Introduction
Rectal sensitivity can be assessed by elastic balloon distension (EBD) or rectal barostat test (RBT)[1]. EBD assesses rectal sensitivity to a maximum volume determined by the balloon. In contrast, RBT assesses rectal sensory thresholds relative to an individual’s total rectal capacity, and can additionally measure intra-rectal pressure. There are no studies that compare diagnostic yield for disorders of rectal sensation, defined by the London Classification[2], using EBD and RBT.
Aims & Methods
This prospective study assessed the feasibility, tolerability, and diagnostic agreement of EBD and RBT in a symptomatic population (Rectal barostat study, ISRCTRN 46893, recruitment ongoing).
Prospective patients referred for anorectal physiology studies were recruited from two NHS Trust sites (UK). Participants underwent both EBD and RBT in randomised order. At site 1 EBD was performed using a Laborie water-perfused manometry system (LWP, balloon volume 400mL). At site 2 the Medtronic solid-state 3D manometry system was applied (MSS, balloon volume 400mL). At both sites the Mui Scientific Rapid Barostat was used for comparison (RBT, bag volume 700mL). Standard protocols for EBD and RBT were followed[3,7]. Reference ranges for each rectal sensitivity test were based on published studies[4-7]. Diagnosis based on the London Classification was obtained using results from both the EBD and RBT. Participants completed a questionnaire to assess tolerability of both procedures.
Results
At site 1 patient uptake of the study was 76% (n=16, 10F:5M, median age 64). At site 2 patient uptake of the study was 45% (n=9, 8F:1M, median age 70). 1 participant from both sites withdrew from the study. 1 participant reported pain during EBD, and 2 during RBT. 2 participants reported that they would not be willing repeat the tests. Median time taken to perform each procedure was 1min24s for EBD and 15min26s for RBT.
The percentage of London Classification diagnoses that remained unchanged was 13% at site 1 and 56% at site 2.
ICC demonstrated good test-retest reliability of the RBT for all sensory thresholds, including ‘first sensation’ (k=0.84, p<0.001), ‘normal desire to defecate’ (k=0.84, p<0.001), and ‘sustained urgency’ (k=0.86, p<0.001).
Conclusion
Patient willingness to be entered into the study differed between sites despite the recruitment process and study team remaining the same. This may be due to differences in patient demographics between sites. Both the EBD and RBT were feasible and well tolerated by participants, however the RBT protocol was significantly longer. Good test-retest reliability of the RBT suggests the protocol could be reduced to one round of sensory testing.
These preliminary findings suggest that agreement between London Classification diagnoses obtained using EBD and RBT is sub-optimal. This was evident in both the LWP and MSS systems. Further studies would be required to determine whether the management of patients with rectal sensitivity disorders based on the London Classification depends on the type of equipment used to assess rectal sensitivity disorders. This is important as accurate assessment of rectal sensitivity may be valuable in guiding effective management of patients with rectal sensitivity disorders[8].
References
[1] Scott, S.M. et al. Rectal sensorimotor dysfunction in constipation. Best Practice and Research Clinical Gastroenterology. 25(1): p103-118.
[2] 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.
[3] Carrington E.V. et al. The international anorectal physiology working group (IAPWG) recommendations: Standardized testing protocol and the London classification for disorders of anorectal function. Neurogastroenterol Motil. 2020 Jan;32(1):e13679.
[4] 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).
[5] 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.
[6] Fox, M. Barostat measurement of rectal compliance and capacity. Dis Colon Rectum. 2006 Mar;49(3):360-70.
[7] Sauter, M. et al. Toward more accurate measurements of anorectal motor and sensory function in routine clinical practice: validation of high-resolution anorectal manometry and Rapid Barostat Bag measurements of rectal function. Neurogastroenterol Motil. 2014 May;26(5):685-95.
[8] 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.
