["The gold standard for the diagnosis of Hirschsprung's disease (HSCR) is the pathologic evaluation of a rectal biopsy that demonstrates the absence of ganglion cells and nerve fibre hypertrophy. However, it has been frequently reported that hypertrophic nerves may not be present in some variants like long-segment HSCR, total colonic aganglionosis, premature and very young infants. The aim of this study was to determine this association.", "We performed a retrospective review of the HSCR database at our tertiary care children's hospital from 2000 to 2013. In order to analyse the relationship between the diameter of the nerve fibres and the level of aganglionosis, we classified the patient sample into two groups-fibres ≤40 and >40\xa0μm. The groups were statistically compared with P\xa0<\xa00.05 being significant.", 'Rectal biopsies of 92 patients confirmed as HSCR with definitive operation performed at the same institution were reviewed. The mean nerve diameter was 50.1\xa0μm (range 20-87.5\xa0μm). Nerve fibre diameter ≤40\xa0μm was predictive of transition zone above the sigmoid colon. A specificity of 77.3\xa0% and a likelihood ratio of 2.03 supported this perception. No correlation was noted between nerve fibre diameter and gestational age at birth, birth weight or age at biopsy.'] Does aganglionosis with the absence of hypertrophied nerve fibres predict disease proximal to rectosigmoid colon?