Serial Evaluation of Abdominal Fluid and Serum Amino‐terminal pro‐C‐type Natriuretic Peptide in Dogs with Septic Peritonitis

BACKGROUND: Serum N‐terminal pro‐C‐natriuretic peptide (NT‐proCNP) has shown promise as a diagnostic biomarker for sepsis. Its sensitivity to detect dogs with septic peritonitis (SP) is reportedly low, perhaps attributable to the compartmentalization of NT‐proCNP in the abdominal cavity. OBJECTIVES: To evaluate the use of an ELISA for the measurement of NT‐proCNP in canine abdominal fluid and to describe the peri‐operative pattern of abdominal fluid and serum NT‐proCNP concentrations in dogs with SP. ANIMALS: Five client‐owned dogs with nonseptic abdominal effusion of varying etiologies and 12 client‐owned dogs with SP undergoing abdominal surgery and placement of a closed‐suction abdominal drain (CSAD). Six dogs were included upon hospital admission; 6 were included the day after surgery. METHODS: Prospective pilot study. A commercially available ELISA kit was analytically validated for use on canine abdominal fluid. The NT‐proCNP concentrations were measured in the abdominal fluid of control dogs, and in serum and abdominal fluid of dogs with SP from admission for CSAD removal. RESULTS: In dogs with SP, admission abdominal fluid NT‐proCNP concentrations were lower than the concurrent serum concentrations (P = 0.031), and lower than control canine abdominal fluid concentrations (P = 0.015). Postoperatively, abdominal fluid NT‐proCNP concentrations remained lower than serum concentrations (P < 0.050), except on day 4. CONCLUSIONS AND CLINICAL IMPORTANCE: The ELISA kit was able to measure NT‐proCNP in canine abdominal fluid. In dogs with SP, low serum NT‐proCNP concentrations cannot be explained by abdominal compartmentalization.