**4.3 Exchange of PF stent**

Stents are changed routinely at 12 months (although licensed for 3 months), using the following technique:

A clip is used to identify a suitable position to incise the skin anteriorly, ideally half way along the stent but any position proximal to the bladder is acceptable. It is better to be able to see this site and the proximal coil in the kidney in the same fluoroscopic image. Making a small transverse incision at the appropriate site exposes the stent. The stent is then cut and a Sensor guide-wire passed through the proximal portion of the stent, which is then removed. The new stent is passed over the guide-wire before withdrawing the wire. The guide-wire is then passed into the bladder via the distal end of the old stent, which is then removed. The distal end of the new stent is passed over the wire into the bladder and the guide-wire removed endoscopically from the distal end of the stent (Minhas et al., 1999).

Extra-Anatomic Urinary Drainage for Urinary Obstruction 289

transverse incision is required. Insertion of the permanent Detour stent follows the same principals described above but because it is a bigger stent (29F), it requires the tract to be dilated to 30F (Lloyd et al., 2007). This is achieved with a 30F renal Amplatz sheath and a large-bore plastic subcutaneous tunneling device, which are included in the kit (Fig. 8a-f). A lower abdominal transverse incision is undertaken before a 1cm open cystostomy is performed via which the stent is placed into the bladder and secured with 4-0 Vicryl sutures to the bladder serosa. The large bore subcutaneous stent can be easily palpated and seen in

Fig. 8a. Lateral percutaneous track using the existing nephrostomy to inject contrast to

Fig. 8b. Insertion of the proximal end of the Detour stent through the Amplatz sheath into

the kidney (note yellow radiolucent ring to aid positioning).

outline and dilate the pelvi-calyceal system

the thin patient (Fig. 9).

Fig. 6. Supra-pubic puncture and peel-away sheath used to deliver stent into the bladder under cystoscopic control.

Fig. 7. Wounds closed with subcutaneous absorbable sutures and skin glue.
