A 77-year-old male with AML and non- ischemic cardiomyopathy presented to our hospital with one month history of dyspnea on exertion and exercise intolerance. Review of systems was remarkable for abdominal pain, poor appetite, and increased abdominal girth for two weeks. Physical examination revealed a well-nourished, elderly male with decreased breath sounds over the posterior lung bases, and periumbilical tenderness with a distinct fluid wave. Laboratory studies were significant for WBC-11.3 x103, Hgb-8.9g/dL, Plt-106 x 103, Blast %-32, BNP-275 pg/mL, AST-21 U/L, ALT-14 U/L, and an indeterminate Quantiferon gold. CT abdomen/pelvis revealed hepatosplenomegaly with engorgement of the portal vein, new onset ascites, and a peripherally enhancing pelvic fluid collection (Figure 1). A paracentesis was performed. Analysis of the ascitic fluid revealed WBC -34,850 cells/μL with 45% blasts, total protein-4g/dL, LDH- 974 U/L (serum 383 U/L), albumin 2.7 g/dL (serum, 3.6 g/dL) and adenosine deaminase 102 U/L. Cytologic examination of the fluid showed a markedly cellular fluid with high nuclear to cytoplasmic ratio, nuclear contour abnormalities, and abundant mitotic figures consistent with myeloid cells (Figure 2). No microorgamisms were identified, including mycobacterium. Flow cytometry demonstrated cells that expressed CD13, CD33, CD15, CD11b, CD11c, CD64, CD34, CD117, HLA-DR, CD71 and CD38. These findings were consistent with AML and the patient was started on Hydroxyurea and Ruxolitinib. Malignant ascites is a common complication of solid tumors, but is rarely witnessed in hematologic malignancies. In particular, leukemic ascites is an exceedingly rare phenomenon manifesting at initial presentation or late extramedullary relapse following bone marrow transplantation. There have been very few cases of leukemic ascites reported in the literature, however this is the first case of leukemic ascites with elevated adenosine deaminase levels. Although the pathophysiology in this case is not fully understood, it is speculated to be the result of leukemic infiltration of the lymphatics or peritoneal deposition of tumor cells. However infectious etiologies should be thoroughly excluded prior to making this diagnosis and planning on treatment. This report also emphasizes the importance of prompt evaluation of new onset ascites and the performance of flow cytometry and cytologic analysis especially in a patient with known history of malignancy.Figure: CT Abdomen/Pelvis Image of Peripherally Enhnacing Pelvic Fluid.Figure: Ascitic Fluid cellular fluid with myeloid cells.