Introduction
Rectal sensitivity is most frequently assessed by elastic balloon distension to a maximum tolerated volume, as determined by the patient. In clinical practice, some of the more commonly used systems to assess rectal sensitivity include the Laborie water-perfused manometry system (LWP, balloon volume 400mL) and the Medtronic solid-state 3D manometry system (MSS, balloon volume 400mL). There are no studies that compare diagnostic yield, as defined by the London Classification[1], from these two independent systems.
Aims & Methods
This retrospective service evaluation investigates whether the proportion of diagnostic yield for disorders of rectal sensation differed between two commonly utilised rectal sensitivity measurement methods.
Rectal sensitivity data was collected from 200 patients at the same hospital site, with 100 consecutive patients undergoing rectal sensitivity testing with the LWP system and 100 consecutive patients assessed with the MSS system. Standard investigative protocols were followed, and balloon inflation rate was 2mL/s for both systems[1]. Reference ranges for each system were based on published studies[2-3]. The elastic balloon volume (mL) at each sensory threshold (first sensation volume, desire to defecate volume, and sustained urgency volume), diagnosis of disorders of rectal sensation according to the London Classification, and patient reported predominant symptom was assessed (urgency +/-incontinence, passive incontinence, obstructive defecation syndrome (ODS)/constipation, or anal pain).
Results
In total, rectal sensitivity data from 200 patients was collected (LWP: 100 patients 90F, MSS: 100 patients 91F), and there were no significant differences between sex per cohort (p=1.00). There were no significant differences in the proportions of patient reported predominant symptom per cohort: urgency +/-incontinence (41 LWP, 42 MSS), passive incontinence (23 LWP, 23 MSS), ODS/constipation (33 LWP, 31 MSS), and anal pain (3 LWP, 4 MSS), (p=0.99).
There were significant differences in the proportions of London Classification diagnoses obtained between the two systems: rectal hypersensitivity (9 LWP, 64 MSS), rectal hyposensitivity (3 LWP, 26 MSS), borderline rectal hyposensitivity (5 LWP, 4 MSS), rectal hypersensitivity and rectal hyposensitivity (0 LWP, 4MSS), no disorder of rectal sensation (83 LWP, 2 MSS) (p<0.001).
Conclusion
Despite there being similar patient cohorts in relation to proportions of sex and predominant bowel symptom, there was a significant difference in diagnoses based on London Classifications obtained by the LWP and MSS systems. A large proportion of patients tested using the LWP system had no disorder of rectal sensation, conversely the MSS system reported a much larger proportion of patients with rectal hypersensitivity. As most patients reported urgency +/- incontinence as their predominant symptom, it is plausible that rectal hypersensitivity is a common finding in this patient cohort.
The diagnostic accuracy of the London Classification is likely dependant on the system used and the available published reference values. Accurate assessment of rectal sensitivity can be valuable in guiding effective management of patients with rectal sensitivity disorder. Thus, this data indicates comparative studies using different systems to reduce discrepancies of diagnoses are required to improve clinical management[4].
References
[1] Carrington, E.V. et al. Expert consensus document: Advances in the evaluation of anorectal function. Nature Reviews Gastroenterology and Hepatology. 2018. 15(5): p309-323.
[2] Mion, F. et al. 3D High-definition anorectal manometry: Values obtained in asymptomatic volunteers, fecal incontinence and chronic constipation. Results of a prospective multicenter study (NOMAD). Neurogastroenterol Motil. 2017 Aug;29(8).
[3] Townsend, D.C. et al. Pathophysiology of fecal incontinence differs between men and women: a case-matched study in 200 patients. Neurogastroenterol Motil. 2016 Oct;28(10):1580-8.
[4] Chiarioni, G. et al. Sensory retraining is key to biofeedback therapy for formed stool fecal incontinence. American Journal of Gastroenterology. 2002. 97(1): p109-117.