Anal sphincter function in conservatively managed rectal intussusception at long-term follow-up: A prospective anal acoustic reflectometry study with comparison to healthy volunteer data.

Abstract

Rectal intussusception (RI), proposed to be a progressive condition, is associated with internal sphincter dysfunction. This study examines sphincter function using anal acoustic reflectometry (AAR) at long-term follow-up. A prospective study of conservatively managed patients attending a tertiary pelvic floor unit. Clinical, AAR and symptom severity data were analysed at baseline and follow-up (>5 years). Patients were grouped into intra-rectal (Oxford I-II) or intra-anal RI (III-IV). Data from asymptomatic volunteers were used to estimate the effect of ageing on AAR parameters. Twenty-nine patients (27 female; median age: 66 years) were recruited, with follow-up at a median of 66 (IQR: 64-67) months. Twelve were diagnosed with intra-rectal RI and 17 with intra-anal RI at baseline. No patient developed an external rectal prolapse. There were no differences in quality of life, faecal incontinence or constipation symptoms in either group at follow-up (p > 0.05). A non-significant decrease in opening pressure, a measure of internal sphincter function, was seen in both intra-rectal (-4.0 cmH₂O; p = 0.530) and intra-anal RI (-3.7 cmH₂O; p = 0.287). In healthy volunteers, opening pressure was associated with age (r = -0.402; p < 0.001) and a decline of 2.90 cmH₂O (95% CI: -4.35 to -1.50) would be expected after 5 years. Incremental squeeze opening pressure showed a non-significant increase in intra-rectal RI (8.4 cmH₂O; p = 0.099) and no change in intra-anal RI (-1.7 cmH₂O; p = 0.532). There were no significant changes in patient-reported symptoms or anal sphincter function in conservatively managed RI at follow-up, challenging the concept of a progressive condition with a detrimental impact on sphincter function.