Idiopathic megarectum in adults. An assessment of manometric and radiologic variables

Constipated patients with functional defecatory disorder have secondary rectal hyposensitivity due to altered rectal biomechanics

BACKGROUND AND AIM

Rectal hyposensitivity (RH) is common in constipation and often coexists with functional defecatory disorder (FDD). Rectal sensory thresholds are routinely evaluated with the anorectal manometry probe; however, the gold standard for the assessment of rectal sensitivity is with a barostat, use of which is limited by time constraints and availability. A novel rapid barostat bag (RBB) may facilitate measurements of rectal sensitivity. The aim is to evaluate the relationship between RH (measured by the RBB) and FDD (defined as any minor disorder of rectoanal coordination by the London classification) in constipated patients.

METHODS

Consecutive constipated patients referred for anorectal function testing underwent anorectal manometry with the 3D-HDAM probe as well as rectal sensation testing with the RBB pump. RH was defined by volume to first sensation >30%, urge to defecate >80%, or discomfort >100% (normalized to rectal capacity).

RESULTS

Fifty-three percent of constipated patients had RH. Patients with FDD had a significantly increased volume to first sensation (134.5 mL vs 102.0, P = 0.02), urge to defecate (187.0 mL vs 149.0, P = 0.04), and rectal capacity (253.5 mL vs 209.0, P = 0.04) compared to constipated patients without FDD. There was no difference in normalized sensory thresholds (percent of rectal capacity) nor the prevalence of hyposensitivity to each sensory threshold nor overall hyposensitivity.

CONCLUSION

Patients with FDD, when measured with the RBB, have increased sensory thresholds on volumetric distension, but RH was not observed when sensory threshold volume were normalized to rectal capacity. This may reflect "secondary" RH due to altered rectal biomechanics.

Unusual case of cholecystocolonic fistula secondary to megabowel

Cholecystocolonic fistula with associated idiopathic megabowel (megacolon and megarectum) is a rare presentation as acute large bowel obstruction. Frequently presenting with chronic constipation, acute bowel obstruction is rarely encountered in the presence of concomitant cholecystocolonic fistula. This presents diagnostic and management difficulties with no consensus on appropriate surgical approach. This case highlights the outcomes following emergency total colectomy and subtotal cholecystectomy as a single-stage procedure for a 68-year-old man presenting with cholecystocolonic fistula secondary to idiopathic megabowel as acute large bowel obstruction.

Rectal sensorimotor dysfunction in constipation

The pathophysiological mechanisms underlying chronic constipation in both adults and children remain to be unravelled. This is a not inconsiderable challenge, but is fundamental to improving management of such patients. Rectal sensorimotor function, which encompasses both sensation and motility, as well as biomechanical components (compliance, capacity), is now strongly implicated in the pathogenesis of constipation. Rectal hyposensitivity, rectal hypercompliance, increased rectal capacity, rectal motor dysfunction (phasic contractility and tone), and altered rectoanal reflex activity are all found in constipated patients, particularly in association with 'functional' disorders of defaecation (i.e. pelvic floor dyssynergia). This review covers contemporary understanding of how components of rectal sensorimotor function may contribute to symptom development in both adult and paediatric populations. The complex interaction between sensory/motor/biomechanical domains, and how best to measure these functions are addressed, and where data exist, the impact of sensorimotor dysfunction on therapeutic outcomes is highlighted.

