Problems with repairing gut sphincters malfunctions.

Correcting a gut sphincter malfunction is a difficult problem. Because each sphincter has two opposite functions, that of closure and opening, repairing one there is a risk of damaging the other. Indeed, widening a narrow sphincter, such as lower esophageal sphincter (LES) and anal sphincter, may cause gastroesophageal reflux and fecal incontinence, respectively, whereas narrowing a wide sphincter, may cause a difficult transit. All the corrective treatments for difficult or retrograde transit concerning LES and anal sphincter with their unwanted consequences have been analyzed and discussed. To overcome the drawbacks of sphincter surgical repairs, researchers have devised devices capable of closing and opening the gut lumen, named artificial sphincters (ASs). Their function is based on various mechanisms, hydraulic, magnetic, mechanical , operating through many complicated components, such as plastic cuffs, balloons, micropumps, micromotors, connecting tubes and wires, electromechanical clamps, rechargeable batteries, magnetic devices, elastic bands, Unfortunately, these structures may facilitate the onset of infections and induce a local fibrotic reaction, which may cause device malfunctioning, whereas the compression of the gut wall to occlude the lumen may give rise to ischemia with erosions and other lesions. Some ASs are already being used in clinical practice, despite their considerable limits, while others are still at the research stage. In view of the adverse events of the ASs mentioned above, we considered applying bioengineering methods to analyze and resolve biomechanical and biological interaction problems with the aim to conceive and build efficient and safe biomimetic ASs.