Objective: To determine clinical characteristics of primary bacterial peritonitis (infection of the peritoneal cavity with no identifiable intraperitoneal source of infection) and compare characteristics of primary and secondary peritonitis in dogs and cats.
Design: Retrospective case series.
Animals: 24 (primary peritonitis) and 60 (secondary peritonitis) client-owned dogs and cats.
Procedures: Data from medical records of dogs and cats with primary and secondary peritonitis were reviewed for descriptive information regarding primary peritonitis and for comparison between the 2 forms of peritonitis.
Results: 15 dogs and 9 cats met inclusion criteria for primary peritonitis, and 49 dogs and 11 cats met inclusion criteria for secondary peritonitis. The most common historical findings in dogs and cats with primary and secondary peritonitis were lethargy, vomiting, and anorexia. Dogs with secondary peritonitis more often developed peritoneal exudates than those with primary peritonitis, and dogs with primary peritonitis were more often infected with gram-positive bacteria than those with secondary peritonitis. No difference in outcome was detected between all animals with primary versus secondary peritonitis; however, dogs with secondary peritonitis treated with surgery were more commonly discharged than those with primary peritonitis treated with surgery.
Conclusions and clinical relevance: Differences in primary and secondary peritonitis related to historical, physical examination, and clinical laboratory findings; bacteriologic findings; peritoneal effusion characteristics; and outcome were detected. However, larger case numbers are needed before alternative recommendations, such as avoidance of surgery, can be made.