Rectal hyposensitivity: pathophysiological mechanisms

Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension. It may occur due to afferent nerve dysfunction and/or secondary to abnormal structural or biomechanical properties of the rectum. The aim of this study was to determine the contribution of these underlying pathophysiological mechanisms by systematically evaluating rectal diameter, compliance and afferent nerve sensitivity in patients with RH, using methodology employed in clinical practice. The study population comprised 45 (33 women; median age 48, range 25-72 years) constipated patients (Rome II criteria) with RH and 20 with normal rectal sensitivity on balloon distension and 20 healthy volunteers. Rectal diameter was measured at minimum distending pressure during isobaric distension under fluoroscopic screening. Rectal compliance was assessed during phasic isobaric distension by measuring the slope of the pressure-volume curve. Electrical stimulation of the rectal mucosa was employed to determine afferent nerve function. Values were compared to normal ranges established in healthy volunteers. The upper limits of normal for rectal diameter, compliance and electrosensitivity were 6.3 cm, 17.9 mL mmHg(-1) and 21.3 mA respectively. Among patients with RH, rectal diameter, but not compliance, was increased above the normal range (megarectum) in seven patients (16%), two of whom had elevated electrosensitivity thresholds. Rectal diameter and compliance were elevated in 23 patients (51%), nine of whom had elevated electrosensitivity thresholds. The remaining 15 patients (33%) with RH had normal rectal compliance and diameter, all of whom had elevated electrosensitivity thresholds. Two-third of the patients with RH on simple balloon distension have elevated rectal compliance and/or diameter, suggesting that impaired perception of rectal distension is due to inadequate stimulation of the rectal afferent pathway. However, a proportion of such patients also appear to have impaired nerve function. In the remaining one-third of the patients, rectal diameter and compliance are normal, while electrosensitivity thresholds are elevated, suggestive of true impaired afferent nerve function. Identification of these subgroups of patients with RH may have implications regarding their management.

Novel concepts in the diagnosis, pathophysiology and management of idiopathic megabowel

A proportion of patients with intractable constipation have persistent dilatation of the bowel, which in the absence of an organic cause is termed idiopathic megabowel (IMB). Whilst uncommon, this condition results in considerable morbidity. Traditional methods of identifying such patients are associated with inherent methodological limitations with anorectal manometry and contrast studies overestimating and underestimating the prevalence of the condition, respectively. Recently, controlled, pressure-based distension during fluoroscopic imaging has allowed more accurate identification of patients on the basis of a rectal diameter > 6.3 cm at the minimum distension pressure. Histopathological abnormalities of all three final effectors of sensorimotor function have been reported, although it remains unclear whether these changes are primary, secondary or epiphenomic. Physiological abnormalities of sensorimotor function, namely impaired perception of rectal distension and delayed colonic transit are well documented in patients with IMB. Further, the recent demonstration of two subgroups of patients, defined on the basis of rectal compliance, suggests the possibility that they differ pathophysiologically, although the clinical relevance of this distinction is uncertain. Surgery is performed when conservative therapy is ineffective or poorly tolerated. Numerous procedures have been attempted with variable success rates and significant mortality and morbidity. Surgery should preferably be performed in specialist centres given the relative infrequency with which such patients are encountered, and that they require comprehensive clinical, psychological and physiological evaluation preoperatively.

Audit of constipation in a gastroenterology referral center

This study was designed to assess the various subtypes of functional constipation in a referral gastrointestinal center of a Latino-American country. All patients referred for evaluation of constipation during a 10-year period were audited, and those with functional constipation according to Rome I criteria classified by physiologic tests of colonic transit, as well as tests of anorectal and pelvic floor function. More than 70% of patients with functional constipation had evidence of pelvic floor dysfunction, whereas those with slow transit and constipation-predominant irritable bowel syndrome subtypes were less frequently represented. Even in a setting different from those most frequently reported in the literature, pelvic floor dysfunction represents the most common cause of functional constipation. Simple, physiologic testing is needed and useful for the diagnosis. This fact has therapeutic implications, especially because many such patients may benefit from biofeedback.

Manometric assessment of idiopathic megarectum in constipated children

AIM: Chronic constipation is a frequent finding in children. In this age range, the concomitant occurrence of megarectum is not uncommon. However, the definition of megarectum is variable, and a few data exist for Italy. We studied anorectal manometric variables and sensation in a group of constipated children with megarectum defined by radiologic criteria. Data from this group were compared with those obtained in a similar group of children with recurrent abdominal pain.

METHODS: Anorectal testing was carried out in both groups by standard manometric technique and rectal balloon expulsion test.

RESULTS: Megarectum patients displayed discrete abnormalities of anorectal variables and sensation with respect to controls. In particular, the pelvic floor function appeared to be impaired in most patients.

CONCLUSION: Constipated children with megarectum have abnormal anorectal function and sensation. These findings may be helpful for a better understanding of the pathophysiological basis of this condition.

