Combined acute lung injury (ALI) and kidney injury (AKI) is a common problem in critically ill patients. By combining pulmonary (gas exchange) and renal (hemofiltration) support in one extracorporeal device with low-flow resistance, we seek to provide less artificial surfaces maintaining sufficient organ support. Modified Interventional Lung Assist (iLA) Membrane Ventilator (miLA), consisting of polymethylpentene gas exchange membranes and polyethersulfone hemofiltration membranes, was compared in vitro with the original iLA design, consisting only of gas exchange membranes, regarding both delivery volume and loss in pressure versus pump rate. Efficiency tests concerning gas exchange and hemofiltration rate were performed in vitro and in vivo. In vitro analyses showed no differences between both systems, with adequate filtration rates in miLA. Anticoagulation and constant blood pressure allowed 1.2 L/min of blood flow and hemofiltration rates of 70 ml/h through miLA in vivo. No major differences between concentrations of filtered molecules in blood and hemofiltrate were found. A stable gas exchange function was maintained. No signs of hemolysis were detected. Our results confirm the feasibility of single-device support for combined pulmonary and renal injury. Novel devices expanding on this concept may potentially improve therapy of critically ill patients with ALI/AKI.