BACKGROUND Autosomal dominant polycystic kidney disease (ADPKD) is the leading genetic cause of kidney failure worldwide. It is characterized by cyst formation and growth, kidney parenchymal destruction, and complications including cyst infection, nephrolithiasis, cyst rupture, and cyst hemorrhage. Cyst bleeding is typically a self-limited event. This case report describes a 60-year-old man with ADPKD admitted with retroperitoneal hemorrhage following renal cyst rupture requiring embolization of a bleeding left lumbar artery and use of tranexamic acid. CASE REPORT A 60-year-old man with ADPKD presented with altered mental status. Labs noted hemoglobin of 4.7 g/dL. Abdominal imaging revealed polycystic kidneys and large left retroperitoneal hematoma. Angiogram demonstrated active bleeding from left L3 lumbar artery which was embolized. He was admitted to intensive care unit for hemorrhagic shock requiring multiple blood transfusions. Hemoglobin continued to downtrend despite blood products with repeat imaging demonstrating expanding retroperitoneal bleed. He underwent repeat angiogram and though there was no active bleeding, prophylactic embolization of left L1, L3, L4 lumbar and left renal capsular arteries were performed. Hemoglobin stabilized for next 3 days but continued to downtrend subsequently. Oral tranexamic acid was trialed with stabilization of the hemoglobin. CONCLUSIONS Life-threatening retroperitoneal hemorrhage following cyst rupture in the absence of major trauma or use of anti-coagulants, is a rare complication in ADPKD. Treatment involves resuscitation with blood products, management of shock, and interventional radiology-guided embolization. Tranexamic acid may be considered when the above measures fail. Nephrectomy may be indicated for refractory bleeding. This report highlights the diagnosis and management of massive cyst bleeding in ADPKD.