Review article: quantitative leucocyte scanning in the assessment of inflammatory bowel disease activity and its response to therapy

Abstract

Inflammatory bowel disease (IBD) symptoms may be due not only to the effects of bowel inflammation, but also can result from many non-inflammatory consequences of the disease. Clinical scores and health questionnaire ratings produce a global assessment which is useful in the overall evaluation of the impact of the illness on the patient, and the effect of treatment. However many studies have failed to recognize the need to separately assess changes in the degree of bowel inflammation, in addition to a global clinical response. Radiolabelled white cell scanning using 111-indium has been shown to provide an accurate, quantitative and non-invasive method for assessing the degree of bowel inflammation in IBD and its response to therapy, using faecal collection or total body counts of radioactivity. More recently 99mTc hexamethyl propylene amine oxime (HMPAO) labelled white cell scanning has been introduced, which has advantages over the 111-indium method, including reduced radiation dosimetry and enhanced image quality. 99mTc-HMPAO scanning using three-dimensional white cell scanning (single photon emission computerized tomography; SPECT) allows visualization of the entire bowel separate from overlying structures. 99mTc-HMPAO white cell scanning with SPECT has now been computerized and automated to permit measurement of segmental and total bowel radiolabelled white cell infiltrate. This method could potentially provide the gold standard for objective assessment of the response of disease activity in Crohn's disease and ulcerative colitis, and merits application in clinical trials of novel therapies for IBD.