Apparatus for the aspiration of a fluid from an individual, the apparatus comprising a port in fluid communication with the atmosphere; a catheter having a proximal end arranged to be inserted into the body of an individual and having a distal end; a one-way valve; and a fluid passage switch reversibly movable between a first position in which the distal end of the catheter is in fluid communication with the port and a second position in which the distal end of the catheter is in fluid communication with the one-way valve, the one-way valve being arranged to permit fluid flow there through ina direction from the distal end of the catheter. The apparatus may be used for both the aspiration of fluid from within the body and instillation of fluid into the body.