+ Factors related to the change of Na + blood and the risk of causing hyponatremia after surgery below the normal level (<135 mmol / l) in the 3% group of sorbitol are peritoneal perforation, surgery time ≥60 minutes, gland weight ≥60g, cutting weight ≥40g, irrigating solution absorption volume ≥1000ml and irrigating solution volume use ≥30 liters.