TY - JOUR T1 - Megarectum: systematic histopathological evaluation of 35 patients and new common pathways in chronic rectal dilatation JF - Journal of Clinical Pathology JO - J Clin Pathol SP - 651 LP - 657 DO - 10.1136/jclinpath-2021-207413 VL - 75 IS - 10 AU - Joanne E Martin AU - William English AU - John V Kendall AU - Vinayata Sheshappanavar AU - Sara Peroos AU - Milly West AU - Stewart Cleeve AU - Charles Knowles Y1 - 2022/10/01 UR - http://jcp.bmj.com/content/75/10/651.abstract N2 - Aims Megarectum is well described in the surgical literature but few contemporary pathological studies have been undertaken. There is uncertainty whether ‘idiopathic’ megarectum is a primary neuromuscular disorder or whether chronic dilatation leads to previously reported and unreported pathological changes. We sought to answer this question.Methods Systematic histopathological evaluation (in accord with international guidance) of 35 consecutive patients undergoing rectal excision surgery for megarectum (primary: n=24) or megarectum following surgical correction of anorectal malformation (secondary: n=11) in a UK university hospital with adult/paediatric surgical and gastrointestinal neuropathology expertise.Results We confirmed some previously reported observations, notably hypertrophy of the muscularis propria (27 of 35, 77.1% of patients) and extensive fibrosis (30 of 35, 85.7% of patients). We also observed unique and previously unreported features including elastosis (19 of 33, 57.6%) and the presence of polyglucosan bodies (15 of 32, 46.9% of patients). In contrast to previous literature, few patients had any strong evidence of specific forms of visceral neuropathy (5 of 35, including 3 plexus duplications) or myopathy (6 of 35, including 3 muscle duplications). All major pathological findings were common to both primary and secondary forms of the disease, implying that these may be a response to chronic rectal distension rather than of primary aetiology.Conclusions In the largest case series reported to date, we challenge the current perception of idiopathic megarectum as a primary neuromuscular disease and propose a cellular pathway model for the features present. The severe morphological changes account for some of the irreversibility of the condition and reinforce the need to prevent ongoing rectal distension when first identified.Data are available upon reasonable request. ER -