The aim of this study was to determine if nitric oxide (NO) is the non-adrenergic, noncholinergic neurotransmitter, released by enteric inhibitory nerves, which mediates relaxation ofthe human internal anal sphincter. Isolated muscle strips were mounted for isometric tension recording in superfusion organ baths. Sodium nitroprusside, an exogenous donor of NO, relaxed the strips in a concentration dependent manner. In the presence of atropine and guanethidine, transmural field stimulation produced tetrodotoxin sensitive relaxations, which were inhibited in a dose dependent and enantiomer specific manner by antagonists of NO synthase; completely by L-nitroarginine and partially by L-N-monomethyl arginine. The effect of these antagonists was reversed by L-arginine but not D-arginine. Oxyhaemoglobin, a scavenger of nitric oxide, also abolished the relaxations but methaemoglobin had no such effect. These results strongly suggest that NO is, or is very closely associated with, the non-adrenergic, non-cholinergic neurotransmitter mediating neurogenic relaxation of the human internal anal sphincter. (Gut 1993; 34: 689-693) in nerve mediated relaxation of the internal anal sphincter.2"25Nitric oxide is synthesised from L-arginine in a reaction catalysed by NO synthase. This enzyme exhibits a high degree of substrate specificity (NO is not produced from Darginine) and is dependent on several cofactors, among which are Ca2+, calmodulin, and reduced nicotinamide adenine dinucleotide phosphate. Nitric oxide is freely soluble, diffuses rapidly, and has a short half life (three seconds), being inactivated by formation of NO3-after contact with the superoxide anion, 02-It exerts its effects by binding to cytosolic guanylate cyclase and stimulating the production of cyclic guanosine monophosphate.In humans, the hypothesis that NO is an inhibitory neurotransmitter in the internal anal sphincter is based on results presented in a brief report,25 which showed that N-nitro-L-arginine, a potent antagonist of NO synthase, abolished NANC nerve mediated relaxation in isolated sphincter tissue. We have investigated the involvement of NO in greater detail and have examined the effects of exogenous NO, inhibitors ofNO synthase, and oxyhaemoglobin, a scavenger of NO, on the behaviour of isolated strips of human internal anal sphincter in vitro. Implausible as it might seem at first, there is now good evidence that nitric oxide (NO) is an important endogenous bioactive substance.7"9 It has been identified as a neurotransmitter in the gastrointestinal tract,9'"9 and has been implicated Methods Sphincter tissue was taken from patients (four men, seven women; median age 69 (range 57-82) years) undergoing abdominoperineal resection of the rectum and anal canal for low lying rectal carcinoma. With a dissecting microscope, the epithelium of the anal canal was removed together with the submucosa. Strips of the distal internal anal sphincter measuring I x 1 x 10 mm and containing parallel muscle bundles were prepared and mounted for isome...

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Pouch-vaginal fistula is a rare complication following restorative proctocolectomy. Seven patients who developed such a fistula are presented. Six pouch-vaginal fistulas occurred at the level of the pouch-anal anastomosis and one 3 cm above the anastomosis, level with the posterior vaginal fornix. The anastomosis had been hand-sewn in four patients (following mucosectomy) and stapled in three. Five fistulas presented within the perioperative period (median 16 (range 10-30) days) and two at 186 and 273 days. Treatment was successful in the patients who presented early, and these remain continent with functioning pouches. If not already present (two patients), an ileostomy was raised. Repair was by endovaginal flap advancement, combined with fistulotomy and sphincter repair in two patients. Treatment was unsuccessful in the two patients who presented late; in both the diagnosis was revised to Crohn's disease, necessitating pouch excision.

The outcome of suprapubic and urethral catheterization in abdominal surgery was compared in a prospective randomized trial. Twenty-eight patients received a suprapubic and 29 a urethral catheter. The groups were similar in terms of age, sex, operation performed and postoperative analgesia. There was no difference in the duration of catheterization (suprapubic: median 5 (range 4-10) days; urethral: median 4 (range 2-11) days). Urinary sepsis occurred in three patients in each group. Urethral catheters caused pain in significantly more patients (urethral 13; suprapubic two; chi 2 = 8.6, 1 d.f. P < 0.01), on more days (suprapubic: 6 of 142 catheter days; urethral: 37 of 126 catheter days; chi 2 = 29.5, 1 d.f. P < 0.001). Two men with urethral catheters and one with a suprapubic catheter failed to void urethrally when required to do so. Suprapubic catheterization is the method of choice for urinary drainage when this is required in abdominal surgery.

Following successful colonic pouch formation, routine study of the pouch by contrast radiology does not add to clinical assessment. As a consequence radiological imaging is unnecessary and can be omitted.