Qualitative and quantitative analysis of rectoanal inhibitory reflex (RAIR) modulation in functional bowel disorders

Anal canal and sphincter function in children with Hirschsprung disease after definitive surgery

INTRODUCTION

Anorectal manometry may be useful to objectively evaluate anorectal function following definitive pullthrough for Hirschsprung Disease (HD) but there is little published data. Our study aims to investigate anorectal manometry findings and their association with bowel function.

METHODOLOGY

This was a prospective observational study. Convenience sampling method was used to recruit all HD patients who had definitive pullthrough from January 2019 to December2020 in our institution. High-resolution anorectal manometry (HRAM) was used to record anal resting pressure (ARP), length of high-pressure zone (HPZ), and presence/absence of recto-anal inhibitory reflex (RAIR). The Paediatric Incontinence/Constipation Scoring System (PICSS) was scored for all participants. PICSS is a validated questionnaire with scores mapped to an age-specific normogram to denote constipation, incontinence, and their combinations. Non-parametric and chi-square tests at significance p<0.05 were conducted to examine the relationship between PICSS categories and manometry findings. Ethical approval was obtained.

RESULTS

There were 32 participants (30 boys). Median age at participation was 26.5 months (range: 13.8-156). Twenty-four (75%) had transanal pullthrough, 8(25%) underwent Duhamel procedure. PICSS scored 10(31.3%) as normal, 8(25%) as constipation, 10(31.3%) as incontinent, and 4(12.5%) as mixed. RAIR was present in 12 patients (37.5%). HPZ, maximum ARP, mean ARP were comparable across all PICSS groups without statistically significant differences. Presence of RAIR was not significantly associated with any PICSS groups (p = 0.13).

CONCLUSION

Bowel function does not appear to be significantly associated with HRAM findings after definitive pullthrough for HD, but our study is limited by small sample size. RAIR was present in 37.5% patients after pullthrough.

LEVEL OF EVIDENCE

Level II.

Diagnostic testing for fecal incontinence

Many tests are available to assist in the diagnosis and management of fecal incontinence. Imaging studies such as endoanal ultrasonography and defecography provide an anatomic and functional picture of the anal canal which can be useful, especially in the setting of planned sphincter repair. Physiologic tests including anal manometry and anal acoustic reflexometry provide objective data regarding functional values of the anal canal. The value of this information is of some debate; however, as we learn more about these methods, they may prove useful in the future. Finally, nerve studies, such as pudendal motor nerve terminal latency, evaluate the function of the innervation of the anal canal. This has been shown to have significant prognostic value and can help guide clinical decision making. Significant advances have also happened in the field, with the relatively recent advent of magnetic resonance defecography and high-resolution anal manometry, which provide even greater objective anatomic and physiologic information about the anal canal and its function.

Morphological abnormalities of the recto-anal inhibitory reflex reflects symptom pattern in neurogenic bowel

BACKGROUND

Bowel dysfunction amongst multiple sclerosis (MS) and spinal cord injury (SCI) patients often manifests as fecal incontinence (FI) or constipation, but the pathophysiology is poorly understood. Anorectal physiology provides an objective assessment of lower bowel functions and is increasingly being used in clinical practice.

AIM

The purpose of this study was to correlate symptoms of bowel dysfunction in patients with spinal cord disease with findings in anorectal physiology. We hypothesized that specific abnormalities will correlate with symptoms: prolonged recto-anal inhibitory reflex in patients with incontinence and decreased rectal mucosal blood flow in patients with constipation.

METHODS

Forty-nine patients with MS (35 with predominant FI and 14 constipation), 46 supraconal SCI (mixed symptom load), and 21 healthy volunteers matched for age and sex were studied. Subjects completed validated constipation and FI symptom questionnaires. Patients underwent standard anorectal physiology, including assessment of rectal mucosal blood flow and recto-anal inhibitory reflex (RAIR).

RESULTS

Severity of constipation correlates significantly with distension sensitivity (urge volume [r = 0.68, p = 0.002] and maximal volume [r = 0.39, p = 0.03]). Severity of constipation also correlated with diminished rectal mucosal blood flow in both patient groups (r = -0.51, p = 0.006). In both groups, constipation correlated with diminished relaxation of the sphincters in the RAIR whilst fecal incontinence correlated with a prolonged duration of RAIR (r = 0.33, p = 0.009) and recovery phase (r = 0.37, p = 0.05).

CONCLUSION

Bowel symptoms in patients with MS and SCI correlate with specific alterations of anorectal physiology. This provides objective assessment of bowel symptoms and may allow tailored treatment to individual patients.