Micrograph of pseudomembranous colitis, an indication for colectomy. H&E stain.
Some of the most common indications for colectomy are:
- Colon cancer.
- Diverticulitis and diverticular disease of the large intestine.
- Inflammatory bowel disease such as ulcerative colitis or Crohn's disease.
- Prophylactic colectomy can be indicated in some forms of polyposis, Lynch syndrome and certain cases of inflammatory bowel disease because of high risk for development of colorectal cancer.
- Bowel infarction
Basic principles 
Traditionally, colectomy is performed via an abdominal incision (laparotomy), though minimally invasive colectomy, by means of laparoscopy, is growing both in scope of indications and popularity, and is a well-established procedure as of 2006[update] in many medical centers. Recent experience has shown the feasibility of single port access colectomy,
Resection of any part of the colon entails mobilization and ligation of the corresponding blood vessels. Lymphadenectomy is usually performed through excision of the fatty tissue adjacent to these vessels (mesocolon), in operations for colon cancer.
When the resection is complete, the surgeon has the option of immediately restoring the bowel, by stitching or stapling together both the cut ends (primary anastomosis), or creating a colostomy. Several factors are taken into account, including:
- Circumstances of the operation (elective vs emergency);
- Disease being treated;
- Acute physiological state of the patient;
- Impact of living with a colostomy, albeit temporarily;
- Use of a specific preoperative regimen of low residue diet and laxatives (so-called "bowel prep").
An anastomosis carries the risk of dehiscence (breakdown of the stitches), which can lead to contamination of the peritoneal cavity, peritonitis, sepsis and death. Colostomy is always safer, but places a societal, psychological and physical burden on the patient. The choice is by no means an easy one and is rife with controversy, being a frequent topic of heated debate among surgeons all over the world.
- Right hemicolectomy and left hemicolectomy refer to the resection of the ascending colon (right) and the descending colon (left), respectively. When part of the transverse colon is also resected, it may be referred to as an extended hemicolectomy
- Transverse colectomy is also possible, though uncommon.
- Sigmoidectomy is a resection of the sigmoid colon, sometimes including part or all of the rectum (proctosigmoidectomy). When a sigmoidectomy is followed by terminal colostomy and closure of the rectal stump, it is called a Hartmann operation; this is usually done out of impossibility to perform a "double-barrel" or Mikulicz colostomy, which is preferred because it makes "takedown" (reoperation to restore normal intestinal continuity by means of an anastomosis) considerably easier.
- When the entire colon is removed, this is called a total colectomy, also known as Lane's Operation. If the rectum is also removed, it is a total proctocolectomy.
- Subtotal colectomy is resection of part of the colon or a resection of all of the colon without complete resection of the rectum.
- Bucher P, Pugin P, Ph Morel (2008). "Single port access laparoscopic right hemicolectomy.". Int J Colorectal Dis 23 (10): 1013–6. doi:10.1007/s00384-008-0519-8. PMID 18607608.
- Enersen, Ole Daniel. "Lane's operation". whonamedit.com. Retrieved 2009-07-19.
- Oakley JR, Lavery IC, Fazio VW, Jagelman DG, Weakley FL, Easley K (1985). "The fate of the rectal stump after subtotal colectomy for ulcerative colitis". Dis. Colon Rectum 28 (6): 394–6. doi:10.1007/BF02560219. PMID 4006633.
- Lambert, Edward C. (1978). Modern medical mistakes. Indiana University Press. p. 18. ISBN 0-253-15425-1.
- "How I Do It" — Removing large or sessile colonic polyps. Dr. Brian Saunders MD FRCP; St. Mark’s Academic Institute; Harrow, Middlesex, UK. (Possible alternative to colectomy for removal of polyps.) Retrieved April 9, 2008.