A multi-lumen catheter (450, 530, 600) insertable into a patient for monitoring pressure within a body cavity without insertion of fluid into the body cavity, the catheter comprising: a shaft having at least first, second and third lumens formed therein; an expandable outer balloon (456, 514, 546, 606) at a distal portion of the catheter, the outer balloon being configured to be partially inflated through the first lumen (486, 528, 642), the outer balloon having a first outer wall and movable from a first condition to a more expanded condition; a wall provided between the outer balloon and an inner balloon (458, 510, 538, 608), the wall having at least one side opening (462, 494, 644a); the second lumen being a drainage lumen (484, 524, 532, 646) configured to communicate with a patient's bladder, the drainage lumen having a side opening (463, 520, 610) for removal of fluid from the bladder; wherein the inner balloon (458, 510, 538, 608) is configured to be partially inflatable independent of the first outer balloon inflating lumen and movable from a first condition to a more expanded condition, the inner balloon positioned within the outer balloon and having a second outer wall (458b, 540, 608a) and a gas containing chamber, the second outer wall of the inner balloon radially spaced from the first outer wall of the outer balloon, the inner balloon having an elongated portion (459b, 512, 542, 609) extending at least partially proximally through the third lumen of the catheter for inflation of the inner balloon, the outer balloon acting as a medium for transfer of fluid within the outer balloon to a second outer wall of the inner balloon to deform the inner balloon for monitoring fluid pressure; wherein in response to pressure exerted on the first outer wall of the expanded outer balloon, fluid within the outer balloon enters the at least one side opening (462, 494, 644a) in the wall between the outer balloon and the inner balloon to exert a pressure on the second outer wall of the inner balloon to deform the inner balloon and compress the gas within the inner balloon to provide a pressure measurement; the catheter further comprising a pressure sensor communicating with the gas containing chamber for measuring pressure based on compression of gas caused by deformation of the expanded inner balloon resulting from deformation of the expanded outer balloon, the pressure sensor being configured to measure pressure at multiple times during a procedure without injecting fluid within the body cavity as the outer balloon provides the fluid transfer medium. a shaft having at least first, second and third lumens formed therein; an expandable outer balloon (456, 514, 546, 606) at a distal portion of the catheter, the outer balloon being configured to be partially inflated through the first lumen (486, 528, 642), the outer balloon having a first outer wall and movable from a first condition to a more expanded condition; a wall provided between the outer balloon and an inner balloon (458, 510, 538, 608), the wall having at least one side opening (462, 494, 644a); the second lumen being a drainage lumen (484, 524, 532, 646) configured to communicate with a patient's bladder, the drainage lumen having a side opening (463, 520, 610) for removal of fluid from the bladder; wherein the inner balloon (458, 510, 538, 608) is configured to be partially inflatable independent of the first outer balloon inflating lumen and movable from a first condition to a more expanded condition, the inner balloon positioned within the outer balloon and having a second outer wall (458b, 540, 608a) and a gas containing chamber, the second outer wall of the inner balloon radially spaced from the first outer wall of the outer balloon, the inner balloon having an elongated portion (459b, 512, 542, 609) extending at least partially proximally through the third lumen of the catheter for inflation of the inner balloon, the outer balloon acting as a medium for transfer of fluid within the outer balloon to a second outer wall of the inner balloon to deform the inner balloon for monitoring fluid pressure; wherein in response to pressure exerted on the first outer wall of the expanded outer balloon, fluid within the outer balloon enters the at least one side opening (462, 494, 644a) in the wall between the outer balloon and the inner balloon to exert a pressure on the second outer wall of the inner balloon to deform the inner balloon and compress the gas within the inner balloon to provide a pressure measurement; the catheter further comprising a pressure sensor communicating with the gas containing chamber for measuring pressure based on compression of gas caused by deformation of the expanded inner balloon resulting from deformation of the expanded outer balloon, the pressure sensor being configured to measure pressure at multiple times during a procedure without injecting fluid within the body cavity as the outer balloon provides the fluid transfer medium.