Stencil-Based Preoperative Mapping
Marking stencils are provided by some dialysis catheter manufacturers for the most commonly used catheter designs. Properly constructed stencils contain critical catheter design information, including the distance between the deep cuff and the coil, suggested subcutaneous tunnel configurations, and recommended exit-site locations relative to the position of the superficial cuff. Additional features of a well-designed stencil plate permit its precise orientation on the trunk region according to fixed anatomical landmarks, such as the upper edge of the pubic symphysis, representing the anterior upper border of the true pelvis, and the anatomical midline of the torso. Stencils permit accurate and reproducible association of the catheter design elements to these anatomical landmarks to help determine the best catheter style and insertion site that will produce optimal pelvic position of the catheter coil and ideal exit-site location. In addition to the preoperative evaluation, the marking stencil is used again at the time of the catheter placement procedure to retrace the previously determined insertion incision, tunnel configuration, and exitsite location.6
Figure 3A. Mapping using stencil for Tenckhoff catheters with straight and swan neck intercuff segments. With supine patient, align medial border of stencil with midline of abdomen and stencil reference line for pubis with the upper border of the pubic symphysis. Mark exit-sites for both catheter configurations. Figure 3B. On day of procedure, mark cutouts for the insertion incision, tunnel configuration, cuff positions, and exit-site location for selected catheter. It is sufficient to mark only the exit-site cutout during preoperative assessment to select catheter type.
Figure 3 demonstrates use of a marking stencil to determine insertion site, tunnel track configuration, and exit-site location for Tenckhoff-style catheters with a straight and preformed swan neck bend in the intercuff tubing segment. With the patient supine, the reference point toward the lower border of the stencil is aligned with the upper border of the pubic symphysis and the medial border of the stencil with the midline of the abdomen (Figure 3A). During preoperative assessment for catheter selection, it is sufficient to only mark the prospective exit-site. At the time of the catheter insertion procedure, the insertion site, tunnel track, and exit-site cutouts on the stencil are marked (Figure 3B).