Fluorescein endoscopy

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Abstract
Late diagnosis contributes significantly to the mortality and morbidity of mesenteric ischemia. Although flexible endoscopy permits noninvasive assessment of the colon, ischemic colitis is often difficult to differentiate from nonspecific proctitis/colitis or mucosal changes seen in inflammatory bowel diseases. Intravenously administered fluorescein sodium (FSC) has long been used intraoperatively to assess bowel viability because its uptake is inversely proportional to the degree of intestinal ischemia. The authors wished to determine if FSC could be used to augment conventional endoscopy in an attempt to identify and monitor ischemic areas of the bowel within reach of the endoscope. Segmental mesenteric ligation of canine rectum was performed, and serial transanal biopsies obtained. Endoscopy was performed after intravenous FSC administration, using a rigid proctoscope, with a long-wave ultraviolet light source inserted into the lumen of the scope. Areas of nonspecific-appearing proctitis did not take up FSC and were easily differentiated from well-perfused areas by their failure to fluoresce. Ischemic areas were monitored in this manner over a 28-day period. Complete resolution of ischemic mucosal changes occurred with late stricture formation. In humans, the sigmoid and left colon are the areas most frequently affected by ischemic colitis. Because long-wave ultraviolet light is not transmitted through glass fibers, a different light source was needed for potential clinical application. To this end, a single fiber of an argon laser was inserted through the instrument channel of a colonoscope, resulting in greater fluorescence than seen with the ultraviolet light. FSC endoscopy appears to be a sensitive and accurate method of detecting and monitoring ischemic colitis and has many potential clinical applications.

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