Determining the proximal extent of ulcerative colitis: white cell scan correlates well with histological assessment.

Background: Assessing the extent of ulcerative colitis determines therapeutic strategies and provides prognostic information. Colonoscopy with mucosal biopsy is considered unsafe in patients with severe disease.
Aim: To assess the correlation between proximal extent of ulcerative colitis as determined by Technitium-99-m hexamethylpropylene amine oxime labelled leucocyte scan (white cell scan) with that determined by histological assessment.
Methods: One hundred and thirty-five patients, with histologically-confirmed ulcerative colitis, who had a white cell scan and histological assessment of colonic inflammation within 6 months of each other, during the years 1991-2004, were included. Overall agreement, quadratic-weighted kappa (kappa) and polychoric correlations (rho) were calculated to estimate the inter-rater reliability.
Results: The correlation between white cell scan and histological extent was excellent (kappa = 0.7 rho = 0.8). Macroscopic appearance on colonoscopy did not correlate as well with histological extent (kappa = 0.62 and rho = 0.67). White cell scans correlated significantly better in patients with extensive disease (P = 0.02). Colonoscopy predicted disease extent more accurately in patients with limited colitis (P = 0.002).
Conclusions: Proximal extent of ulcerative colitis determined by white cell scans correlates well with histological assessment especially in patients with more extensive disease. White cell scans offer a reasonable alternative to colonoscopy with mucosal biopsies in determining the proximal extent of colitis.