A ratchet wrench for use in connection with medical instruments comprises a handle and a drive element which is rotatable around an axis (M) with respect to the handle. The wrench is adapted to tighten or loosen a respective element and a ratchet mechanism which is in connection with the drive element and which permits movement with respect to the handle in a first direction of rotation (R1) and blocks movement in the other direction of rotation (R2). The handle comprises a flat arm, wherein the ratchet mechanism is arranged on a bearing surface of the flat arm, and wherein the drive element extends through an opening in the flat arm in which opening the drive element is rotatably arranged.