Colectomy (col- + -ectomy) is the surgical removal of any extent of the colon, the longest portion of the large bowel. Colectomy may be performed for prophylactic, curative, or palliative reasons. Indications include cancer, infection, infarction, perforation, and impaired function of the colon. Colectomy may be performed open, laparoscopically, or robotically. Following removal of the bowel segment, the surgeon may restore continuity of the bowel or create a colostomy. Partial or subtotal colectomy refers to removing a portion of the colon, while total colectomy involves the removal of the entire colon. Complications of colectomy include anastomotic leak, bleeding, infection, and damage to surrounding structures.

Common indications for colectomy include:

Before surgery, patients typically undergo preoperative bloodwork, including a complete blood count and type and screen of blood type. Diagnostic imaging may include colonoscopy or CT scans of the abdomen and pelvis. In cancer patients, lesions are commonly tattooed via colonoscopy before colectomy to give the surgeon an intraoperative visual guide. For non-emergent procedures, patients are typically instructed to follow a clear liquid diet or fast and take a mechanical bowel preparation (oral osmotic agents or laxative) to clear the bowels before surgery. Antibiotics may also be prescribed ahead of surgery to reduce risk of post-operative infection.

Traditionally, colectomy is performed via an abdominal incision, a technique known as laparotomy. Minimally invasive colectomy using laparoscopy is a well-established procedure in many medical centers. Robot-assisted colectomy is growing in scope of indications and popularity.

As of 2012, more than 40% of colon resections in the United States are performed via a laparoscopic approach. For laparoscopic colectomy, the typical operative technique involves 4-5 separate incisions made in the abdomen. Trochars are introduced to gain access to the peritoneal cavity and serve as ports for the laparoscopic camera and other instruments. Studies have proven the feasibility of single port access colectomy, which would require only one small incision, but no clear benefit in terms of outcome or complication rate has been demonstrated.

Before removal, the portion of the bowel to be resected must be freed or mobilized. This is done by dissection and removal of the mesentery and other peritoneal attachments. Resection of any part of the colon entails mobilization and the cutting and sealing, or ligation, of the blood vessels supplying the portion of the colon to be removed. A stapler is typically used to cut across the colon to prevent spillage of intestinal contents into the peritoneal cavity. Colectomy as treatment for colorectal cancer also includes lymphadenectomy, or removal of surrounding lymph nodes, which may be done for staging of the cancer or removal of cancerous nodes. More extensive lymphadenectomy is sometimes accomplished by the removal of the mesocolon, the fatty tissue adjacent to the colon, which contains blood supply, lymphatics, and nerves to the colon.

When the resection is complete, the surgeon has the option of reconnecting the bowel by stitching or stapling together the cut ends of the bowel (primary anastomosis) or performing a colostomy to create a stoma, an opening of the bowel to the abdominal wall that provides an alternate exit for the contents of the gastrointestinal tract. When colectomy is performed as part of damage control surgery in life-threatening trauma resulting in destructive colon injury, the surgeon may opt to leave the cut ends of the bowel sealed and disconnected for a short time to allow for further resuscitation of the patient before returning to the operating room for definitive repair (anastomosis or colostomy).

In modern times, surgical staplers are typically used to create colorectal anastomoses, although hand sewn, or sutured, anastomoses are still done today. Studies have shown that differences in rates of anastomotic leak and surgical site contamination for stapled vs. sutured anastomoses are not statistically significant. The increased speed and decreased human variability afforded by stapling make it an attractive option for most surgeons.