Crohn’s Disease CD

Research

Introduction

  • CD = Crohn’s Disease

  • UC = Ulcerative Colitis

  • IBD = Inflammatory Bowel Disease = both UC + CD

Patterns of disease

  • 80% of patients have small bowel involvement, usually distal ileum

  • 50% of patients have ileocolitis

  • 20% of patients have the disease only in colon

  • 30% have perianal disease

  • 10% have involvement of mouth, stomach, duodenum

Incidence

  • Lower in Asian and Middle Eastern countries

  • However, the incidence is rising in newer industrialised countries in Africa, Asia, and South America

  • Highest rates are in Scandinavia with Sweden, Finland and Denmark at around 9 in 100 = 1 in 11

  • The rate in the USA at 422/100,000 = 1 in 250

  • Lowest rate in the Caribbean at 6/100,000 = 1 in 16,000

  • North / south gradient with high incidence in countries closer to the poles and lower closer to the equator

  • Possible link to less sunlight and lower Vitamin D

Demographics

  • Onset most common between 15 and 30

  • Bimodal with a second peak between 50 and 80 years

  • Slight female predominance

Risk Factors

  • Smoking is a risk factor for CD but not Ulcerative Colitis UC. Smoking increases the risk of complications e.g. strictures, fistulas

  • Physical activity decreases the risk of CD. One study showed those in the top 20% of physical activity had CD rates of 6/100,000 versus those in the bottom 20% of physical activity at 16/100,000

  • Diet

    • Fibre - particularly fruit and cruciferous vegetables decreased the risk of CD.

    • Fats - Total fat, animal fat, and polyunsaturated fatty acids PUFA increased the risk

    • Vitamin D - Low vitamin D common in CD

  • Sleep deprivation linked to disease flares in UC for those who slept <6 hours or >9 hours. Did not seem to modify the risk of CD

  • Gastroenteritis - links with acute gastroenteritis and developing CD. Population studies showed higher CD rates in patients with documented Samlnoella or Campylobacter gastroenteritis.

  • Medications

    • Antibiotic use is associated with inflammatory bowel disease IBD but unclear if causal relationship.

    • Anti-inflammatory NSAID use may increase the risk of IBD but the magnitude is small.

    • Oral contraception and Hormone Replacement Therapy HRT may increase the risk of IBD but the risk appears small

      • HRT relative risk RR for UC is 1.3 for HRT and 1.5 for oral contraception

      • A second study showed an RR of 1.7 for HRT on UC

    • Isotretinoin - Association but no strong evidence. May be confounded as these people often take antibiotics like Doxycycline first.

  • Appendicectomy - Some studies suggest a higher risk of CD but this may be due to misdiagnosis of the appendicitis which is early incipient CD. Appendicectomy may lower the risk of developing UC for patients with appendicitis or mesenteric adenitis compared to controls.

  • Psychological factors have been studied with inconsistent results. Stress may have a role in the exacerbation of patients with established IBD

  • Obesity - Unclear if associated however accumulation of intra-abdominal fat may contribute to mucosal inflammation. Anoperineal complications appear to happen earlier in patients with CD with obesity.

Nutrition

Malnutrition in IBD can lead to weight loss, growth failure, bone disease, and/or micronutrient deficiencies

Patients with active disease without undernutrition can generally eat what they want. No particular food category can broadly be linked to triggering a disease flare.

Patients with Irritable Bowel Syndrome IBS and IBD may benefit from a low FODMAP diet during flare-ups.

Lactose intolerance is common and lactose restriction can be beneficial in these patients.

Anti-oxidants - Data is not substantial enough to make a recommendation.

Prebiotics - Not enough data to make a recommendation

Fish oil - Not enough data

Clinical Features

  • Abdominal pain - Crampy. If ilial disease then pain is often right lower quadrant. Obstructive symptoms are common. Some patients have no symptoms of CD until obstruction.

  • Diarrhoea - Common. Often intermittent without gross blood. Intermittent diarrhoea with other features of IBD e.g. skin, eye, or joint suggests CD. Diarrhoea happens due to excess fluid secretion, bile salt malabsorption, steatorrhoea, and from fistulas causing bypass of portions of absorptive surface area.

  • Systemic - Weight loss and fever.

  • Transmural inflammation - Leads to

    • Fistulas - connections between two organs (bowel, bladder, skin, vaginal, peritoneum)

    • Phlegmon/abscess - a walled-off pocket

    • Perianal - common. Perianal pain or drainage.

  • Other GIT features

    • Mouth ulcers or gum pain

    • Oesophageal involvement leads to swallowing difficulties

    • Stomach involvement

References