Centrifugation of peritoneal fluid improves visual assessment of strangulating lesions in equine colic

Background Early and accurate recognition of a strangulating lesion is essential to expedite surgical intervention in horses presenting with colic. Objective To evaluate the use of a colour grading scale in the visual assessment of peritoneal fluid, before and after centrifugation, and assess its ability to predict the presence of a strangulating lesion. Study Design Prospective clinical study. Methods Peritoneal fluid samples from 231 equids presenting with colic were visually analysed immediately after collection and assigned a numerical value based on a developed colour scale. Peritoneal fluid was centrifuged (4440 g for 3 min), and the visual assessment repeated. Clinicopathological data, lesion location/type, need for surgery and outcome were recorded. Logistic regression was used to outline associations between variables and the presence of a strangulating lesion. A receiver operating characteristic (ROC) curve was constructed to identify cut‐off values that correctly classified the highest percentage of strangulating and non‐strangulating lesions. Results Of the 231 equids included in the study 58 (25.1%) were diagnosed with a strangulating lesion. Using ROC analysis, the area under the curve (AUC) of the peritoneal fluid colour scale (i.e., 1–10), colour grade (i.e., yellow, orange or red) and transparency before centrifugation for the detection of strangulating lesion was 0.85, 0.82 and 0.74. After centrifugation the AUC of the peritoneal fluid colour scale, colour grade and transparency for the detection of strangulating lesion was 0.87, 0.84 and 0.55 (95% confidence interval [CI], 0.81–0.93, 0.78–0.89 and 0.5–0.6), respectively. Main Limitations Multiple observers analysed samples, which may have resulted in inaccurate reporting due to variances in colour perception. Confirmation bias may have influenced colour judgement as observers were not blinded to case details. A limited number of strangulating lesions were included. Conclusions Visual examination of peritoneal fluid colour following centrifugation is easy to perform and may be a distinguishing marker of ischaemia in equids presenting with strangulating lesions of the intestines.