This paper consists of the design and construction of an intraoperative peritoneal lavage device. It is intended for cleaning the intra-abdominal cavity during a surgical procedure, once the etiology of a peritonitis has been identified and treated. Its purpose is to improve the current standard treatment consisting of simple pouring saline solution. A good washing procedure aids stopping the inflammatory and infectious process generated after the contamination due to the perforation of a hollow viscera. COMSOL Multiphysics software was used to simulate the biomechanical behavior of the liver against localized pressure. A graphical interface allows the user to predict liver deformation under different fluid pressures and positions simulating the lavage procedure. A preliminary prototype was implemented and a clinical trial was approved in an animal model. Three intraperitoneal structures belonging to a sheep were analyzed to observe the effect of the lavage. In closing, the final prototype implemented delivers a maximum force of 0.08 [N] and a pressure of 25.6 [kPa], and complied with the specialist's expectations.