Investigation of Forces Involved in Closure of the Renal Remnant After Simulated Partial Nephrectomy

Objective To investigate the potential biomechanical causes of the complications of partial nephrectomy (PN) in a preclinical model of sliding-clip renorrhaphy. PN is a reference standard for amenable small renal masses. One disadvantage of PN, however, is the risk of postoperative bleeding and/or urinary leak. Materials and Methods Simulated tumor excision and reconstruction using sliding-clip renorrhaphy were performed on fresh porcine kidneys. Suture tension (newtons, N) was measured in nonperfused and perfused states. Results Mean suture tension initially applied during renorrhaphy was 2.8 ± 0.7 N. After simulated perfusion to 120 mm Hg, increased tension was necessary to control fluid extravasation (average, 3.2 ± 0.7 N). For intravascular pressures above 200 mm Hg, an average tension of 3.4 ± 0.7 N was necessary to prevent observable leakage. The increase in suture tension under normal and hypertensive states averaged 21 ± 28% and 29 ± 31%, respectively. In experiments examining maximum suture tension before suture tear through, failure of the anchored sutures varied with the width of incorporated renal capsule. Mean forces were 5.7 ± 3.2, 8.8 ± 5.7, and 14.0 ± 6.0 N with 0.5, 1.0, and 1.5 cm of capsule, respectively. Review of video footage indicated that acute angles appear to contribute to suture failure. Conclusion This study demonstrates that the tension required to cause suture failure is only slightly higher than the tension typically applied during PN and necessary to control bleeding and urine leaks. After reperfusion of the kidney, the tension can increase by ≥29% under hypertensive conditions. Incorporation of sufficient (≥0.5 cm) capsule and avoidance of acute angles of entry or exit during closure of the kidney are likely to reduce suture failure.