Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) refers to a relapsing and remitting inflammatory disorder of the gastrointestinal (GI) tract, which may be accompanied by extra-GI manifestations.

What are the main types of IBD?

The term IBD encompasses two types: ulcerative colitis (UC) and Crohn’s disease (CD). CD can affect any part of the GI tract, although in most cases selectively affects the terminal ileum. UC solely impacts the colon and within this, only the superficial layer, the colonic mucosa, is affected. In contrast, CD can affect the whole depth of the intestinal wall. This article will highlight the differences between the two conditions and cover their management.

Figure 1: Differences between the areas affected in CD vs UC (Image source:


The exact cause of IBD is unknown. There is known genetic susceptibility to IBD that may impact components of the immune system but there is likely an environmental role influencing the development of the disease. Overall interaction between genes, environment, host immune response and intestinal microbiota is thought to be implicated in the disease.


IBD commonly follows a bimodal age distribution, whereby incidence is most common between 15-35 years old and in another group between 55-70 years old. Smoking increases the risk of CD but decreases the risk of UC. Flare-ups of IBD is often associated with stress.  

Clinical Features

Features present in both CD and UC
  • Episodic or chronic diarrhoea, often with blood or mucus.
    • Blood is more common in UC than CD.
  • Urgency and tenesmus
    • More common in UC
  • Tender, distended abdomen
  • Crampy abdominal discomfort and pain
    • Cramps usually relieved by defecation are a common feature of UC
  • Systemic features:
    • Fever
    • Tachycardia
    • Anorexia
    • Weight loss
  • Extra-GI manifestations:
    • Clubbing
    • Skin – erythema nodosum (tender red nodules on shins)
    • Joint – large joint polyarthritis, seronegative arthritis e.g. ankylosing spondylitis
    • Eye – conjunctivitis, episcleritis, iritis

Some extra GI manifestations, such as episcleritis and erythema nodosum are related to disease activity. Others such as sacroiliitis are not.

Clinical features specifically in CD
  • Peri-anal disease: Strictures, Fistulae, Abscesses, Skin tags, Fissures
  • Aphthous (painful) mouth ulcers
  • Malabsorption – deficiencies are common as CD commonly affects the small intestine
  • Oxalate renal stones
Clinical features specifically in UC

UC is associated with a condition known as primary sclerosing cholangitis (PSC); which is an inflammatory disease that leads to progressive fibrosis of the bile ducts, which can eventually lead to liver damage. In many cases, PSC often presents before IBD.

Assessing Disease Severity

Severity in Ulcerative Colitis

In UC, the severity of the condition is determined using a classification known as Truelove and Witt’s. It uses bowel frequency, anaemia, fever and bleeding to assess whether the condition is mild, moderate or severe. The table below highlights the criteria for the 3 different severity classifications.

Mild UCModerate UCSevere UC
Motions/day< 44-6> 6
Rectal bleedingSmallModerateLarge
T° at 6amApyrexial37.1 – 37.8°C> 37.8°C
Resting pulse< 70 beats/min70 – 90 beats/min> 90 beats/min
Haemoglobin> 110 g/L105 – 110 g/L< 105 g/L
ESR (CRP)< 30 (CRP >16mg/L)  > 30 (CRP >45mg/L)
Severity in Crohn’s Disease

In CD, the severity is determined by a scoring system known as Harvey-Bradshaw Index (HBI). An HBI score is calculated based on 5 domains and points are given per domain following which the total score is calculated. A score <5 indicates remission, mild disease would score 5-7, moderate disease would score 8-16 and severe disease >16.

