Editing Ulcerative colitis (section)

=== Differential diagnosis ===
Several conditions may present in a similar manner as ulcerative colitis and should be excluded. Such conditions include: Crohn's disease, infectious colitis, [[nonsteroidal anti-inflammatory drug]] enteropathy, and [[irritable bowel syndrome]]. Alternative causes of colitis should be considered, such as [[ischemic colitis]] (inadequate blood flow to the colon), [[radiation colitis]] (if prior exposure to [[radiation therapy]]), or [[chemical colitis]]. [[Pseudomembranous colitis]] may occur due to [[Clostridioides difficile infection|''Clostridioides difficile'' infection]] following administration of antibiotics. ''[[Entamoeba histolytica]]'' is a protozoan parasite that causes intestinal inflammation. A few cases have been misdiagnosed as UC with poor outcomes occurring due to the use of corticosteroids.<ref>{{cite journal | vauthors = Shirley DA, Moonah S | title = Fulminant Amebic Colitis after Corticosteroid Therapy: A Systematic Review | journal = PLOS Neglected Tropical Diseases | volume = 10 | issue = 7 | pages = e0004879 | date = July 2016 | pmid = 27467600 | pmc = 4965027 | doi = 10.1371/journal.pntd.0004879 | doi-access = free }}</ref>

The most common disease that mimics the symptoms of ulcerative colitis is Crohn's disease, as both are inflammatory bowel diseases that can affect the colon with similar symptoms. It is important to differentiate these diseases since their courses and treatments may differ. In some cases, however, it may not be possible to tell the difference, in which case the disease is classified as indeterminate colitis.<ref>{{cite journal | vauthors = Tremaine WJ | title = Is indeterminate colitis determinable? | journal = Current Gastroenterology Reports | volume = 14 | issue = 2 | pages = 162–165 | date = April 2012 | pmid = 22314810 | doi = 10.1007/s11894-012-0244-x | s2cid = 40346031 }}</ref> Crohn's disease can be distinguished from ulcerative colitis in several ways. Characteristics that indicate Crohn's include evidence of disease around the anus (perianal disease). This includes anal fissures and abscesses as well as fistulas, which are abnormal connections between various bodily structures.<ref>{{cite journal |last1=Kim |first1=B. |last2=Barnett |first2=J. L. |last3=Kleer |first3=C. G. |last4=Appelman |first4=H. D. |date=November 1999 |title=Endoscopic and histological patchiness in treated ulcerative colitis |url=https://pubmed.ncbi.nlm.nih.gov/10566726/ |journal=The American Journal of Gastroenterology |volume=94 |issue=11 |pages=3258–3262 |doi=10.1111/j.1572-0241.1999.01533.x |issn=0002-9270 |pmid=10566726|hdl=2027.42/74642 |s2cid=11446833 |hdl-access=free }}</ref>

Infectious colitis is another condition that may present in similar manner to ulcerative colitis. Endoscopic findings are also oftentimes similar. One can discern whether a patient has infectious colitis by employing tissue cultures and stool studies. Biopsy of the colon is another beneficial test but is more invasive.

Other forms of colitis that may present similarly include radiation and diversion colitis. Radiation colitis occurs after irradiation and often affects the rectum or sigmoid colon, similar to ulcerative colitis. Upon histology radiation colitis may indicate eosinophilic infiltrates, abnormal epithelial cells, or fibrosis. Diversion colitis, on the other hand, occurs after portions of bowel loops have been removed. Histology in this condition often shows increased growth of lymphoid tissue.

In patients who have undergone transplantation, graft versus host disease may also be a differential diagnosis. This response to transplantation often causes prolonged diarrhea if the colon is affected. Typical symptoms also include rash. Involvement of the upper gastrointestinal tract may lead to difficulty swallowing or ulceration. Upon histology, graft versus host disease may present with crypt cell necrosis and breakdown products within the crypts themselves.<ref>{{cite journal |last1=Woodruff |first1=J. M. |last2=Hansen |first2=J. A. |last3=Good |first3=R. A. |last4=Santos |first4=G. W. |last5=Slavin |first5=R. E. |date=December 1976 |title=The pathology of the graft-versus-host reaction (GVHR) in adults receiving bone marrow transplants |url=https://pubmed.ncbi.nlm.nih.gov/11596/ |journal=Transplantation Proceedings |volume=8 |issue=4 |pages=675–684 |issn=0041-1345 |pmid=11596}}</ref>

{{Findings in CD vs. UC}}