A tissue resecting instrument , comprising: a housing defining an interior; a shaft (130; 530; 630; 730) rotatable relative to the housing and extending distally from the housing , the shaft (130; 530; 630; 730) defining a proximal end portion disposed within the interior of the housing , a distal end portion distally-spaced from the housing , and a lumen extending therethrough, the lumen disposed in fluid communication with the interior of the housing ; a cutting member (140; 540; 640; 740) operably associated with the distal end portion of the shaft (130; 530; 630; 730) to enable tissue resection upon rotation of the shaft (130; 530; 630; 730); a turbine (152; 852; 952) disposed within the interior of the housing and operably associated with the proximal end portion of the shaft (130; 530; 630; 730) such that rotation of the turbine (152; 852; 952) rotates the shaft (130; 530; 630; 730) relative to the housing to thereby rotate the cutting member (140; 540; 640; 740), the turbine (152; 852; 952) including a plurality of fins (158; 858; 958); and a fluid outflow tube operably associated with the housing , the fluid outflow tube adapted to connect to a suction source to enable the suctioning of fluid and resected tissue proximally through the lumen of the shaft (130; 530; 630; 730), the interior of the housing , and into the fluid outflow tube , characterised in that the lumen of the shaft (130; 530; 630; 730) communicates with the housing through a plurality of openings defined through the shaft (130; 530; 630; 730) towards the proximal end portion thereof such that proximal fluid flow flows from an operative site, through the lumen, into the housing through the openings , and across the plurality of fins (158; 858; 958) of the turbine (152; 852; 952) to urge the turbine (152; 852; 952) to rotate, thereby rotating the shaft (130; 530; 630; 730) relative to the housing to enable tissue resection with the cutting member (140; 540; 640; 740). a housing defining an interior; a shaft (130; 530; 630; 730) rotatable relative to the housing and extending distally from the housing , the shaft (130; 530; 630; 730) defining a proximal end portion disposed within the interior of the housing , a distal end portion distally-spaced from the housing , and a lumen extending therethrough, the lumen disposed in fluid communication with the interior of the housing ; a cutting member (140; 540; 640; 740) operably associated with the distal end portion of the shaft (130; 530; 630; 730) to enable tissue resection upon rotation of the shaft (130; 530; 630; 730); a turbine (152; 852; 952) disposed within the interior of the housing and operably associated with the proximal end portion of the shaft (130; 530; 630; 730) such that rotation of the turbine (152; 852; 952) rotates the shaft (130; 530; 630; 730) relative to the housing to thereby rotate the cutting member (140; 540; 640; 740), the turbine (152; 852; 952) including a plurality of fins (158; 858; 958); and a fluid outflow tube operably associated with the housing , the fluid outflow tube adapted to connect to a suction source to enable the suctioning of fluid and resected tissue proximally through the lumen of the shaft (130; 530; 630; 730), the interior of the housing , and into the fluid outflow tube , characterised in that the lumen of the shaft (130; 530; 630; 730) communicates with the housing through a plurality of openings defined through the shaft (130; 530; 630; 730) towards the proximal end portion thereof such that proximal fluid flow flows from an operative site, through the lumen, into the housing through the openings , and across the plurality of fins (158; 858; 958) of the turbine (152; 852; 952) to urge the turbine (152; 852; 952) to rotate, thereby rotating the shaft (130; 530; 630; 730) relative to the housing to enable tissue resection with the cutting member (140; 540; 640; 740). <EOS>