Drain fluid amylase as a biomarker for the detection of anastomotic leakage after rectal resection without a diverting ileostomy

Anastomotic leak (AL) is the anathema of colorectal surgery. Early diagnosis is an essential segue to early intervention. A temporary diverting ileostomy (TDI) does not prevent an AL and presents inherent complications of its own. Numerous drain fluid biomarkers (BM) have been studied in colorectal surgery and extravasated intraluminal substances (EILS) such as amylase have shown promise. The aim of this study was to assess drain fluid amylase (DFA) as a BM of AL after minimally invasive rectal resection without a TDI.A single centre prospective cohort study performed from 2018 to 2021. The primary outcome was DFA measured daily whilst the drain was in situ. Rectal tube amylase was also measured for the first two post-operative days to quantitate the intra-luminal levels of the enzyme. DFA was compared between patients who experienced AL and those who did not.Of the 62 patients studied, six (9.7%) experienced AL. There was a statistically significant difference in DFA between patients who experienced AL (Median:1373.5 U/L; IQR: 306-7953) and patients who did not experience an AL (Median: 27.0 U/L; IQR: 16-38); p 0.0001.The measurement of drain fluid amylase is a highly sensitive BM of early clinical anastomotic leak in patients undergoing a rectal resection with an extraperitoneal anastomosis and when a TDI is not incorporated. This simple, inexpensive and non-invasive test should be considered in all patients as an adjunct to the clinical diagnosis and differentiation of AL from other postoperative complications.