A dialysis catheter (10) includes a first portion (35) having an outer wall having a first diameter, an elongated distal portion (31) having a second diameter smaller than the first diameter, and a transition region (47) between the first portion and distal portion. A first longitudinally extending venous lumen (40) is configured to deliver blood. First and second independent longitudinally extending arterial lumens (50, 60) are configured to withdraw blood from a patient. The venous lumen (40) and first arterial lumen (50) have first and second regions (13a, 13b, 17a, 17b) each positioned a first distance from the outer wall of the catheter and a third region (13c, 17c) positioned a second shorter distance from the outer wall of the catheter to form an arch shaped wall portion (13, 17) progressively increasing in thickness from the third region toward the first region and from the third region to the second region.
