**Abstract**

Colorectal anastomosis is defined as a surgical procedure in which the colon is attached to the remainder of the rectum after most or some part of it was removed during an intervention. A straight colorectal anastomosis implies a direct attachment, while a J-pouch colorectal anastomosis implies a previous creation of a reservoir, or "pouch" out of bowel material. The problem of colorectal anastomosis safety and outcome is among the most important and persistent issues in colorectal surgery, mainly due to the anastomotic leakage, a threatening and dangerous complication, with an incidence of up to 20% or even more in case of surgical oncology. Various prediction models and anastomosis testing techniques have been described in order to prevent or identify early any possible imperfection of the anastomosis, each with pros and cons. The measures generally used to increase the safety and reliability of the colorectal anastomosis are to evaluate the blood supply of the tissues anastomosed with indocyanine green, or to test the mechanical integrity of the anastomosis for leakage by employing air, methylene blue, or tension.

**Keywords:** colonic fistula, anastomotic leakage, colorectal anastomosis, colorectal surgery complications, total mesorectal excision (TME)

### **1. Introduction**

An anastomosis is a surgical connection between two structures. It usually means a connection that is created between tubular structures, such as blood vessels or loops of the intestine. Surgeons can choose to join together the two parts of the intestine by using either sewing (sutures) or staples. Sewing by hand has been used successfully for over 100 years. However, stapling takes less time to perform. As with any intervention, anastomosis carries some risks. These include blood clots, bleeding, scarring, blockage, stricture, or abnormal narrowing, damage to the surrounding structures, and infections, all of which can lead to anastomotic leakage, sepsis, septic shock, or even death (**Figures 1** and **2**).
