Medical guide element with diameter transition

Abstract

Improved medical guide elements for use with dilators to be inserted into an organ or body structure of a patient, such as the kidney. The guide element includes a proximal segment and a distal segment. The diameter of the distal segment is greater than the diameter of the proximal segment. The change in diameter is abrupt, providing a discrete step transition at a point along the filament which presents a proximally-facing surface on the distal segment. When the proximal segment of the guide element is fully inserted into a dilator having a distal tip adapted for insertion into a patient, the dilator distal tip firmly abuts the proximally-facing end surface of the distal segment. The relative dimensions of the dilator tip and the discrete stepped transition of the guide element provides full shielding or over shielding of the dilator tip, thereby facilitating passage of the dilator tip along the tissue track, through the puncture hole and into the orifice.

What is claimed is: 
     
         1 - 76 . (canceled) 
     
     
         77 . An apparatus for percutaneously dilating an opening in the wall of the kidney comprising, in combination:
 an elongate introducing guide element having a proximal segment and a distal segment which meet at a juncture, said proximal segment having a first outer diameter at said juncture and said distal segment having a second outer diameter at said juncture greater than said first outer diameter, thereby forming an abrupt circumferential step comprising a proximally-facing surface such that said step creates a discrete transition between said proximal segment and said distal segment,   said distal segment comprising a distal tip and an elongate portion extending from said step to said distal tip of said distal segment, said elongate portion having an outer diameter that is substantially constant over the entire length of said elongate portion and equal to said second outer diameter; and   a dilator matched to said introducing guide element having an interior bore of sufficient size to permit said dilator to slide over the entire proximal segment of said introducing guide element,   said dilator comprising a distal tip having a distally-facing annular surface with an opening into said interior bore,   said dilator distal tip having an inner diameter less than said second diameter, such that when assembled together said dilator cannot pass distally beyond said step,   said dilator distal tip having an outer diameter substantially equal to said second outer diameter, such that that when assembled together with said dilator distal tip abutting said step their respective outer diameters match one another to provide precise shielding of said dilator distal tip and a smooth transition from said introducing guide element distal segment outer diameter to said dilator distal tip outer diameter, thereby permitting said dilator distal tip to smoothly enter said opening without resistance from said wall of said blood vessel or anatomic structure.   
     
     
         78 . The apparatus of  claim 77  wherein the wall of the kidney is the renal pelvis. 
     
     
         79 . The apparatus of  claim 78  wherein said opening to said wall of said renal pelvis provides entry to the renal collecting system. 
     
     
         80 . In a method for percutaneously creating and dilating an opening in the wall of the kidney, wherein a pointed hollow tubular device is used to create an opening into said wall, a guide element is inserted through said tubular device into said opening, said tubular device is removed over said guide element, and a dilating catheter is advanced over said guide element to dilate said opening, the improvement comprising:
 deploying a guide element having a proximal segment and a distal segment which meet at a juncture, said proximal segment having a first outer diameter at said juncture and said distal segment having a second outer diameter at said juncture greater than said first outer diameter, thereby forming an abrupt, circumferential step comprising a proximally facing surface, such that said circumferential step creates a discrete transition between said proximal segment and said distal segment, wherein said circumferential step is positioned outside said wall as said tubular device is removed; and   advancing said dilating catheter distally along said proximal segment of said guide element until the distal tip of said dilating catheter abuts said circumferential step.   
     
     
         81 . The apparatus of  claim 80  wherein the wall of the kidney is the renal pelvis. 
     
     
         82 . The apparatus of  claim 81  wherein said opening to said wall of said renal pelvis provides entry to the renal collecting system.