Mesenteric Abscess Complicated by Septic Peritonitis in a Dog: Multimodal Diagnosis, Surgical Management, and Serial Quantitative Bacterial Load Monitoring

Mesenteric abscesses are an uncommon cause of septic peritonitis in dogs, and serial quantitative monitoring of bacterial load in peritoneal exudate has rarely been reported. This case report describes the diagnostic work-up and treatment response of a 14-month-old, 33 kg intact male Cane Corso with a mesenteric abscess complicated by septic peritonitis, two weeks after treatment for babesiosis. The dog presented with a 72 h history of anorexia, vomiting, and abdominal pain. Abdominal radiography revealed decreased peritoneal serosal contrast and findings suggestive of foreign material ingestion. Serial ultrasonography identified a mesenteric abscess with peritoneal effusion. Exploratory laparotomy confirmed the diagnosis; the abscess was excised, and the abdominal lavage was performed. Histopathology confirmed a mesenteric abscess with marked neutrophilic infiltration. Bacterial culture isolated Escherichia coli and Enterococcus faecium, with antimicrobial therapy guided by susceptibility testing. Serial quantitative bacterial counts of the peritoneal exudate on three postoperative occasions showed a progressive decline, paralleling clinical and hematological improvement. The dog fully recovered, with complete clinical and laboratory normalization confirmed at the 60-day reassessment. This case suggests that a multimodal diagnostic approach may assist in guiding management and confirming treatment response in canine mesenteric abscess with septic peritonitis, although the role of serial quantitative monitoring requires further evaluation.