Dialysis catheters with optimized user-friendly connections

A catheter is provided which has been optimized so as to become mistake-proof, user-friendly, and manually connectable to a transfer device by which the patient may hook up the catheter to a source of dialysis fluid. The catheter of the invention preferably has an outer segment which is softer than the harder internal segment and affords greater comfort to the patient. In addition, the catheter has an enlarged outer portion to lower interference and allow the catheter to be manually connected to a suitable connection device, and contains overmolded segments that can have different diameters and cross-sections so that the catheter may be optimized to meet differing requirements in any specific peritoneal dialysis operation while maintaining the integrity and structure of a non-segmented catheter. The catheter can also be made with at least two lumens wherein the lumens have a unique geometric shape so as to fit in lock-and-key fashion to suitable connection devices.