Differentials
Ulcerative colitis (UC)
SIGNS / SYMPTOMS
UC presents with features of colitis including left-sided abdominal pain and bloody diarrhea.
Does not involve small bowel or cause oral or perianal disease.
INVESTIGATIONS
Colonoscopy differentiates most cases of Crohn disease (CD) from UC. UC always involves the rectum and is contiguous versus intermittent. Terminal ileitis may be present in UC with pancolitis due to backwash.
Antiglycan antibodies are more prevalent in CD than in UC, but have a low sensitivity.[71]
Infectious colitis
SIGNS / SYMPTOMS
History of contact with people who are sick, and travel to endemic areas.
INVESTIGATIONS
Stool testing reveals the infectious agent.
Biopsy does not show the typical histologic features of Crohn disease.
Pseudomembranous colitis
SIGNS / SYMPTOMS
History of recent antibiotic use.
Caution should be taken in differentiating the 2 conditions as Clostridium difficile infection may precipitate flare-up of Crohn disease.[70]
INVESTIGATIONS
In the proper clinical setting, a positive test for C difficile toxin is diagnostic of pseudomembranous colitis.
Colonoscopy shows pseudomembranes on top of the mucosa, with no ulceration of the underlying tissue.
Ischemic colitis
SIGNS / SYMPTOMS
Physical findings in ischemic colitis usually do not correlate with the severity of pain.
Most patients have risk factors such as atherosclerotic diseases or hypoperfusion states (e.g., congestive heart failure and hypotension).
INVESTIGATIONS
Colonoscopy shows mucosal friability in the watershed areas of the left colon.
Radiation colitis
SIGNS / SYMPTOMS
History of exposure to external beam radiation therapy.
Symptoms include abdominal pain, tenesmus, and chronic bleeding.
INVESTIGATIONS
Colonoscopy reveals mucosal inflammation that resembles UC with friable, left-sided fibrotic and ulcerative lesions that are continuous. Many patients have bleeding angioectatic vessels.
Yersinia enterocolitica
SIGNS / SYMPTOMS
Y enterocolitica can cause an acute ileitis with a clinical picture resembling acute flare-up of Crohn disease.
INVESTIGATIONS
Colonoscopic findings in Y enterocolitica enterocolitis include involvement of the terminal ileum in almost all patients and, less commonly, the ileocecal valve, cecum, and ascending colon. Small, rounded, or oval mucosal elevations with or without small ulcers in the terminal ileum are suggestive of Y enterocolitica enterocolitis.
Stool cultures and serologic tests confirm the diagnosis.[74]
Intestinal tuberculosis
SIGNS / SYMPTOMS
Can present with weight loss, abdominal pain, and fever, and can cause a terminal ileitis on imaging.
Consider in patients from endemic areas who present with suggestive symptoms, such weight loss and night sweats.[70]
There may be features of tuberculosis (TB) infection elsewhere in the body (e.g., cough, hemoptysis).
INVESTIGATIONS
There may be lymphadenopathy on imaging investigations.
Ileocecal biopsy shows caseating granulomata.
TB infection may be found on tissue staining for acid-fast bacilli, TB culture, or TB polymerase chain reaction, alone or in combination, although yield is low.[69]
Amebiasis
SIGNS / SYMPTOMS
Amebiasis can mimic Crohn disease of the ileum and cecum.
Recent travel to endemic areas is highly suggestive.
INVESTIGATIONS
Stool testing for parasites.
Cytomegalovirus colitis
SIGNS / SYMPTOMS
Immunocompromised patients, including those who have received solid organ transplant, patients on long-term immunosuppressants, or patients with HIV infection or AIDS.
INVESTIGATIONS
Biopsy should be sent for histologic examination, antigen detection, and viral culture. Classic histologic findings include giant cells with cytomegaly and large ovoid or pleomorphic nuclei containing basophilic inclusions.
Colorectal cancer
SIGNS / SYMPTOMS
Increased risk associated with increasing age and a positive family history.
INVESTIGATIONS
CT scan may show primary or secondary disease.
Colonoscopy provides tissue for histologic diagnosis.
Diverticular disease
SIGNS / SYMPTOMS
Commonly presents with left-sided abdominal pain in patients ages 50 years and older.
INVESTIGATIONS
CT scan shows evidence of diverticular disease with surrounding inflammation.
Acute appendicitis
SIGNS / SYMPTOMS
Younger patients.
Pain may start in the periumbilical area, with subsequent localization to the right lower quadrant.
INVESTIGATIONS
CT scan showing inflammation of appendix only.
Ectopic pregnancy
SIGNS / SYMPTOMS
All acute presentations with abdominal pain in women of childbearing age should be considered to be due to an ectopic pregnancy until proven otherwise.
May be a history of amenorrhea, known positive pregnancy test, vaginal bleeding.
INVESTIGATIONS
Urine and or serum beta human chorionic gonadotropin positive.
Pelvic ultrasound may identify a tubal pregnancy.
If rupture is suspected and the patient is hemodynamically unstable, urgent resuscitation and surgery is required.
Pelvic inflammatory disease
SIGNS / SYMPTOMS
Vaginal discharge, dyspareunia, and pelvic pain.
INVESTIGATIONS
Pelvic ultrasonography shows inflammatory changes in the adnexa. Rarely, laparoscopic evaluation is needed.
Endometriosis
SIGNS / SYMPTOMS
Patients usually have cyclical symptoms starting with the menses.
INVESTIGATIONS
Laparoscopy demonstrates the presence of endometrial tissues in the peritoneal cavity.
Irritable bowel syndrome
SIGNS / SYMPTOMS
Chronic change in stool frequency, form, or appearance. Commonly associated with abdominal bloating and passing mucus per rectum.
Spasmodic abdominal pain is often relieved by defecation.
Crohn disease (CD) should be suspected if symptoms are progressive or include bloody or nocturnal diarrhea.
INVESTIGATIONS
Screening blood tests show no evidence of inflammation.
Biopsy does not show typical features of CD.
Fecal calprotectin can help to differentiate inflammatory bowel disease from irritable bowel syndrome, but is not specific for CD.[71]
Microscopic colitis
SIGNS / SYMPTOMS
Chronic watery, nonbloody diarrhea.
Other common symptoms include fecal urgency, fecal incontinence, and nocturnal stools.
More common in patients ages >50 years and in women.
INVESTIGATIONS
Diagnosis is confirmed by ileocolonoscopy with biopsies from the right and left colon.[99] Colonic mucosa has a normal or near-normal gross appearance. Biopsy demonstrates collagenous colitis (i.e., thickened subepithelial collagenous band of ≥10 micrometers (normal <5 micrometers) or lymphocytic colitis (i.e., increased number of intraepithelial lymphocytes of ≥20 per 100 surface epithelial cells (normal <5 micrometers). Both types show an increased inflammatory infiltrate in the lamina propria.[99]
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