acquired faecal incontinence arising in the non-elderly population is a common and often devastating condition. We conducted a retrospective cohort analysis in 629 patients (475 female) referred to a tertiary centre, to determine the relative importance of individual risk factors in the development of faecal incontinence, as demonstrated by abnormal results on physiological testing. Potential risk factors were identified in all but 6% of patients (7 female, 32 male).