AIM To assess the insulating effect of a poloxamer 407(P407)-based gel during microwave ablation of liver adjacent to the diaphragm.METHODS We prepared serial dilutions of P407, and 22.5%(w/w) concentration was identified as suitable for ablation procedures. Subsequently, microwave ablations were performed on the livers of 24 rabbits(gel, saline, control groups, n = 8 in each). The P407 solution and 0.9% normal saline were injected into the potential space between the diaphragm and liver in experimental groups. No barriers were applied to the controls. After microwave ablations, the frequency, size and degree of thermal injury were compared histologically among the three groups. Subsequently, another 8 rabbits were injected with the P407 solution and microwave ablation was performed. The levels of alanine aminotransferase(ALT), aspartate aminotransferase(AST), blood urea nitrogen(BUN) and creatinine(Cr) in serum were tested at 1 d before microwave ablation and 3 and 7 d after operation. RESULTS In vivo ablation thermal injury to the adjacent diaphragm was evaluated in the control, saline and 22.5% P407 gel groups(P = 0.001-0.040). However, there was no significant difference in the volume of ablation zone among the three groups(P > 0.05). Moreover, there were no statistical differences among the preoperative and postoperative gel groups according to the levels of ALT, AST, BUN and Cr in serum(all P > 0.05).CONCLUSION Twenty-two point five percent P407 gel could be a more effective choice during microwave ablation of hepatic tumors adjacent to the diaphragm. Further studies for clinical translation are warranted. AIM To assess the insulating effect of a poloxamer 407 (P407) -based gel during microwave ablation of liver adjacent to the diaphragm. METHODS We prepared serial dilutions of P407, and 22.5% (w / w) concentration was identified as suitable for ablation procedures The P407 solution and 0.9% normal saline were injected into the potential space between the diaphragm and liver in experimental groups (gel, saline, control groups, n = 8 in each) . No barriers were applied to the controls. After microwave ablations, the frequency, size and degree of thermal injury were compared histologically among the three groups. alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN) and creatinine (Cr) in serum were tested at 1 d before microwave ablation and 3 and 7 d after operation RESULTS In vivo ablation thermal injury to the adjacent diaphragm was evaluated in the control, saline and 22.5% P407 gel groups (P = 0.001-0.040). However, there was no significant difference in the volume of ablation zone among the three groups ( P> 0.05). Moreover, there were no statistical differences among the preoperative and postoperative gel groups according to the levels of ALT, AST, BUN and Cr in serum (all P> 0.05) .CONCLUSION Twenty-two point five percent P407 gel be a more effective choice during microwave ablation of hepatic tumors adjacent to the diaphragm. Further studies for clinical translation are warranted.