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The proximity of the very low rectum rectal cancer to the anal sphincter raises a specific problem: how and until when can we preserve the anal continence without compromising the oncological result of the tumor resection? In this situation, intersphincteric resection (ISR) offers an excellent alternative to abdominoperineal resection (APR), but the selection of patients for this option must be extremely precise. This complex choice justifies the simultaneous consideration of an oncological approach with a functional approach in order to provide a full benefit to the patient. When a circumferential resection margin of at least 1 mm can be performed with a distal resection margin of at least 1 cm with or without preoperative radiotherapy, ISR ensures a safety choice. The oncological results of ISR reported in the literature when performed properly found a 5-year disease-free survival of 80.2% with a local recurrence rate of only 5.8%. In parallel to this oncological evaluation, the expected post-operative functional outcome and the resulting quality of life must be properly assessed pre-operatively, since partial or total resection of the internal sphincter impacts significantly on the functional outcome. Based on data from the literature, this work reports the essential anatomical considerations and then the oncological and functional elements indispensables when an anal continence preservation is evoked for a tumor of the very low rectum. Finally, the precise selection criteria and the major surgical principles are outlined in order to guarantee the safety of this modern choice for the patient.

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Background Fistulizing anoperineal lesions (FAPLs) are common and severe complications of Crohn’s disease (CD), exposing patients to the risk of anal sphincter alteration and permanent stoma. Due to the limited efficacy of current treatments, identifying new local therapies is mandatory. However, testing new treatments is currently limited because no relevant preclinical model of Crohn’s-like FAPL is available. Thus, a reliable and reproducible experimental model of FAPLs is needed to assess new therapeutic strategies. Methods Twenty-one rats received a rectal enema of 2,4,6-trinitrobenzensulfonic acid (TNBS) to induce proctitis. Seven days later, a transsphincteric fistula tract was created with a surgical thread, instilled with TNBS twice a week until its removal at day 7 (group 1), day 14 (group 2), or day 28 (group 3). In each rat, pelvic MRI was performed just before and 7 days after thread removal. Rats were sacrificed 7 days after thread removal for pathological assessment of the fistula tract. Results The optimal preclinical model was obtained in group 3. In this group, 7 days after thread removal, all animals (9 of 9) had a persistent fistula tract visible on MRI with T2-hypersignal (normalized T2 signal intensity: 2.36 ± 0.39 arbitrary units [a.u.] [2.08–2.81]) and elevation of the apparent diffusion coefficient (1.33 ± 0.16 10-3 millimeter squared per seconds [1.18–1.49]). The pathological examination of the fistula tract revealed acute and chronic inflammation, granulations, fibrosis, epithelialization, and proctitis in the adjacent rectum. Conclusions This reproducible preclinical model could be used to assess the effectiveness of innovative treatments in perianal fistulizing CD.

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