Anal achalasia after pull-through operations for Hirschsprung's disease -- preliminary experience with topical nitric oxide.

INTRODUCTION: Following definitive pull-through for Hirschsprung's disease (HD), a minority of patients develop constipation, incontinence and enterocolitis. The cause for these symptoms in some of the patients is believed to be "internal sphincter achalasia" related to abnormal innervation of the sphincter, with an absent anorectal relaxation reflex. Transanal myectomy, posterior sagittal rectal myectomy, anal dilatation and even intrasphincter injection of botulinum toxin have been used to solve this problem. Nitric oxide (NO) has been identified as the chemical messenger of the intrinsic non-adrenergic, non-cholinergic pathway mediating relaxation of the normal internal anal sphincter when applied topically.

BACKGROUND/PURPOSE: To evaluate the effect of topical isosorbide dinitrate (DTN) applied to the anus and its role in the management of patients with HD after pull-through who have ongoing difficulties in stool evacuation.

MATERIAL AND METHODS: Four children, aged 2, 5, 7 and 13 years, who all underwent the Soave operation for Hirschsprung's disease, were assessed. Three patients had recurrent episodes of enterocolitis, and all had symptoms of difficulty in rectal/colonic evacuation. Conservative treatment of repeated anal dilatation under anaesthesia had failed to improve symptoms. A rectal myectomy and conversion of Soave to Duhamel procedure had been done in 2 without significant improvement in symptoms. In all patients, ano-rectal manometry was performed before and after application of DTN paste (1 mg/kg/day in two separate doses) which was continued for a minimum period of 3 weeks. Results. Marked symptom improvement was noted in all 4 children. On manometric assessment the median maximum pressure (pre-DTN application) was 165 mm Hg (range 96 - 250), the median sphincter length 2.7 cm (range 2.3 - 3.1) and the high-pressure zone (HPZ) median length 1.6 cm (range 1.2 - 2.1). After application of DTN paste, the maximum pressure dropped by a median of 88 mm Hg (range 46 - 90), total sphincter length shortened to a median of 2.1 cm and the HPZ by a median total length of 1.4 cm (range 0.01 - 0.9). In addition, vector volume was reduced by a median of 59 % (range 40.5 - 77).

CONCLUSION: From these results, it is evident that DTN paste is not only an adjunct in the investigation, but can also be used as a temporary form of treatment of obstructive symptoms in Hirschsprung's disease patients.