A 38-year-old female was admitted because of lymphangioleiomyomatosis (LAM)-associated massive chylous ascites and progressive cachexia. A peritoneovenous shunt (Denver^® shunt) was placed, and thereafter lymphocytopenia and malnutrition resulting from periodic peritoneocentesis were successfully ameliorated. The shunt had worked well under antiplatelet therapy (aspirin) to control chylous ascites for 52 months thereafter. However, thrombus was identified in the right brachiocephalic vein by contrast-enhanced computed tomography. Because sirolimus was demonstrated to be effective to control ascites, we decided to remove the shunt at 68 months after its placement and eliminate the further risk of developing venous thrombosis. The efficacy and safety of peritoneovenous shunt for a limited period have been well documented for intractable ascites, but the feasibility, benefit, and adverse events for a long-term placement have never been reported. To the best of our knowledge, our case for the first time demonstrated the long-term efficacy over 4 years, but venous thrombosis occurred insidiously. Anticoagulation therapy may be the better choice for the prevention of thrombosis rather than antiplatelet therapy.