Benzalkonium chloride–treated anorectums mimicked endothelin-3–deficient aganglionic anorectums on manometry Harry H. Qin a , Nanye Lei a , Julianne Mendoza a , James C.Y. Dunn a,b, ⁎ a Department of Surgery, University of California, Los Angeles, CA, USA b Department of Bioengineering, University of California, Los Angeles, CA, USA Received 9 August 2010; accepted 12 August 2010 Key words: Chemical ablation; Lethal spotted; Aganglionosis; Nerve hypertrophy; Anorectal manometry Abstract Background/Purpose: The anorectal spasticity in Hirschsprung disease may be caused by the absence of enteric ganglia and/or the presence of hypertrophic nerves. Anorectal manometry of chemically denervated rectums was compared with that of congenital aganglionic rectums that also possessed hypertrophic nerves. Methods: Aganglionic and ganglionic littermates were produced from breeding heterozygous lethal- spotted mice. Benzalkonium chloride was endorectally injected into ganglionic rectums to ablate the neural elements. Anorectal manometry was performed before the injection and on day 14 postinjection. The anorectal resting pressure was calculated based on the manometric tracing. Rectums were retrieved on day 14 for histologic evaluations. Results: Benzalkonium chloride injection successfully ablated the rectal ganglia. Although ganglionic littermates exhibited regular slow waves on anorectal manometry, aganglionic lethal-spotted mice showed irregular waves. Similar to lethal spotted mice, benzalkonium chloride–treated mice exhibited significantly higher anorectal resting pressure than that of ganglionic mice. The slow waves were absent in benzalkonium chloride–treated mice. Conclusion: Benzalkonium chloride treatment produced aganglionic rectums that had higher resting pressure similar to the congenital aganglionic rectums. This suggests that hypertrophic nerves in congenital aganglionosis are not necessary to produce the anorectal spasticity. n 2010 Elsevier Inc. All rights reserved. Hirschsprung disease is characterized by aganglionosis in both the submucosal and myenteric plexuses secondary to the absence of the enteric nervous system, with concurrent hypertrophic nerve trunks thought to mainly originate from extrinsic, parasympathetic nerves [1,2]. Patients usually have increased anorectal resting pressure (ARP) and do not possess rectoanal inhibitory reflex on manometry [3]. The spastic contraction in the aganglionic segment can be attributed either to the lack of smooth muscle relaxants, including nitric oxide, vasoactive intestinal peptide, and carbon monoxide from nonadrenergic, noncholinergic neu- rons [4-6], or to the excessive activity of excitatory acetylcholine and substance P released from hypertrophic nerves [7,8]. It remains unclear whether the absence of the relaxants or the presence of the excessive excitants ⁎ Corresponding author. UCLA Division of Pediatric Surgery, Box 709818, Los Angeles, CA 90095, USA. Tel.: +1 310 206 2429; fax: +1 310 206 1120. E-mail address: jdunn@mednet.ucla.edu (J.C.Y. Dunn). www.elsevier.com/locate/jpedsurg 0022-3468/$ – see front matter n 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2010.08.045 Journal of Pediatric Surgery (2010) 45, 2408–2411