The distal level of normally innervated bowel in long segment colonic Hirschsprung's disease

The definitive surgical management of Hirschsprung's disease (HD) depends on an unambiguous histological diagnosis of bowel aganglionosis, as well as an accurate assessment of its proximal extent from the rectum or 'leveling'. This study aimed to evaluate and compare the transition zone in rectosigmoid and long segment colonic forms of HD. One hundred and fifteen cases of rectosigmoid Hirschsprung's disease (RSHD) and 20 cases of long segment colonic Hirschsprung's disease (LScHD) managed from 1998 to 2008 with a consensus prospective protocol were included in this clinicopathological analysis. In RSHD, the radiologic transition zone (rTZ)/gross appearance at laparotomy correlated with the histological 'leveling' in the majority (96%); the histologic transition zone was also short and predictable. In contrast, the rTZ in LScHD was conclusive in only 53%; overall the radiologic and histological transition zones concurred in only 26%. The histologic transition zone extended proximally for an unpredictable length before normal circumferential innervation was noted. A stringent intraoperative histological evaluation of the colon as outlined is more helpful than radiology to establish the distal level of normally innervated bowel in LScHD and achieve an accurate leveling during a colostomy/pull through.