Classical conditioned response of rectosigmoid motility and regional cerebral activity in humans

The relationship between the central processes of classical conditioning and conditioned responses of the gastrointestinal function is incompletely understood in humans. We tested the hypothesis that the rectosigmoid motility becomes conditioned with anticipatory painful somatosensory stimulus and that characteristic brain areas become activated during anticipation. In nine right-handed healthy male subjects, a loud buzzer (CS, conditional stimulus) was paired with painful transcutaneus electrical nerve stimulation to the right hand (unconditional stimulus). Rectosigmoid muscle tone measured by the barostat as the intrabag volume, phasic contractions of the bowel measured as the number of phasic volume events (PVEs), and regional cerebral blood flow assessed by positron emission tomography (PET), were measured before and after conditioning. Following conditional trials, the bag volume after CS alone did not show significant changes between before and after the stimulus, but the number of PVEs after 2-minute interval of the CS alone was significantly greater than that before the stimulus (P < 0.05). The PET data showed the conditioning elicited significant cerebral activation of the prefrontal, anterior cingulate, parietal and insula cortices (P < or = 0.001, uncorrected). Rectosigmoid motility can be conditioned with increase in phasic contractions in humans.

Magnetic resonance imaging of the rectum during distension

PURPOSE

A knowledge of the relationships between the rectum and its surrounding structures during distention may improve our understanding of the results of studies assessing rectal sensory-motor responses to distention. This magnetic resonance imaging study was designed to assess the shape of the rectum and the degree of distention at which the surrounding structures are compressed.

METHODS

Nine healthy patients underwent magnetic resonance imaging of the rectum under resting conditions and after the inflation of a plastic bag to volumes of 50, 100, 150, 200, and 250 ml. The thickness of the rectovesical space was assessed as a measure of the compression of the perirectal structures, and the perception of sensations were recorded.

RESULTS

The shape of the rectum changed from being quasicylindrical at distention volumes of <100 ml to bean-shaped at larger volumes. The thickness of the rectovesical space at a distention volume of 50 ml was the same as when the bag was not inflated, but it progressively decreased until the difference became statistically significant at distention volumes of > or = 200 ml, corresponding to a mean +/- standard deviation rectal radius of 2.66 +/- 0.37 cm. Statistically significant compression of the rectovesical space was recorded when the sensations of gas, desire to defecate, and urgency were perceived.

CONCLUSIONS

The shape of the rectum changes during distention; it significantly compresses the extrarectal structures in the tested range of distention that induces non-painful sensations. Magnetic resonance imaging is a useful means of assessing the morphologic changes in the rectum during distention.

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. Only peer-reviewed articles of surgery for IMB published in the English language were evaluated. Studies of all surgical procedures were included, providing they were performed on 3 or more patients, and overall success rates were documented. Studies were critically appraised in terms of design and methodology, inclusion criteria, success, mortality and morbidity rates, and functional outcomes.

RESULTS

A total of 27 suitable studies were identified, all evidence was low quality obtained from case series, and there were no comparative studies. The studies involved small numbers of patients (median 12, range 3-50), without long-term follow-up (median 3 years, range 0.5-7). Inclusion of subjects, methods of data acquisition, and reporting of outcomes were extremely variable. Subtotal colectomy was successful in 71.1% (0%-100%) but was associated with significant morbidity related to bowel obstruction (14.5%, range 0%-29%). Segmental resection was successful in 48.4% (12.5%-100%), and recurrent symptoms were common (23.8%). Rectal procedures achieved a successful outcome in 71% to 87% of patients. Proctectomy, the Duhamel, and pull-through procedures were associated with significant mortality (3%-25%) and morbidity (6%-29%). Vertical reduction rectoplasty (VRR) offered promising short-term success (83%). Pelvic-floor procedures were associated with poor outcomes. A stoma provided a safe alternative but was only effective in 65% of cases.

CONCLUSIONS

Outcome data of surgery for IMB must be interpreted with extreme caution due to limitations of included studies. Recommendations based on firm evidence cannot be given, although colectomy appears to be the optimum procedure in patients with a nondilated rectum, restorative proctocolectomy the most suitable in those with dilatation of the colon and rectum, and VRR in those patients with dilatation confined to the rectum. Appropriately designed studies are required to make valid comparisons of the different procedures available.

