A device for performing resection of an organ in a cavity of a living body, in particular of a human being, known by the term "resectoscope", and comprising at least: • a guide defined between a proximal end and a distal end, said guide defining a duct that is open at both its proximal end and its distal end, said guide being constituted at least by a first cylindrical tube and by a second cylindrical tube, the second tube being mounted in the first tube; • at least one electrical conductor surrounded by a sheath (33, 34) made of electrically insulating material, said electrical conductor as insulated in this way (31, 32) being mounted in said duct; and • inlet/outlet means mounted in cooperation with the proximal end of said guide; the device being characterized by the facts that: • said first tube is a cylinder of revolution having an inside radius of value R1; • said second tube comprises: * a first portion being a portion of a cylinder of revolution having a center angle of value Ac and an outside radius of value R2, where R2 is less than R1; and * a second portion that is a portion of a cylinder that is not a cylinder of revolution and having an angle at the center of value "360° - Ac", the two edges (222-1, 222-2) of the second portion of the second tube being in continuity respectively with the two edges of the first portion of the second tube; • said insulated conductor (31, 32) being mounted in contact on said second portion of said second tube between the outside wall of the second tube and the inside wall of the first tube; and • that it further includes means for holding said insulated conductor (31, 32) in contact on said second portion of the second tube. • a guide defined between a proximal end and a distal end, said guide defining a duct that is open at both its proximal end and its distal end, said guide being constituted at least by a first cylindrical tube and by a second cylindrical tube, the second tube being mounted in the first tube; • at least one electrical conductor surrounded by a sheath (33, 34) made of electrically insulating material, said electrical conductor as insulated in this way (31, 32) being mounted in said duct; and • inlet/outlet means mounted in cooperation with the proximal end of said guide; • said first tube is a cylinder of revolution having an inside radius of value R1; • said second tube comprises: * a first portion being a portion of a cylinder of revolution having a center angle of value Ac and an outside radius of value R2, where R2 is less than R1; and * a second portion that is a portion of a cylinder that is not a cylinder of revolution and having an angle at the center of value "360° - Ac", the two edges (222-1, 222-2) of the second portion of the second tube being in continuity respectively with the two edges of the first portion of the second tube; * a first portion being a portion of a cylinder of revolution having a center angle of value Ac and an outside radius of value R2, where R2 is less than R1; and * a second portion that is a portion of a cylinder that is not a cylinder of revolution and having an angle at the center of value "360° - Ac", the two edges (222-1, 222-2) of the second portion of the second tube being in continuity respectively with the two edges of the first portion of the second tube; • said insulated conductor (31, 32) being mounted in contact on said second portion of said second tube between the outside wall of the second tube and the inside wall of the first tube; and • that it further includes means for holding said insulated conductor (31, 32) in contact on said second portion of the second tube.