What is the diagnostic peritoneal fluid to serum creatinine ratio that indicates uroabdomen?

• A. Greater than 2:1
• B. 1:1
• C. Less than 1:1
• D. Greater than 3:1

Answer: (A)

The test hinges on how creatinine distributes when urine leaks into the peritoneal cavity. In uroabdomen, the peritoneal fluid becomes urine-like with a high creatinine level, while serum creatinine is elevated but not as high. So the ratio of peritoneal fluid creatinine to serum creatinine becomes markedly greater than 1, typically greater than 2:1. This >2:1 ratio is a strong clue that urine is present in the peritoneal cavity.

If there’s no uroabdomen, peritoneal fluid creatinine mirrors serum creatinine, giving about a 1:1 ratio. A ratio well above 2:1 supports uroabdomen, whereas ratios around 1:1 or lower argue against it.