The invention relates to a connecting piece for establishing a fluid connection between fluid-conducting lines for installation in a cut-out in a housing part of a medical device, in particular a dialysis unit. Furthermore, the invention relates to a medical device, in particular a dialysis unit, comprising a housing that comprises a housing part having a cut-out into which a connecting piece of this type is inserted. The connecting piece 13 according to the invention comprises a tubular body 18 that is made of an electrically conductive material and can be inserted into the cut-out 23 in the housing part 1A, the end pieces 19, 20 of which body are designed for the attachment of the fluid-conducting lines. The connecting piece 13 is distinguished by a terminal part 16 for attaching an electrical protective conductor or equipotential bonding system, the terminal part 16 being electrically conductively connectable or connected to the tubular body 18. The terminal part 16 allows an electrical connection cable 17 to be directly attached to a protective conductor 15 (PE conductor).