Editing Large intestine (section)

===Colonoscopy===
{{Main|Colonoscopy}}
[[File:Colonoscopy splenic flexure.jpg|thumb|Colonoscopy image, [[splenic flexure]],<br />normal [[mucosa]]. The [[spleen]] can be seen through it]]
[[Colonoscopy]] is the [[endoscopy|endoscopic]] examination of the large intestine and the [[Anatomical terms of location#Proximal and distal|distal]] part of the [[ileum|small bowel]] with a [[CCD camera]] or a [[fiber optic]] camera on a flexible tube passed through the [[Human anus|anus]]. It can provide a visual diagnosis (e.g. [[Peptic ulcer|ulceration]], [[Colorectal polyp|polyps]]) and grants the opportunity for [[biopsy]] or removal of suspected [[colorectal cancer]] lesions. Colonoscopy can remove polyps as small as one millimetre or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. It takes 15 years or fewer for a polyp to turn cancerous.

Colonoscopy is similar to [[sigmoidoscopy]]—the difference being related to which parts of the colon each can examine. A colonoscopy allows an examination of the entire colon (1200–1500&nbsp;mm in length). A sigmoidoscopy allows an examination of the distal portion (about 600&nbsp;mm) of the colon, which may be sufficient because benefits to cancer survival of colonoscopy have been limited to the detection of lesions in the distal portion of the colon.<ref name="Baxter09">{{cite journal|vauthors=Baxter NN, Goldwasser MA, Paszat LF, Saskin R, Urbach DR, Rabeneck L |title=Association of colonoscopy and death from colorectal cancer |journal=Ann. Intern. Med. |volume=150 |issue=1 |pages=1–8 |date=January 2009 |pmid=19075198 |doi=10.7326/0003-4819-150-1-200901060-00306 |s2cid=24130424 |doi-access= }} [http://www.media.dssimon.com/taperequest/acp50_study.pdf as PDF] {{webarchive|url=https://web.archive.org/web/20120118213536/http://www.media.dssimon.com/taperequest/acp50_study.pdf |date=2012-01-18 }}</ref><ref>{{cite journal |vauthors=Singh H, Nugent Z, Mahmud SM, Demers AA, Bernstein CN |title=Surgical resection of hepatic metastases from colorectal cancer: a systematic review of published studies |journal=Am J Gastroenterol |volume=105 |issue=3 |pages=663–673 |date=March 2010 |pmid=19904239 |doi=10.1038/ajg.2009.650 |s2cid=11145247 }}</ref><ref>{{cite journal |vauthors=Brenner H, Hoffmeister M, Arndt V, Stegmaier C, Alterhofen L, Haug U |title=Protection from right- and left-sided colorectal neoplasms after colonoscopy: population-based study |journal=J Natl Cancer Inst |volume= 102|issue= 2|pages=89–95 |date=January 2010 |pmid=20042716 |doi=10.1093/jnci/djp436 |s2cid=1887714 |doi-access=free }}</ref>

A sigmoidoscopy is often used as a screening procedure for a full colonoscopy, often done in conjunction with a stool-based test such as a fecal occult blood test (FOBT), fecal immunochemical test (FIT), or multi-target stool DNA test (Cologuard) or blood-based test, SEPT9 DNA methylation test (Epi proColon).<ref>{{cite journal |last1=Tepus |first1=M |last2=Yau |first2=TO |title=Non-Invasive Colorectal Cancer Screening: An Overview |journal=Gastrointestinal Tumors |date=20 May 2020 |volume=7 |issue=3 |pages=62–73 |doi=10.1159/000507701|pmid=32903904 |pmc=7445682 |doi-access=free }}</ref> About 5% of these screened patients are referred to colonoscopy.<ref>{{cite journal|vauthors=Atkin WS, Edwards R, Kralj-Hans I, etal |title=Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial |journal=Lancet |volume=375 |issue=9726 |pages=1624–33 |date=May 2010 |pmid=20430429 |doi=10.1016/S0140-6736(10)60551-X |s2cid=15194212 |doi-access=free }} [http://www.foroaps.org/blogevidencia/wp-content/uploads/2010/08/once_only_sigmoid.pdf as PDF] {{webarchive|url=https://web.archive.org/web/20120324041415/http://www.foroaps.org/blogevidencia/wp-content/uploads/2010/08/once_only_sigmoid.pdf |date=2012-03-24 }}</ref>

[[Virtual colonoscopy]], which uses 2D and 3D imagery reconstructed from [[computed tomography]] (CT) scans or from [[nuclear magnetic resonance]] (MR) scans, is also possible, as a totally [[non-invasive (medical)|non-invasive]] medical test, although it is not standard and still under investigation regarding its diagnostic abilities. Furthermore, virtual colonoscopy does not allow for therapeutic maneuvers such as polyp/tumour removal or biopsy nor visualization of lesions smaller than 5 millimeters.  If a growth or polyp is detected using CT colonography, a standard colonoscopy would still need to be performed. Additionally, surgeons have lately been using the term [[pouchoscopy]] to refer to a colonoscopy of the [[ileo-anal pouch]].