ANTERIOR RESECTION SYNDROME IS SECONDARY TO SYMPATHETIC DENERVATION

The mechanism of faecal incontinence following low anterior resection (LAR) has been speculative and the role of disordered neorectal dynami cs difficult to quantify. Using a new methodology which quantifies rec tal response to rapid and ramp inflation, in combination with anal phy siology, we have evaluated 25 LAR-7 with major incontinence and 5 with minor incontinence. The three groups had comparable age, duration pos t surgery and anastomotic distance from the puborectalis. The resting anal canal pressure (RAP) did not related to the anastomotic distance (R(2)=0.09). With the anastomosis at and below 3 vms from the puborect alis, the rectoanal inhibitory reflex (RAIR) was a sustained drop in t he mid anal canal pressure, in contrast to the normal pattern of recov ery above this level. Major incontinence was characterised by a subnor mal anal defence, hypersensitive neorectal dynamics and high amplitude contractile wave while minor incontinence was characterised by a hype rnormal anal defence and a lesser degree of neorectal hypersensitivity . The mathematical viscoelastic rectal model, defined an increasing lo ngitudinal smooth muscle tone and a decreasing functional collagen wit h increasing severity of incontinence as well as a high and low circul ar smooth muscle (CSM) tone with major and minor incontinence respecti vely. This correlated with previous in vitro studies on myenteric plex us denervation and localised damage to the inferior mesenteric plexus respectively. Based on the findings in this study, we conclude that ma jor incontinence is secondary to neurotenesis of the inferior mesenter ic ganglia and the hypogastric plexus, whereas minor incontinence repr esents a localised neurotenesis/neuropraxia of the inferior mesenteric plexus.