L i

Colo-anal LAR C-pouch

Fig. 7. The anal pressures after the three different rectal reconstructions show no significant differences

Fig. 8a-e. a Anal probe used for the EMG acquisitions. The probe carries an array of 16 silver electrodes equally spaced along a circumference. b Representation of the anatomical configuration of the external anal sphincter of a female subject at 1 cm inside the anal orifice. Such configuration was obtained after a visual inspection of the EMG signals shown in c. c EMG signals detected with the anal probe at 1 cm depth inside the anal orifice of a female subject. d Representation of the anatomical configuration of the external anal sphincter of a male subject at 1 cm inside the anal orifice. Such configuration was obtained after a visual inspection of the EMG signals shown in e. e EMG signals detected with the anal probe at 1 cm depth inside the anal orifice of a male subject. The different architectures of the muscles are evident. Case b shows a sphincter with innervation in both hemi-sphincters, while case d shows a sphincter with innervation in only one hemi-sphincter. In case b damage of one innervation zone would make the sphincter asymmetric, while in case d damage of the innervation zone would likely denervate the sphincter and result in incontinence. Very large interindividual variability has been observed. No standard innervation pattern has been found [20, 35]

Fig. 8a-e. a Anal probe used for the EMG acquisitions. The probe carries an array of 16 silver electrodes equally spaced along a circumference. b Representation of the anatomical configuration of the external anal sphincter of a female subject at 1 cm inside the anal orifice. Such configuration was obtained after a visual inspection of the EMG signals shown in c. c EMG signals detected with the anal probe at 1 cm depth inside the anal orifice of a female subject. d Representation of the anatomical configuration of the external anal sphincter of a male subject at 1 cm inside the anal orifice. Such configuration was obtained after a visual inspection of the EMG signals shown in e. e EMG signals detected with the anal probe at 1 cm depth inside the anal orifice of a male subject. The different architectures of the muscles are evident. Case b shows a sphincter with innervation in both hemi-sphincters, while case d shows a sphincter with innervation in only one hemi-sphincter. In case b damage of one innervation zone would make the sphincter asymmetric, while in case d damage of the innervation zone would likely denervate the sphincter and result in incontinence. Very large interindividual variability has been observed. No standard innervation pattern has been found [20, 35]

complex, leading to a longer standing presence of symptoms. Post-operative pelvic radiotherapy has significant adverse effects on anorectal function, with higher rates of clustering and frequency of defecation than with pre-operative radiotherapy [23]. In case of post-irradiation incontinence, the tendency of stools to be liquid for concomitant ileal injury may further aggravate the situation [24]. Stoma closure is not always possible in patients who experienced anasto-motic leakage and, in those who have the stoma closed, impaired long-term anorectal function has to be expected. Evacuation problems with reduced neo-

rectal capacity during manovolumetry (Fig. 3) have been shown [25].

Other factors contributing to the determination of functional disturbances are damage to innervations and trauma to the residual rectal stump and sphincter complex resulting from the wide dissection of perirectal structures [26]. Nerve damage occurs in the superior hypogastric plexus and in the inferior mesenteric plexus during aortic bifurcation dissection manoeuvres, at the inferior mesenteric artery and superior haemorrhoidal artery during the manoeuvres of isolation and section of the mesorectum [27].

Fig. 9. Patient tested before and 14 days after intersphincteric resection for low rectal cancer (4 cm from the anal orifice); major faecal incontinence at the moment of exam. Signals were acquired at three levels from anal verge during maximal voluntary contraction, performed before (Test 1) and after (Test 2) intersphincteric rectal resection. Signal amplitude is lower at 3 cm and 5 cm from the anal verge in the postoperative test, while the EMG activity at 1 cm appears to be similar in both investigations. Few motor unit action potentials (MUAPs) are visible at 5 cm depth over channels 1-8 (right hemi-sphincter) in the signals acquired during the second test, while higher EMG activity in the same region was evident from the first test. This reduction of activity could be due to the intersphincteric resection performed to remove the rectal cancer. (Courtesy of Prof. Mer-letti R LISiN (Laboratory for Engineering of the Neuromuscular System, Torino, Italy)

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