Ulcerative Colitis vs Crohn’s Disease

Introduction

There are two main types of idiopathic inflammatory bowel disease (IBD) – ulcerative colitis and Crohn’s disease.

Although both share many similarities in the signs, symptoms and pharmacological management, key distinctions can be made from the location of the inflammation and the histopathological findings.

Ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease with a relapsing-remitting course. The disease is localised to the colon, with the rectum being the most commonly affected site.¹

The underlying aetiology isn’t clear, but it is thought to be linked to environmental and epigenetic factors, including a positive family history.² Smoking is thought to protect against developing ulcerative colitis.³

Clinical features

Clinical features of ulcerative colitis include:¹

• Diarrhoea (often bloody ± mucus)
• Faecal urgency/incontinence
• Tenesmus
• Abdominal pain (often felt in the LLQ) and bloating
• Fatigue/malaise
• Anorexia
• Fever
• Weight loss

Investigations

Relevant blood tests include:^1,5

• Full blood count: may show anaemia, leukocytosis and/or thrombocytosis
• Urea & electrolytes: as a baseline
• Liver function tests: surveillance for primary sclerosing cholangitis
• CRP/ESR
• Thyroid function tests: exclude hyperthyroidism
• Serum folate, ferritin, vitamin D, vitamin B12
• Coeliac screen: to exclude this as a diagnosis

Relevant stool tests include:

• Faecal calprotectin: raised in inflammatory bowel disease but not irritable bowel syndrome (IBS)
• Stool microscopy and culture (screen for Clostridium difficile toxin and other infectious microorganisms)

Diagnosis

Ulcerative colitis is usually diagnosed with endoscopic imaging and a biopsy. Options include:⁵

• Flexible sigmoidoscopy: imaging is limited to the distal colon but requires less bowel preparation than a colonoscopy
• Colonoscopy: may be required if disease extends more proximally
• Abdominal X-ray: sometimes requested to screen for bowel obstruction or toxic megacolon
• CT scan with contrast: may be considered to rule out other pathologies and diagnoses

Management

Management is broadly divided into inducing remission and maintaining remission.

Pharmacological options include:¹

• Aminosalicylates (e.g. mesalazine and sulfasalazine)
• Corticosteroids (can be given topically, orally or intravenously)
• Calcineurin inhibitors (e.g. tacrolimus or ciclosporin)
• Immunosuppressants (e.g. thiopurines or methotrexate)
• Biologics (e.g. infliximab and adalimumab)

Surgical management

There are a few different options for surgery, including a subtotal colectomy with ileostomy, colectomy with ileo-rectal anastomosis, proctocolectomy with ileostomy and restorative proctocolectomy with ileo-anal pouch.⁸

Crohn’s disease

Like ulcerative colitis, Crohn’s disease is a relapsing-remitting chronic inflammatory disease of the gastrointestinal tract.

However, Crohn’s disease can affect any part of the gastrointestinal tract.⁹

Again, the aetiology of Crohn’s disease is thought to be linked to a mix of genetic factors, including a positive family history and environmental/lifestyle factors, with smoking being one of the key risk factors.^10,11

Clinical features

Clinical features of Crohn’s disease include:^9,12

• Persistent diarrhoea (may be bloody ± mucus ± pus)
• Abdominal pain (RLQ pain/mass may be reported if terminal ileum affected)
• Tenesmus
• Fever
• Malaise/fatigue
• Anorexia
• Aphthous ulcers
• Perianal lesions (fissures, abscesses, fistulas)
• Weight loss/faltering growth

Investigations

Relevant blood tests include:^9,12

• Full blood count: may show anaemia, leukocytosis and/or thrombocytosis
• Urea & electrolytes: as a baseline
• Liver function tests: surveillance for primary sclerosing cholangitis
• Vitamin B12, vitamin D and folate
• CRP/ESR
• Iron studies: may show iron deficiency
• Coeliac screen: to exclude this as a diagnosis
• Yersinia enterocolitica serology: important to exclude

