BACKGROUND Obesity is a pandemic that is currently uncontrolled. In the surgical population, bariatric surgery is a sustainable and attractive option. However, both obesity and surgery can independently increase the risk for venous thromboembolism and subsequent significant and even fatal adverse effects. CASE REPORT We present the unique case of a 63-year-old woman who developed substantial venous thrombosis in the postoperative period following a laparoscopic hiatal hernia repair and Roux-en-Y gastric bypass. Venous thrombosis following surgery is a known possible complication, but we felt that this case required reporting due to the extreme extent of thrombosis and the significant course of events that occurred following her readmission. Due to the increased thrombus burden, the patient developed phlegmasia cerulea dolens and required operative thrombectomy. With restoration of blood flow following the procedure, the patient's clinical status rapidly declined, likely due to reperfusion injury. Ultimately, she developed multisystem organ failure, which included the constellation of shock, hypoxic respiratory failure, acute renal failure, shock liver, and, finally, cardiopulmonary arrest. CONCLUSIONS As the authors of this paper, we were especially inclined to report this particular case as the patient's clinical course was exceedingly complex due to her presenting phlegmasia cerulea dolens. The course was further complicated postoperatively by the detrimental sequelae of massive reperfusion injury, which likely eventually led to her death. We felt this pertinent to present because, after an extensive PubMed literature review, this sequence of events following gastric bypass surgery has yet to be reported in the literature.