Sensory retraining is key to biofeedback therapy for formed stool fecal incontinence

OBJECTIVES

Biofeedback is a nonsurgical treatment that reportedly produces good results in 65-75% of fecally incontinent patients. However, previous studies have not ruled out nonspecific treatment effects. It is also unknown whether biofeedback works primarily by improving the strength of the striated pelvic floor muscles or by improving the rectal perception. We aimed to 1) evaluate the efficacy of biofeedback in formed-stool fecal incontinence, 2) assess the relative contribution of sensory and strength retraining to biofeedback outcomes, and 3) identify patient characteristics that predict a good response to treatment.

METHODS

Twenty-four patients with frequent (at least once a week) solid-stool incontinence were provided with three to four biofeedback sessions. They were taught to squeeze in response to progressively weaker rectal distentions. Patients were re-evaluated by anorectal manometry and symptom diary 3 months after completing training and by diary and interview 6-12 months after training.

RESULTS

Seventeen (71%) were classified responders; 13 became continent and four reduced incontinence frequency by at least 75%. Clinical improvements were maintained at 12-month follow-up. At 3-month follow-up, responders had significantly lower thresholds for perception of rectal distention and for sphincter contraction, but squeeze pressures did not significantly differ from those of nonresponders. Baseline measures that predicted a favorable response were sensory threshold (50 ml or less), urge threshold (100 ml or less), lower threshold for sphincter contraction, and lower threshold for the rectoanal inhibitory reflex; neither anal squeeze pressure nor severity of incontinence predicted treatment outcome.

CONCLUSIONS

In solid-stool fecal incontinence biofeedback training effects are robust and seem not to be explained by expectancy or nonspecific treatment effect. Sensory retraining appears to be more relevant than strength training to the success of biofeedback.

Pathophysiology and management of bowel dysfunction in multiple sclerosis

The prevalence of bowel dysfunction in multiple sclerosis (MS) patients is higher than in the general population. Up to 70% of patients complain of constipation or faecal incontinence, which may also coexist. This overlap can relate to neurological disease affecting both the bowel and the pelvic floor muscles, or to treatments given. Bowel dysfunction is a source of considerable ongoing psychosocial disability in many patients with MS. Symptoms related to the bladder and the bowel are rated by patients as the third most important, limiting their ability to work, after spasticity and incoordination. Bowel management in patients with MS is currently empirical. Although general recommendations include maintaining a high fibre diet, high fluid intake, regular bowel routine, and the use of enemas or laxatives, the evidence to support the efficacy of these recommendations is scant. This review will examine the current state of knowledge regarding the pathophysiological mechanisms underlying bowel dysfunction in MS, outline the importance of proper clinical assessment of constipation and faecal incontinence during the diagnostic work-up, and propose various management possibilities. In the absence of clinical trial data on bowel management in MS, these should be considered as a consensus on clinical practice from a team specialized in bowel dysfunction.

Double-blind manometric assessment of two topical glyceryl trinitrate formulations in patients with chronic anal fissures

BACKGROUND

Chronic anal fissure is a frequent and troubling condition, that may need surgical sphincterotomy for relief of symptoms. However, this approach may yield minor incontinence in up to 30% of cases. Interest has, therefore, recently increased in "chemical sphincterotomy" by using topical glyceryl trinitrate ointment. Unfortunately, there is, to date, no specific pharmaceutical preparation of such compound.

AIMS

To compare, according to a randomized double-blind crossover study, the effects of a pharmaceutical preparation of a specific 0.2% glyceryl trinitrate ointment (PMF 303) and of the common preparation reported in the literature on the anal resting pressure in patients with anal fissure.

PATIENTS AND METHODS

Twelve patients with chronic anal fissure (6 males and 6 females, age range 23-60 years] were recruited for the study. Two paired manometric studies were carried out at one-week intervals. After the basal anal pressure had been assessed, the patients were randomized to receive either one of the two preparations, and manometric measurements were repeated at 20, 40 and 60 minutes.

