S5498 Bacterial Peritonitis in a Patient With Malignant Ascites From Breast Cancer

Introduction: Malignancy-related ascites (MRA) is a complication of metastatic disease that is associated with a high healthcare burden, reduced quality of life, and poor prognosis. Bacterial peritonitis (BP) is a potential complication in all patients with ascites but is more common in patients with end stage liver disease (ESLD). We describe a case of BP in a patient with MRA and breast cancer. Case Description/Methods: A 62-year-old woman with a history of breast cancer, diagnosed 2 years prior, and liver metastases presented with right-sided abdominal pain. Non-contrast computed tomography (CT) scan showed mesenteric volvulus and new onset, small volume ascites. Diagnostic paracentesis (DP) revealed serum ascites albumin gradient <1.1 g/dL and total protein >2.5 g/dL, suggestive of a non-portal hypertensive etiology. The cell count revealed 6.9k RBCs, 972 WBCs, and 64% PMNs, consistent with BP. Cytology was positive for malignant cells from the breast. Body fluid culture did not speciate an organism. The patient was started on ceftriaxone and albumin. Repeat DP was completed 4 days later. Cell count showed 6.8k RBCs, 648 WBCs, and 40% PMNs. The patient completed 7-days of ceftriaxone and was discharged on ciprofloxacin and diuretics. In the following 6 weeks, the patient was hospitalized twice with recurrence of ascites. Repeat paracenteses did not reveal recurrence of BP. The patient transitioned to hospice and died within 3 months from the initial paracentesis. Discussion: MRA accounts for 7%-10% of all ascites cases. Existing research into the topic has primarily focused on management of recurrent ascites and reducing symptom burden. Few case reports of BP in MRA in exist, and there is little research on the prevalence of BP in this population. One 2024 study identified the 1-year prevalence rate of BP in patients with GI cancers to be 14%, although most cases were secondary BP. In comparison, the estimated prevalence of spontaneous BP in cirrhosis is 10-30%. The etiology of BP in our patient is unclear. Secondary BP is possible in the setting of mesenteric volvulus, but spontaneous BP cannot be ruled out. Current society guidelines recommend DP in the setting of new onset ascites and in patients with ESLD and decompensation requiring hospital admission. However, there are no specific recommendations for DP in patients with malignant ascites. Despite the poor prognosis of MRA, BP remains a treatable complication that may be currently underrecognized. Further study into the prevalence of BP in MRA is warranted.