Acute Peritonitis: A Mimic of Malignancy-Related Ascites in a Patient With Peritoneal Carcinomatosis.

Peritonitis, an inflammation of the peritoneal cavity, can be caused by various factors. The presence of ascites in a cancer patient is concerning for either metastasis or advanced cancer. Diagnosing acute peritonitis in a patient with cancer-related ascites can be quite challenging and often requires additional diagnostic procedures, such as paracentesis, to confirm the diagnosis and identify the exact cause of the ascites. Even with paracentesis, determining the exact cause of ascites can be a diagnostic challenge. Peritoneal carcinomatosis, with a poor survival rate, can originate from the peritoneal lining itself or result from intra-abdominal cancer, and trying to determine its origin can be difficult. We present the case of a 68-year-old female patient with a known history of cancer experiencing worsening ascites and peritonitis.