Investigations

• FBC - anaemia due to blood loss; leukocytosis
  
  
• ESR - increased; correlates with active disease
  
  
• CRP - raised; but less so than in Crohn's disease
  
  
• biochemistry - in active disease, biochemical abnormalities may include hypokalaemia, hyponatraemia, hypomagnesaemia, hypocalcaemia, and hyoalbuminaemia. Abnormal LFTs due to associated chronic active hepatitis - increased ALT - or sclerosing cholangitis - increased alkaline phosphatase
  
  
• ANCA - found in HLA-DR2 associated form of ulcerative colitis
  
  
• radiology:
  • plain abdominal x-ray - excludes toxic dilatation, which is more than 5.5 cm in diameter in adults
  • barium enema:
    • diagnosis of extent and severity of the disease
    • procedure is contraindicated in those patients at risk of a toxic dilatation
      
      
• rectal biopsy - taken at sigmoidoscopy
  
  
• colonoscopy - this is contraindicated in those patients at risk of toxic dilatation. Allows multiple biopsies to be taken throughout the colon and delineation of the extent and activity of the disease
  
  
• white cell scan - allows imaging in severe disease
  
  
• molecular biology - a high intensity of CD44v6 and v3 epitope expression on crypt epithelial cells in patients with UC has been noted. This observation may have diagnostic potential in distinguishing UC from Crohn's

Reference

1. Rubin DT, Ananthakrishnan AN, Siegel CA, et al. ACG clinical guideline: ulcerative colitis in adults. Am J Gastroenterol. 2019 Mar;114(3):384-413.
2. Maaser C, Sturm A, Vavricka SR, et al. ECCO-ESGAR guideline for diagnostic assessment in IBD part 1: initial diagnosis, monitoring of known IBD, detection of complications. J Crohns Colitis. 2019 Feb 1;13(2):144-64.