RESULTS

No differences were found between anal resting pressure in the basal study. Both preparations were able to significantly decrease (p=0.001) anal pressure throughout the study period. No significant differences were found between the two preparations.

CONCLUSIONS

PMF 303 is able to decrease anal pressure in patients with anal fissure, to a similar extent to the widely tested (galenic) literature preparation. Availability of a specific formulation for the treatment of this condition may be clinically useful.

Idiopathic megarectum complicating pregnancy: report of a case

Pregnancy often exacerbates constipation in young women with chronic constipation syndromes. The presence of the fetus presents a challenge in both the diagnosis and treatment of these syndromes. This study was conducted to report a rare case of idiopathic megarectum complicating a pregnancy. An aggressive polyethylene glycol (PEG) regimen allowed the patient to carry the child to term and to have a normal vaginal delivery. Successful proctocolectomy was performed with coloanal anastomosis 3 months postpartum. The patient has been free of constipation for 18 months without the need for cathartics or laxatives. All efforts to avoid operative intervention should be made in constipated patients during pregnancy. This principle holds true even in the setting of dilated large bowel. Idiopathic megarectum and the management of constipation in pregnancy are discussed.

Vertical reduction rectoplasty: a new treatment for idiopathic megarectum

BACKGROUND

The aetiology of idiopathic megarectum is unknown and the results of surgery are often unsatisfactory. Rectal hyposensation is common and poor perception of rectal filling may contribute to the poor evacuatory function. By reducing the capacity of the rectum, it was hypothesized that sensory thresholds to rectal distension and perception of urge to defaecate would be improved.

METHODS

Vertical reduction rectoplasty (VRR) and concomitant sigmoid colectomy was performed on six patients with idiopathic megarectum. Patients were evaluated before and after operation by detailed questionnaire and anorectal physiology. Postoperative rectal compliance was also studied by means of a programmable electronic barostat. Where appropriate, physiological data were compared with those obtained in eight healthy volunteers.

RESULTS

Bowel frequency increased from a preoperative median of 2.5 to 16 per month after operation. Four patients reported improved rectal perception of the urge to defaecate. Thresholds for defaecatory urge and maximum tolerated volume were significantly reduced following VRR (P<0.05). Post-VRR rectal compliance was no different from that in healthy volunteers. Colonic transit time decreased significantly after VRR (P<0.05) and evacuation on proctography increased from a median of 30 per cent to 50 per cent. At a median of 57 weeks' follow-up five of the six patients expressed continued satisfaction with the results.

CONCLUSION

VRR is a new approach to the treatment of idiopathic megarectum. Clinical and physiological studies confirm that it can improve sensory feedback and defaecation. The procedure needs further evaluation as the number of patients undergoing the procedure increases.

Constipation

Most patients with chronic constipation respond to dietary measures, fiber supplements, or laxatives. For those who do not, diagnostic tests of colonic and anorectal function help to select appropriate treatments. Therapeutic options, pharmacologic agents, and surgery, the last resort, are discussed in this article.

Colonic motility in man: features in normal subjects and in patients with chronic idiopathic constipation

The human colon is still a relatively unknown viscus, especially concerning its motor activity. However, in recent years, techniques have been perfected that allow a better understanding of colonic motility, especially through prolonged recording periods. In this way, it has been demonstrated that the viscus contracts according to a circadian trend, is responsive to physiological stimuli (meals, sleep), and features high amplitude, propulsive contractions that are part of the complex dynamic of the defecatory process. These physiological properties and their alterations in patients with chronic idiopathic constipation are reviewed in this article.

Chronic idiopathic constipation: pathophysiology and treatment

Chronic constipation is common in the general population, especially in women, in its idiopathic form. However, confusion still surrounds its definition, despite recent efforts to standardize it. Constipation can be divided in two large subgroups-normal transit and slow transit. The have different pathophysiological bases still not completely understood. Most patients respond to simple therapeutic measures aimed at correcting dietary fiber intake and lifestyle. Others, however, need more aggressive treatment, including laxatives, psychological therapy, and biofeedback. In a few patients with intractable constipation, surgery might be indicated to give relief.