Colour analysis of the equine endometrium: comparison of spectrophotometry and computer-assisted analysis of photographs within the L*a*b* colour space system.

The aims of this study were to compare two different methods of quantifying the colour of the luminal surface of the equine endometrium and to relate the results to histopathological evidence of inflammation and fibrosis. The mucosal surfaces of 17 equine uteri obtained from an abattoir were assessed using a spectrophotometer and by computer-assisted analysis of photographs. Values were converted into L()a()b(*) colour space. Although there was significant correlation between the two methods of quantification, variations in 'brightness', 'red' and 'yellow' values were noted. Within a given uterus, measurements using the spectrophotometer did not differ significantly. Using photographic analysis, brightness differed between horns, although no differences in chromaticity were found. Histopathological classification of changes within endometria corresponded to measured differences in colour. Extensive fibrosis was associated with increased brightness and decreased chromaticity using both methods. Inflammation correlated with reduced chromaticity, when measured by spectrophotometry, and with reduced brightness and yellow values, when assessed photographically. For this technique to gain wider acceptance as a diagnostic tool, e.g. for the endoscopic evaluation of uterine mucosae in vivo, standardised illumination techniques will be required so that colours can be compared and interpreted accurately.