General Wellbeing    
 0 = very well1 = slightly below average2 = poor3 = very poor 4= terrible
Abdominal Pain    
0 = none1 = mild2 = moderate3= severe 
No. of liquid stools per day  1 point for each episode per day  
Abdominal Mass    
0 = none 1 = dubious2 = definite3 = definite & tender 
Score 1 point for each of the following:Arthralgia
– Uveitis
– Aphthous ulcers
Anal fissures
– New fistulas
– Abscesses
 – Erythema nodosum
– Pyoderma gangrenosum

Radiology features in IBD

In UC, a key feature is the loss of the haustra in the colon, which is known as ‘leadpipe’ colon. In CD, the ulcers along the GI tract lead to a cobblestone appearance. Strictures in CD cause narrowing of the bowel lumen at various locations, which is shown as the ‘string sign’ in a barium study.  

Leadpipe Colon
Figure 2: Appearance of a ‘leadpipe’ colon. On the left side, there are no haustra as there is with the other parts of the colon. (Image source:
String Sign
Figure 3: On the bottom of the image, the ‘string sign’ is visible as there is a stricture in that segment of bowel. (Image source:

Differential Diagnoses


In any patient presenting with diarrhoea, infective causes should be excluded. In patients who have been in hospital or recently had a course of antibiotics, one should test for C.difficile. Other infections to exclude are E.coli, shigella, salmonella, yersinia and parasites. Even in patients with known IBD and presumed to have an acute flare, infective causes should still be considered. Cytomegalovirus (CMV) is an important infection to be aware of in patients with known IBD. It is a virus that is involved in many inflammatory processes and therefore is closely associated with IBD. Therefore, a presumed flare-up of IBD can often mask CMV colitis as the diagnosis.

Other differentials

  • Ileocolonic TB – similar features to CD (terminal ileitis)
  • CD needs to be differentiated from other causes of malabsorption e.g. pancreatic insufficiency
  • Ischaemic colitis
  • Coeliac disease – symptoms can mimic IBD (abdominal cramps, diarrhoea, malabsorption)
  • It is also important to rule out colonic malignancy, especially in older people



  • FBC
    • To detect if any evidence of anaemia or infection.
    • Hb is  important in classifying severity of UC via the Truelove and Witt’s score
  • ESR and CRP
    • Used as markers of inflammation and part of Truelove and Witt’s score
  • Haematinics
    • Anaemia is common in IBD.
    • B12 and folate deficiencies are specific to CD as this affects the small bowel where they are absorbed (B12 in terminal ileum, folate in duodenum/proximal jejunum)
  • U&Es
    • Important as diarrhoea can cause electrolyte imbalance and trigger an acute kidney injury (AKI)


  • ASCA Abs: positive in IBD overall
  • pANCA Abs: primarily positive in UC, tends to be negative in CD
  • Coeliac screen antibodies: anti-tissue transglutaminase (tTG), anti-endomysial (EMA) and anti-gliadin (AGA).

Stool sample

  • Faecal calprotectin- detects any evidence of intestinal inflammation via the stool
  • C.difficile test and stool MC&S – this is key to rule out any infective causes of diarrhoea


  • Abdominal x-ray (AXR)
    • To rule out complications of IBD flares (obstruction, toxic megacolon) and to assess bowel appearances to identify features of CD vs UC
    • Figure 3 below shows the appearance of toxic megacolon
  • Barium follow-through studies (to be requested by specialists)
    • Involves patient drinking barium-based contrast and real-time x-ray images used to image the bowel. It can highlight strictures and fistulas in CD.
  • Small bowel MRI (to be requested by specialists)
    • Used to produce detailed images of the small bowel in CD
Toxic megacolon
Figure 4: Toxic megacolon can be seen on this AXR film. It is defined as colon diameter >6cm. (Image source:


Scoping is an excellent way to capture images of the bowel lumen. In an active flare, an unprepared flexible sigmoidoscopy is used as bowel prep can acutely worsen the diarrhoea. Once the disease is controlled, a full colonoscopy can be done to define the extent of the disease. Biopsies can be taken during scopes and this can help distinguish between CD and UC. It is also important to test for CMV in the biopsy tissues taken given the previously discussed close relationship between IBD flares and CMV colitis.


