Table 2.

Study characteristics of animal studies in relation to anastomotic leakage

Author	Year	Level of evidence	Operations	Definition of anastomotic leakage	Method of measurement	Time of measurement	Main results
MMP-9 in relation to AL
Shogan	2015	5	Distal colon segment resection	Visible dense adhesions to the anastomotic line indicating inflammation; a hard, grossly inflamed and non-compressible anastomosis; grossly disrupted anastomotic site with adjacent purulent like material or a grossly visible hole and ulceration and disruption on the luminal mucosal side.	Zymography and Western blot	POD 6	1. Significantly higher MMP-9 activity in rats with anastomotic leakage 2. MMP-9 inhibition results in lower leakage rates
MMP-9 at different sites around anastomosis
Ågren	2006	5	Distal colon segment resection	Not applicable	Immunohistochemistry	Day 0, POD 3 or 7	1. No MMP-9 activity on day 0. 2. More MMP-9 positive cells in the anastomotis area compared with uninjured areas. 3. Higher MMP-9 levels directly around the sutures compared with suture-free zones of the anastomotis area.
De Hingh	2005	5	Distal colon transection	Not applicable	Zymography	Day 0 (no intervention), POD 1 or 3	Significantly higher MMP-9 activity on POD 1 and 3 in the anastomosis area compared with uninjured intestine.
Seifert	1996	5	Distal colon segment resection	Not applicable	Zymography	Day 0, POD 1, 2, 3, 7, or 90	1. No MMP-9 activity on day 0 and POD 90 2. Higher MMP-9 activity in anastomosis area on POD 1, 2, 3, and 7 compared with uninjured areas.
Shaper	2001	5	Distal colon segment resection	Not applicable	Zymography and Immunohistochemistry	6 h after surgery or POD 7	More MMP-9 activity in anastomosis area at 6 h postoperative and on POD 7 compared with uninjured areas.

MMP-9, matrix metalloproteinase-9; POD, postoperative day