Crohn's disease

Key points

1:10000 per year

Peak incidence age 15-30

Unlikely in ages <5

Common in Europe, USA, Ashkenazi Jews

Pathophysiology

Hygiene hypothesis

Toll-like receptor mediated inappropriate immune response against gut bacteria

Epithelial barrier dysregulation

Intestinal vascular response - reduced blood supply in more chronic disease

50-70% Terminal ileum (TI)

Isolated colonic disease - 10%

Diffuse small bowel (SB) disease - 10%

<5% Gastroduodenal

Extraintestinal disease in 15-30%

Gallstones due to bile acid malabsorption 15-30%

Renal stones due to Vit D + Ca malabsorption 5-10%

Uveitis, iritis, episcleritis

Erythema nodosum, Pyoderma Gangrenosum

Primary sclerosing cholangitis, Pancreatitis

Venous thromboembolism

Genetics

15% have family history

50% concordance in monozygotic twins

IBD1 gene - codes for NOD2 - mutations more common in Crohn’s disease (CD) patients

CARD15 mutations in 40% CD patients

Associations

Turner syndrome

History and Examination

Perianal disease

Stool frequency, consistency

Vomiting

Anaemia

Clubbing

Mouth ulcers

Growth restriction due to malnutrition

Tender right lower quadrant

Look for cutaneuous fistulae

Stool/flatus/foaming/bleeding per urethra/vagina

Investigations

Upper and lower endoscopy + biopsies

Anti-saccharomyces cerevisae ASCA + pANCA abnormal in >95%

Stool culture, ova and parasites

Faecal calprotectin for diagnosis and monitoring

ESPGHAN Porto criteria for IBD in Paediatrics - scoring on history, exam, bloods, endoscopy/biopsy + SB MRI - expected +ve and -ve features

Histology

Non-caseating granulomas pathognomonic of CD - found in 20-30%

Radiology

AXR - bowel thickening, thumb printing (colonic wall thickening), pneumoperitoneum

USS - TI thickening, abscess, enlarged mesenteric lymph nodes

SB MRI for stricture, fistulae, abscess

CT with oral contrast for obstruction

Contrast enema - applecore strictures, cobblestoning, ulcers

Management

Aim for mucosal healing

6-8 weeks of elemental (liquid) diet e.g. Modulen - 50-80% remission rate after 4 weeks

Prednisolone if fails

Aminosalicylates for induction in mild disease

6-Mecaptopurine (6MP) + Azathioprine (AZA) are anti T-cell

Methotrexate is anti-inflammatory

Cyclosporin - IL2 inhibitor - reduces T cell response

Biologics (Infliximab) for induction and remission

Risks of sepsis, malignancy

Indications for surgery

Indications - failure on biologics e.g. antibody development

Chronic abdominal pain

Stricture (obstruction), fistula, bleeding, abscess

Growth restriction

Dysplasia/cancer

Stoma only in emergencies

If Indeterminate colitis - ileostomy until diagnosis established

Ileostomy in only severe refractory perianal disease

If perforated/active abscess - cannot have biologics. Requires MDT discussion, TPN, antibiotics, stoma for defunctioning

Most common procedure - ileocaecal resection

Keep margins <2cm as data shows no benefit to extended margins

Pass ureteric stent if inflamed retroperitoneum

Also will likely require future operations so bowel length preservation important

Stricturoplasty rarely necessary but used to preserve bowel length:

Heineke-Mickulicz strictureplasty (longitudinal incision, transverse closure) for short length (less than 10 cm) strictures

Finney strictureplasty (fold stricture, cut on side, side to side anastomosis) for medium length (10 to 20 cm) strictures

Michelassi strictureplasty (divide stricture, open along length, overlap and anastomose 2 ends) for long length (>20 cm) strictures

Fistulas should have direct repair

Bladders should be closed, leave catheter, cystogram in 2 weeks

Incidental appendicectomy - remove appendix only if base not involved, or leave alone and medically manage

If perforated - right hemicolectomy

Segmental colitis - segmental resection - or subtotal and ileorectal anastomosis without pouch

Rectal strictures can have serial dilatations

Anal fistulae do not follow Goodsalls rule in CD

Outcomes

TI disease recurrence 1/3

No increased complications if biologics given pre op

Risk of cancer, but moderate compared to UC - should have surveillance endoscopy every 10 years

Standard scenario

Adolescent with failing medical management of TI CD

Discuss in MDT with gastroenterologist, dietician

Delineate anatomy with SB MRI

If sealed perforation/fistula/small abscess - make nil enteral, start TPN and antibiotics

Once sepsis controlled, gastroenterologists can start Infliximab

If not controlled - ileostomy

If still symptomatic, repeat imaging and discuss in MDT with experienced IBD surgeon

Outcome may be to perform laparotomy

Ileocaecal resection and direct fistula repair - anastomosis if bowel condition favourable, stoma if not

References

Hirschl, Ron, et al., editors. "Crohn Disease." Pediatric Surgery NaT, American Pediatric Surgical Association, 2022. Pediatric Surgery Library, www.pedsurglibrary.com/apsa/view/Pediatric-Surgery-NaT/829045/all/Crohn_Disease.

Villanacci V, Reggiani-Bonetti L, Salviato T, Leoncini G, Cadei M, Albarello L, Caputo A, Aquilano MC, Battista S, Parente P. Histopathology of IBD Colitis. A practical approach from the pathologists of the Italian Group for the study of the gastrointestinal tract (GIPAD). Pathologica. 2021 Feb;113(1):39-53. doi: 10.32074/1591-951X-235. PMID: 33686309; PMCID: PMC8138698.

Levine A et al. European Society of Pediatric Gastroenterology, Hepatology, and Nutrition. ESPGHAN revised porto criteria for the diagnosis of inflammatory bowel disease in children and adolescents. J Pediatr Gastroenterol Nutr. 2014 Jun;58(6):795-806. doi: 10.1097/MPG.0000000000000239. PMID: 24231644.

Hesham W, Kann BR. Strictureplasty. Clin Colon Rectal Surg. 2013 Jun;26(2):80-3. doi: 10.1055/s-0033-1348045. PMID: 24436654; PMCID: PMC3709977.