A straight colo-anal anastomosis induces functional disorders in 80-87% of cases. The complete rectum excision implies the loss of its reservoir function determining the anterior resection syndrome described by Karanjia et al. in 1992 and characterised by an increased number of evacuations, difficulty with evacuation, incontinence to gas or liquid faeces, night leakage and tenesmus . This syndrome improves significantly after one year , but in several studies with long-term follow up, considerable defecatory symptoms persisted. In a study published by Paty et al.  with a 4.3-year median follow-up, the most common symptoms patients complained of were: continence disorders (21% incontinence to gas, 23% minor leak and 5% significant leak), evacuation difficulties (32% fragmented evacuation) and 22% of patients reported 4 or more evacuations a day. The results were then classified as excellent for 28% of patients, good in 28% of patients, poor in 32% and very poor in 12% of cases.
To solve this complex mixture of anus and neo-rectum malfunctions the realisation of a colon reservoir was proposed  (Fig. 4), whose physiologic functions are the same as the iliac pouch made for ileo-anal anastomosis. A J-shaped pouch, initially 10-12 cm in size, determined serious evacuation problems . Its size was then reduced to 5-6 cm in order to achieve a suitable reservoir without damaging the neorectum function . Several prospective randomised studies proved how the functional results of the colo-anal anastomosis with J-shaped reservoir were much better than the ones made with straight colo-anal anastomosis [39-42]. In Ortiz et al. study  on 30 patients, at 1-year follow-up, 38% of patients had normal continence with J-pouch vs. 22% of patients with straight anastomosis and the number of evacuations a day was respectively 2 and 4. Hall-boock and Sjodahl , in a comparative study among patients with J-pouch and a control group, did not find any difference in terms of continence after 1-year follow up; 20% referred evacuation difficulties and needed enemas. When the J-pouch is not feasible because mesentery is too thick or because its insertion into a narrow pelvis is too difficult, it is
then possible to realise another kind of cholic reservoir: the transverse coloplasty . To perform such a reservoir an 8-10-cm long incision must be made on the colon, at about 4-5 cm from the distal extremity, and be transversally sutured. A prospective randomised study proved that coloplasty gives functional results identical to the ones achieved with J-shaped reservoir . A very recent study by Remzi et al.  not only confirms the good functional results achieved by coloplasty, but it also shows a lower percentage of anastomotic dehiscence.
Functional results comparable with those achieved with colo-anal astomosis with J-pouch were reported by Machado et al.  in a randomised perspective study on 100 patients, performing latero-ter-minal colo-anal anastomosis.
Colo-anal anastomosis functional results after intersphincteric resection, with total or partial resection of the internal sphincter, are conflicting in the literature: Holzer et al.  reports very good functional results (88% of fully continent patients) whereas a more recent comparative study by Bretagnol et al.  shows a higher rate of incontinence and a worse quality of life compared to colo-anal anastomosis preserving internal anal sphincter.
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