Drain Fluid Amylase and pH Flag Anastomotic Leaks Early

Drain fluid biomarkers, especially amylase and pH, detect anastomotic leaks more accurately than inflammatory markers such as C-reactive protein.

• In colorectal surgery, drain amylase showed 99.6% sensitivity and 98.5% specificity, with an area under the curve of 0.93.
• Low drain pH had a pooled sensitivity of 88.1% and specificity of 94.1%.
• In upper GI surgery, drain amylase was less sensitive, at 77.3%, but specificity reached 96.0%.

Drain fluid testing may help with postoperative surveillance in selected high-risk patients. It is not yet a substitute for clinical judgment or imaging, and the upper GI results are weaker than the colorectal ones.