A Novel Method for Identifying the Transition Zone in Long-Segment Hirschsprung Disease: Investigating the Muscle Unit to Ganglion Ratio

Abstract

Hirschsprung disease (HSCR) is characterised by the absence of enteric ganglia along variable lengths of the distal bowel. Current gold standard treatment involves the surgical resection of the defective, aganglionic bowel. Clear and reliable distinction of the normoganglionated bowel from the transition zone is key for successful resection of the entire defective bowel, and the avoidance of subsequent postoperative complications. However, the intraoperative nature of the tissue analysis and the variability of patient samples, sample preparation, and operator objectivity, make reproducible identification of the transition zone difficult. Here, we have described a novel method for using muscle units as a distinctive landmark for quantifying the density of enteric ganglia in resection specimens from HSCR patients. We show that the muscle unit to ganglion ratio is greater in the transition zone when compared with the proximal, normoganglionated region for long-segment HSCR patients. Patients with short-segment HSCR were also investigated, however, the muscle unit to ganglion ratio was not significantly different in these patients. Immunohistochemical examination of individual ganglia showed that there were no differences in the proportions of either enteric neurons or glial cells through the different regions of the resected colon. In addition, we identified that the size of enteric ganglia was smaller for patients that went on to develop HSCR associated enterocolitis; although the density of ganglia, as determined by the muscle unit to ganglia ratio, was not different when compared with patients that had no further complications. This suggests that subtle changes in the enteric nervous system, even in the “normoganglionated” colon, could be involved in changes in immune function and subsequent bacterial dysbiosis.

Development of the aganglionic colon following surgical rescue in a cell therapy model of Hirschsprung disease in rat

“…It could indicate that signals that direct these axons to their targets are deficient. As in the human disease, there were increased numbers of goblet cells and an increase in EEC numbers in the mucosa of the aganglionic region, but, overall, tissue histology was normal as has been previously observed in humans ( Thiagarajah et al, 2014 ; Kapur, 2016 ; Yang et al, 2022 ). Thus, the Ednrb −/− Hirschsprung disease model in rat appears to be representative of Hirschsprung disease in general.…”

“…Histological investigation showed that the cellular components of all tissue layers were normal. This parallels the situation in humans, where it is difficult to recognize differences between ganglionic and aganglionic regions, or between healthy colons and colons from Hirschsprung patients, except by close examination of the ganglia and the innervation of the colon ( Kapur, 2016 ; Yang et al, 2022 ). We found that the thickness of the external muscle was similar for the ganglionic and aganglionic regions, but the distal region failed to grow in diameter and a considerable size mismatch was apparent by 12 weeks after surgery.…”

Neuroimmune regulation in Hirschsprung’s disease associated enterocolitis

“…In addition, it has been found that the size of the muscle unit/neuron ratio can be used to determine the transition zone of long-segment congenital megacolon, which can better determine the area of surgical resection. The type and content of mucosal nerve fibers and the size of the intestinal ganglion in the intraoperatively resected intestine can also be used as predictors to determine the probability of enterocolitis after HSCR ( 18 , 90 ).…”