Drug Delivery in Interventional Nephrology

Interventional nephrology is steadily growing in the region as the incidence and prevalence of renal diseases and renal failure increase. Highlighted below are 2 areas of interest where innovation could contribute to reducing complications and improving outcomes.

PERCUTANEOUS RENAL BIOPSY

Ultrasound-guided renal biopsy is a commonly performed procedure needed to acquire renal tissue to obtain an accurate histological diagnosis of underlying renal diseases. Although major complications are uncommon, there is still the risk of excessive bleeding post-biopsy that may require blood transfusions or embolization in less than 1% of cases. In patients with higher bleeding risk, there may be a role in being able to administer a hemostatic agent in the tract of the biopsy needle to reduce the chances of bleeding immediately postprocedure. The key to its effectiveness will be the ability to deliver the agent in the exact tissue extraction site to ‘plug the hole’ made by the biopsy needle. Given that most nephrologists use a percutaneous biopsy device for the procedure, the entry tract is not always the same for each pass. Thus, the challenge would be to devise a way to accurately administer the hemostatic agent immediately post firing the renal biopsy device.

VASCULAR DIALYSIS ACCESS – ARTERIOVENOUS FISTULA AND GRAFTS

The arteriovenous fistula or arteriovenous graft (AVF/AVG) is quintessentially a lifeline of a patient undergoing long-term hemodialysis. Efforts to create and maintain patency of access have been the focus of many studies and expert discussions at conferences worldwide. Technology and pharmaceutical investment have made significant contributions to improving the life span of AVF/AVGs, from advances in plain balloon angioplasty to drug-coated balloon angioplasty and more recently drug-coated stents.

Recent research has clearly cemented the use of drugcoated balloons to improve access outcomes in selected patients. They have been shown to reduce the frequency of repeat interventions required and extend the longevity of the access. Balloons coated with an immunosuppressive agent such as paclitaxel or sirolimus are inflated across the target lesion, achieving contact with the endovascular surface and hence embedded into the affected endothelium. This, in turn, reduces the development of neo-intimal hyperplasia (NIH) for recurring stenosis in the AVF. Conceptually it is a rather elegant solution to be able to administer the drug to a localized endovascular lesion.

Endovascular stents are also used in vascular dialysis access and can be useful in situations where there is significant recoil post-angioplasty.

This consists of bare metal stents, covered stents or stentgrafts, and drug-coated stents. Bare metal stents are largely now less favored than covered stent grafts for AVF/AVGs due to the higher occurrence of restenosis from NIH across the stent struts. Recently, drug-coated stents are being explored as a possible alternative to further reduce NIH into the stent lumen.

Novel ways of targeted drug delivery in interventional procedures are still evolving and it is exciting to see what the future holds especially in the realm of nanotechnology in this clinical area.