The Anterior Resection Syndrome (ARS) is characterised by continence disorder, ranging from the inadvertent and uncontrollable passage of flatus to frank faecal incontinence, as well as urgency and increased frequency of evacuation. This syndrome may affect up to 90% of patients with straight colo-
anal reconstruction and may worsen the quality of life in about 39% of them [15,17].
The symptoms are more common in the early post-operative period, when post-operative chemotherapy or irradiation are often necessary, and improve progressively within one year.
A combination of factors seems to influence the incidence and the severity of ARS:
• The length of residual rectal stump plays an important role in determining functional outcome after surgery: anastomoses under 4 cm from the anal verge are often associated with a high incidence of ARS [15,19].
• Patients with anastomotic leakage after surgery show worse anal function as the result of sepsis at the site of anastomosis and pelvic fibrosis .
• Adjuvant chemotherapy or irradiation predispose to ARS or can make its symptoms worse .
• Pre-operative sphincter function, especially a reduced anal canal mean resting pressure (MRP), can predict patients who may have post-operative continence problems: a comprehensive continence history and physical examination completed by anal manometry and ultrasonography should be recommended, particularly in women, in order to identify cases with high ARS risk [1, 21].
A number of functional studies have been undertaken to identify physiological abnormalities following AR, but several misconceptions about the mechanism underlying ARS still exist.
The urgency and the increased frequency of evacuation can be a consequence of the reduction in large intestinal length and of the denervation of mobilised bowel resulting in a more liquid effluent reaching the anal canal .
However, ARS may be also due to damage to the sphincter complex, produced by inserting the stapling device, or the anal retractor, or by injuring the internal anal sphincter during rectal mobilisation, as suggested by significant reduction in anal canal MRP [15,17].
Other evocated causes of poor clinical function are the loss of normal anorectal sensation and the reduced rectal capacity and compliance. Manometric studies support this view, showing a reduction of threshold volume (TV) and of maximum tolerable volume (MTV) as well as a persistent absence of the recto-anal inhibitory reflex (RAIR) in 40-70% of cases [22,23]. As a consequence of the reduced rectal capacity and of the enhanced rigidity of the neorec-tum, a high-pressure zone is created in the upper part of the anal canal until the sphincter mechanism is overcome. This is confirmed by the evidence that the MTV of the neorectum is inversely correlated to the urgency and the high frequency of evacuation [17, 22].
The idea for the creation of a colonic reservoir, based on the experience of ileal pouches, appeared therefore attractive, especially to increase neorectal capacity and, more recently, also to dissipate the high intraluminal pressure generated within a non-compliant colon.
The procedure that has gained most popularity is the colonic J-pouch reconstruction, although other kinds of reservoirs have been described and some of them are spreading too.
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