Approach

Inflammatory bowel disease (IBD) classically presents with bloody diarrhoea with rectal urgency and tenesmus. Typically the onset is gradual with progression over weeks but it can be acute.[23][24]​ Rectal bleeding is reported by more than 90% of patients so it should be an important consideration in patients who have bloody diarrhoea and/or diarrhoea with signs of systemic inflammation.[25]

Diagnosis requires, at a minimum, negative stool culture and some form of sigmoidoscopy or colonoscopy.[23]

History and examination

In addition to the presence of bloody diarrhoea, further suggestive features include:[23]

  • a history of lower abdominal pain

  • faecal urgency

  • tenesmus (a feeling of needing to pass a stool even though the colon is empty), and

  • the presence of extraintestinal manifestations, particularly those related to disease activity, such as erythema nodosum and acute arthropathy.

UC should be suspected in patients with primary sclerosing cholangitis, as up to 70% have underlying inflammatory bowel disease.[26]

Initial work-up

The initial work-up for all patients should include basic laboratory tests (full blood count [FBC], metabolic panel, inflammatory markers), stool studies, and either a colonoscopy or flexible sigmoidoscopy to visualise the mucosa and obtain a biopsy.[23][27]

An abdominal x-ray is ordered when initial presentation or subsequent relapses are associated with signs and symptoms of an acute abdomen.[7][27]

If there is uncertainty about the type of inflammatory bowel disease, an upper gastrointestinal work-up should be carried out to assess for Crohn’s disease present in the upper gastrointestinal tract.[27]

Stool studies

Between 5% and 47% of cases of newly diagnosed or relapsing inflammatory bowel disease 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] ​​​White blood cells may be present in the stool with negative stool culture.

Faecal calprotectin (FC) testing

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 when considering inflammatory bowel disease in the differential diagnosis of irritable bowel syndrome. It can help determine which patients require urgent endoscopy and can prevent unnecessary referrals for colonoscopy (>60% in younger patients presenting with lower gastrointestinal symptoms, the majority of whom will not have inflammatory bowel disease).[28] In those with an established diagnosis of IBD this test can be useful to assess for ongoing bowel inflammation.[27][28][29][30]​​

Laboratory studies

FBC may show leukocytosis, thrombocytosis, and anaemia.[7][27] ​​​

Inflammatory markers (erythrocyte sedimentation rate and C-reactive protein) may be raised.​[7][27][31] Metabolic abnormalities can include hypokalaemic metabolic acidosis secondary to diarrhoea; elevated sodium and urea secondary to dehydration; elevated alkaline phosphatase, bilirubin, aspartate aminotransferase, and alanine aminotransferase in patients with concomitant primary sclerosing cholangitis; and hypoalbuminaemia secondary to malnourishment or as an acute-phase reactant.[7]

Sigmoidoscopy and biopsy

Flexible sigmoidoscopy can be performed in the endoscopy unit without sedation or full bowel prep but can only visualise the distal colon. Full bowel prep and colonoscopy is required if disease is suspected to extend beyond the distal bowel on the basis of x-ray. Endoscopic evaluation with histological confirmation is the key to diagnosis, but histological features overlap considerably between UC, Crohn's disease, and infectious colitis; hence, the diagnosis is based on the combination of history, endoscopic findings, histology, and microbiology, rather than on any single modality.[7]​ During acute flares endoscopic examination should be limited to flexible sigmoidoscopy without bowel prep, due to the increased risk of perforation.

For a reliable diagnosis of IBD, ileocolonoscopy should be performed. 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]

Imaging

Although generally reserved for those with severe or extensive colitis, plain abdominal radiography can help to rule out toxic megacolon or perforation at first presentation or during subsequent acute relapses.[27]

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]

Follow-up tests

Colonoscopy requires full bowel preparation and sedation. It is needed to assess the extent of disease if sigmoidoscopy suggests proximal extension. It is also indicated in patients with UC who are not responding well to treatment, in order to rule out infections (particularly cytomegalovirus and C difficile) and assess the need for surgery.[36] Colonoscopy is also essential for cancer screening in long-standing cases.

Contrast computed tomography should be ordered when complications (e.g., primary sclerosing cholangitis) or other diagnoses are being considered.​[23]

Venepuncture and phlebotomy animated demonstration
Venepuncture and phlebotomy animated demonstration

How to take a venous blood sample from the antecubital fossa using a vacuum needle.

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