There is a range of complications that can arise from IBD, which are as follows:

  • Bowel obstruction from strictures in CD
  • Toxic megacolon: This is where the colon becomes massively dilated, which can lead to shock. It is an emergency and usually needs surgery to prevent a perforation of the bowel.
  • Bowel perforation
  • VTE: Need to give prophylaxis to all inpatients provided no contraindications
  • Risk of colonic cancer if long-term colitis
  • Abscess formation
  • Fistulae
  • Vitamin deficiencies e.g. osteomalacia
  • Gallstones and steatorrhea
  • Renal stones
  • Anaemia: Normocytic (chronic disease), microcytic (iron-deficiency) or macrocytic (B12 deficiency in terminal ileal disease)
  • Hypokalaemia and other electrolyte imbalances due to diarrhoea


Managing an acute admission related to IBD
  • A-E approach: As with any acute medical scenario, start with an A-E approach. Key things you want to make sure is that the patient is not in shock or that they do not have any dangerous electrolyte imbalances secondary to diarrhoea.
  • History
  • Abdominal examination & Digital rectal examination (DRE)
  • Regular observations
  • ECG
  • CXR, AXR
  • Bloods – FBC, ESR, CRP, U&Es, haematinics, serology
  • Stool: Chart to monitor frequency & consistency, Sample for C. difficile, MC&, faecal calprotectin
  • Interventions
    • Keep patient nil by mouth (NBM) & give IV hydration & electrolyte replacement
    • IV hydrocortisone 100mg QDS
    • Nutritional support/dietician review
    • VTE prophylaxis
    • Escalate to gastroenterologist/IBD nurse
    • Consider tuberculosis (TB) spot tests, Hepatitis B & C, HIV in anticipation of starting biological therapy (as these can increase risk of worsening disease or reactivation)
    • Thiopurine methyltransferase (TPMT) levels if considering starting management on thiopurines (as low levels can impact drug metabolism)
    • Ensure patient added to IBD MDT lists (if it exists in your local hospital)
Inducing remission

The medications used to induce remission in CD and UC are different. Generally, the following is used as displayed by the table below, however medications are often tailored based on the patient’s preference, comorbidities and response.

 1st line2nd lineOthers
Ulcerative colitisOral 5-ASA (can be PR if distal disease primarily)Oral prednisoloneInfliximab can be used as ‘rescue therapy’ in an acute refractory severe attack of UC If this fails, then surgery is considered
Crohn’s diseaseOral steroids5-ASAAzathioprine Mercaptopurine Infliximab – Is used in patients that do not respond to other types of treatment If all options fail to control acute attack, then surgery is considered
Maintaining remission
 1st line2nd line
Ulcerative colitisOral 5-ASA (can be given rectally if distal disease primarily)Azathiopurine/mercaptopurine
Crohn’s diseaseAzathioprine/mercaptopurineMethotrexate

In CD,  quitting smoking is emphasised as it can help maintain remission. An elemental diet can also be used to control symptoms; this involves nutrition that is already in an easily absorbable form. Many CD patients may also require B12, iron and fat-soluble vitamin supplements depending on the localisation of their disease.

It is important that patients are given contact details of IBD nurses so that they can contact them if they need any advice or have any queries. Patients will likely be followed up in clinic by IBD nurses/gastroenterologists.

Surgical management

In an acute setting, surgery is considered if symptoms do not respond at all to various medical treatments within 72 hours.

In a chronic picture, surgery is considered when medical therapy fails to alleviate symptoms and so bowel resection is needed. In CD, surgery is especially considered when strictures and fistulas are present. Surgery in CD is aimed so that as much bowel can be preserved as possible. In UC, however, subtotal colectomies are the most common as it is desirable to remove the whole colon to prevent disease recurrence in the parts that would otherwise be left in-situ.

Surgery is also needed for emergency situations in IBD such as:

  • Massive haemorrhage
  • Fulminating colitis with toxic megacolon
  • Bowel perforation
  • Bowel obstruction


Written by Dr Zahra Mohamedali (FY1)
Checked & Reviewed by Dr Mohammed El-Naggar (Gastroenterology Registrar)

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