Relevant stool tests include:

• Faecal calprotectin: raised in inflammatory bowel disease but not irritable bowel syndrome (IBS)
• Stool microscopy and culture (screen for Clostridium difficile toxin and other infectious microorganisms)

Diagnosis

Diagnosis is normally achieved with a colonoscopy with multiple biopsies.^9,12

Other imaging options include:

• MRI of the abdomen/pelvis
• CT abdomen: helps look for other features, including abscesses and fistulas
• Abdominal X-ray: can visualise bowel loop distension and rule out other pathologies
• Abdominal/pelvic ultrasound

Management

Again, management focuses on inducing and maintaining remission.

Pharmacological options include:⁹

• Corticosteroids
• Immunosuppressants (e.g thiopurines or methotrexate)
• Biologics (e.g infliximab and adalimumab)
• Aminosalicylates (e.g mesalazine and sulfasalazine)

Surgical management¹⁵

There are several different options for surgery, including strictureplasty, ileocaecal resection, a segmental colectomy, right hemicolectomy, subtotal colectomy with ileostomy, colectomy with ileorectal anastomosis and proctocolectomy with ileostomy.

As Crohn’s disease can affect the entire gastrointestinal tract, surgery is not curative but can greatly improve symptoms.

Summary table

Table 1. Table displaying the key differences between ulcerative colitis and Crohn’s disease

References

1. NICE CKS. Ulcerative colitis [Internet]. NICE. 2020. Available from: [LINK]
2. Childers RE, Eluri S, Vazquez C, Weise RM, Bayless TM, Hutfless S. Family history of inflammatory bowel disease among patients with ulcerative colitis: A systematic review and meta-analysis. Journal of Crohn’s and Colitis. 2014 Nov;8(11):1480–97.
3. Guslandi. Nicotine treatment for ulcerative colitis. British Journal of Clinical Pharmacology [Internet]. 2001 Dec 24;48(4):481–4. Available from: [LINK]
4. Lynch WD, Hsu R. Ulcerative colitis [Internet]. Nih.gov. StatPearls Publishing; 2022. Available from: [LINK]
5. BMJ Best Practice. Ulcerative colitis [Internet]. bestpractice.bmj.com. 2023 [cited 2023 Dec 20]. Available from: [LINK]
6. DeRoche TC, Xiao SY, Liu X. Histological evaluation in ulcerative colitis. Gastroenterology Report. 2014 Aug 1;2(3):178–92.
7. Singh V, Johnson K, Yin J, Lee S, Lin R, Yu H, et al. Chronic Inflammation in Ulcerative Colitis Causes Long-Term Changes in Goblet Cell Function. Cellular and Molecular Gastroenterology and Hepatology. 2022;13(1):219–32.
8. Surgery for Ulcerative Colitis [Internet]. Crohnsandcolitis.org.uk. 2022. Available from: [LINK]
9. NICE CKS. Crohn’s disease [Internet]. NICE. 2020. Available from: [LINK]
10. Torres J, Gomes C, Jensen CB, Agrawal M, Ribeiro-Mourão F, Jess T, et al. Risk Factors for Developing Inflammatory Bowel Disease Within and Across Families with a Family History of IBD. Journal of Crohn’s and Colitis. 2022 Aug 9;17(1).
11. Ss M, Ks M, Re S, Ca H, S G. Smoking and Inflammatory Bowel Disease: A Meta-Analysis [Internet]. Mayo Clinic proceedings. 2006. Available from: [LINK]
12. BMJ Best Practice. Crohn’s disease [Internet]. bestpractice.bmj.com. 2023 [cited 2023 Dec 18]. Available from: [LINK]
13. McDowell C, Farooq U, Haseeb M. Inflammatory Bowel Disease [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023. Available from: [LINK]
14. Ranasinghe IR, Hsu R. Crohn Disease [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2022. Available from: [LINK]
15. Surgery for Crohn’s Disease [Internet]. crohnsandcolitis.org.uk. 2022. Available from: [LINK]