An intravascular catheter for performing dialysis, comprising: a distal end for insertion; a proximal end; and an arterial lumen (2, 22) and a venous lumen (3, 20) extending therebetween; the distal end for insertion: terminating with a tip; at least one distally facing opening in fluid communication with the arterial lumen of the catheter, at least one distally facing opening in fluid communication with the venous lumen of the catheter, one or more proximal side facing openings (11, 23) in fluid communication with the arterial lumen of the catheter, and one or more proximal side facing openings (11, 26) in the venous lumen of the catheter, wherein the side facing openings include a proximal-most side facing opening (4, 11, 25), wherein the proximal-most side facing opening is located proximal to the distal facing openings in the catheter and is the proximal-most side facing opening in the entire distal end of the catheter; and characterized in that a radiopaque marker (5, 12, 24) is positioned proximally adjacent to or at the proximal-most side facing opening and radiographically distinguishes the location of the radiopaque marker proximally adjacent to or at the proximal-most side facing opening from the rest of the distal end, and wherein no side facing opening other than the side facing opening associated with the radiopaque marker proximally adjacent to or at the proximal-most side facing opening is radiographically distinguishable from the rest of the distal end, and wherein the distance between the tip and the radiopaque marker defines a functional catheter length in the range of about 1.5 cm to about 5 cm. a distal end for insertion; a proximal end; and an arterial lumen (2, 22) and a venous lumen (3, 20) extending therebetween; the distal end for insertion: terminating with a tip; at least one distally facing opening in fluid communication with the arterial lumen of the catheter, at least one distally facing opening in fluid communication with the venous lumen of the catheter, one or more proximal side facing openings (11, 23) in fluid communication with the arterial lumen of the catheter, and one or more proximal side facing openings (11, 26) in the venous lumen of the catheter, wherein the side facing openings include a proximal-most side facing opening (4, 11, 25), wherein the proximal-most side facing opening is located proximal to the distal facing openings in the catheter and is the proximal-most side facing opening in the entire distal end of the catheter; and characterized in that a radiopaque marker (5, 12, 24) is positioned proximally adjacent to or at the proximal-most side facing opening and radiographically distinguishes the location of the radiopaque marker proximally adjacent to or at the proximal-most side facing opening from the rest of the distal end, and wherein no side facing opening other than the side facing opening associated with the radiopaque marker proximally adjacent to or at the proximal-most side facing opening is radiographically distinguishable from the rest of the distal end, and wherein the distance between the tip and the radiopaque marker defines a functional catheter length in the range of about 1.5 cm to about 5 cm. terminating with a tip; at least one distally facing opening in fluid communication with the arterial lumen of the catheter, at least one distally facing opening in fluid communication with the venous lumen of the catheter, one or more proximal side facing openings (11, 23) in fluid communication with the arterial lumen of the catheter, and one or more proximal side facing openings (11, 26) in the venous lumen of the catheter, wherein the side facing openings include a proximal-most side facing opening (4, 11, 25), wherein the proximal-most side facing opening is located proximal to the distal facing openings in the catheter and is the proximal-most side facing opening in the entire distal end of the catheter; and characterized in that a radiopaque marker (5, 12, 24) is positioned proximally adjacent to or at the proximal-most side facing opening and radiographically distinguishes the location of the radiopaque marker proximally adjacent to or at the proximal-most side facing opening from the rest of the distal end, and wherein no side facing opening other than the side facing opening associated with the radiopaque marker proximally adjacent to or at the proximal-most side facing opening is radiographically distinguishable from the rest of the distal end, and wherein the distance between the tip and the radiopaque marker defines a functional catheter length in the range of about 1.5 cm to about 5 cm.