Investigations
1st investigations to order
stool studies for infective pathogens
Test
Infective pathogens should be actively sought both for first presentations of possible disease and in those with known UC presenting with symptoms of a flare-up (as patients with inflammatory bowel disease [IBD] are at higher risk of infection with pathogenic organisms).
Between 5% and 47% of cases of newly diagnosed or relapsing IBD are associated with Clostridium difficile infection.[23]
Stool studies should be obtained, including comprehensive culture and C difficile toxin A and B immunoassay, even in patients with a relapse of known UC.[7][23][27] WBCs may be present in the stool with negative stool culture.
Result
negative culture and Clostridium difficile toxins A and B; WBC present
faecal calprotectin (FC)
Test
FC can be used in patients with UC as a non-invasive marker of disease activity and to assess response to therapy and relapse.[23] In the UK, FC testing is recommended in patients <60 years old to exclude inflammatory causes for recent onset lower gastrointestinal symptoms.[7][27][28][29] It is elevated when there is bowel inflammation and correlates with endoscopic and histological gradings of disease severity.
FC testing is useful in supporting clinicians in the differential diagnosis of irritable bowel syndrome/inflammatory bowel disease (IBD) and can prevent unnecessary referrals for colonoscopy. In those with an established diagnosis of IBD this test can be useful to assess for ongoing bowel inflammation.[27][28][29][30]
Result
elevated faecal calprotectin
FBC
Test
Easy, not expensive, and widely available. FBC may show leukocytosis, thrombocytosis, and anaemia.[27]
Result
variable degree of anaemia, leukocytosis, or thrombocytosis
comprehensive metabolic panel (including LFTs)
Test
Easy, not expensive, and widely available; liver tests should be checked every 6 to 12 months for surveillance of primary sclerosing cholangitis.
Result
hypokalaemic metabolic acidosis; elevated sodium and urea; elevated alkaline phosphatase, bilirubin, aspartate aminotransferase, and alanine aminotransferase; hypoalbuminaemia
erythrocyte sedimentation rate (ESR)
Test
Easy, not expensive, and widely available. ESR may be elevated.[27]
Result
variable degree of elevation, although >30mm/hour is suggestive of a severe flare-up
CRP
Test
Easy, not expensive, and widely available. A persistently raised CRP >45 mg/L during a severe flare-up and following a 3-day course of intravenous hydrocortisone suggests that unless treatment is changed, surgery may be necessary.
CRP ≥12 mg/L has been suggested as a sensitive cut-off for determining UC severity.[31]
Result
variable degree of elevation
plain abdominal radiograph
Test
This test gives an approximate estimate of the extent of disease because an ulcerated colon usually contains no solid faeces. Easy, not expensive, and widely available; ordered when initial presentation or subsequent relapses are associated with signs and symptoms of an acute abdomen.[27]
Result
dilated loops with air-fluid level secondary to ileus; free air is consistent with perforation; in toxic megacolon, the transverse colon is dilated to ≥6 cm in diameter
flexible sigmoidoscopy
Test
Less expensive than colonoscopy; does not require sedations; can be performed in the surgery.
Result
findings are as in colonoscopy, but examination is limited to distal colon
colonoscopy
Test
Colonoscopy is expensive, requires full bowel preparation and sedation, and should be performed in a special setting (endoscopy suite).
Indicated to assess the extent of disease if sigmoidoscopy suggests proximal extension. Used in patients with UC who are not responding well to treatment to rule out infections (particularly cytomegalovirus and Clostridium difficile), and to evaluate the need for surgery.[36]
Intubation and biopsy of the terminal ileum should be possible in most patients with inflammatory bowel disease.
Also, essential for cancer screening in long-standing cases.
Result
rectal involvement, continuous uniform involvement, loss of vascular marking, diffuse erythema, mucosal granularity, normal terminal ileum (or mild 'backwash' ileitis in pancolitis)
biopsies
Test
Biopsies should be obtained at the time of endoscopy even if the mucosa appears unremarkable. Biopsies are essential for diagnosis and differential diagnosis.[19]
A minimum of two biopsies from at least five sites along the colon, including the rectum and terminal ileum, should be obtained.[32][33][34]
Inflammatory bowel disease may be distinguished from acute infectious colitis by the presence of crypt architectural changes such as crypt branching or sparsity; these features take several weeks to develop and are not likely to be present in infectious colitis.
Result
continuous distal disease, mucin depletion, basal plasmacytosis, diffuse mucosal atrophy, absence of granulomata, and anal sparing
Investigations to consider
CT scan
Test
Oral and intravenous contrast is needed. Should be avoided in patients with significant renal dysfunction.
Ordered when complications or other diagnoses are being considered.
Result
biliary dilation suggests primary sclerosing cholangitis
intestinal ultrasound
Test
The use of intestinal ultrasound has grown in recent years as a tool for objectively assessing and monitoring IBD activity including in UC. It is a non-invasive, radiation-free alternative to endoscopies and biomarkers which enables real-time, high-resolution examination of the bowel wall, mesentery, and adjacent structures.[35] The American Gastroenterology Association (AGA) suggests that it could be used as a screening tool in a similar way to FC, to rule out IBD, or to monitor disease activity.[35]
Result
increased bowel wall thickness or hyperaemia
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