Long-Term Evaluation of Biodegradable Hydrogels as an Effective Means of Tissue Closure After Laparoscopic Porcine Partial Nephrectomy

Sanjay Ramakumar, MD
Section of Urology

In urology, a partial nephrectomy (removal of part of a kidney) is performed for a kidney cancer in patients in whom a total nephrectomy would result in dialysis. Since 1992, kidneys have been removed using minimally invasive surgical techniques, namely laparoscopy, instead of large incisions. The advantage of this approach is not only in money saved resulting from a decreased stay in the hospital, but also more rapid healing for the patient and return to normal life. Ultimately in the near future, most surgeries will be carried out by laparoscopic techniques. However, cutting across the kidney results in severe bleeding that must be controlled. Now that more laparoscopic partial nephrectomies are being performed than ever, finding ways to stop bleeding (hemostasis) during laparoscopic surgery, when the hole through which the surgery is being performed is too small for the surgeon's hand to hold pressure, is increasingly important. Traditional hemostatic methods (electrocautery, argon laser coagulation, fibrin glue, etc.) are not always effective. We believe that the answer to this problem is a new method of hemostasis using tissue sealants. Specifically, biodegradable hydrogel polymers, which have already received FDA approval for lung use, can be applied to the raw surface of the kidney and seal all of the blood vessels as well as the open urinary collecting system. In a preliminary study, we have used these hydrogels on the kidneys of pigs on which laparoscopic partial nephrectomies were performed. When applied laparoscopically, a physical bond was formed that immediately stopped bleeding from the cut surface of the kidney.

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In order to test the durability and evaluate the effect of the hydrogel on the underlying kidney and surrounding organs, a long-term survival study is planned. Specifically, the objectives of the study are:

1. Creation of a survival laparoscopic hydrogel/partial nephrectomy model in the pig
2. Evaluate the capability of the hydrogel to withstand pressure by performing an in vivo monitored pressure experiment and compare with standard techniques and currently available hemostatic products
3. Test the long-term effectiveness (i.e. delayed bleeding, urine leak, etc.) of the hydrogel with evaluations at specific endpoints in time
4. Evaluate the hydrogel's effect on surrounding organs (i.e. adhesions to bowel or adjacent organs)
5. Evaluate the histological effect of the hydrogel on the underlying healing kidney and surrounding structures as well as the pigs immunological response during and after the polymer degrades

We expect this surgical model can be performed safely and reliably and that delayed complications should not occur. We also plan to investigate the biological response of the kidney to the hydrogel with inflammatory cells as well as other tissue response mechanisms such as angiogenesis (formation of new blood vessels). This study has applications not only in urology, but in all organ systems and could dramatically alter the way surgeons treat and prevent blood loss during surgery.

For more information on this study, please contact:

Sanjay Ramakumar, MD
Arizona Health Sciences Center
Department of Surgery
1501 N. Campbell Avenue, Rm. 4409
PO Box 245077
Tucson, AZ 85724-5077

Email: sramakum@email.arizona.edu