Equine Health Update EHU Vol 19 Issue 3 | Page 24

EQUINE | Proceedings instestinal surgery in horses. To an aggressive surgeon, any single indicator of intestinal strangulation makes a horse with colic a surgical candidate until proven other- wise. Conservative surgeons in the same situation prefer to wait until one or two additional physical parameters of strangulation support the initial assessment of intes- tinal hypoperfusion before committing to laparotomy. The exact effect of a brief delay in decision making, long enough to allow early signs of impending cardiovascu- lar shock to develop and support the choice for surgical intervention, is hard to quantify but certainly helps the decision-making process. Contraindications for surgical intervention are mostly clinical parameters indicative of enteritis. These include the absence of pain, the presence of depression, fever (> 102.5 F), neutrophilia or neutropenia and the presence of progressive intestinal sounds on auscultation. The absence of pain must however be interpreted with cau- tion. This is particularly true in cases of small intestinal obstruction where horses with bowel incarceration in internal hernias (in particular epiploic foramen entrap- ment and strangulating lipomas) can appear normal for a period of time after the initial episode of colic, until intestinal distension occurs oral to the obstruction and later become pain-free again when the bowel becomes necrotic and the horse becomes depressed due to en- dotoxaemia. In recent years, abdominal ultrasonography in particu- lar has proved complementary to the established clini- cal examination in evaluating bowel for distension, mu- ral thickness and motility. It has been mainly helpful in identifying small intestinal obstruction and was found to be more accurate than rectal palpation with a sen- sitivity of 98% and a specificity of 84% for small intes- tinal strangulating obstructions compared to 50% and 98% respectively for rectal examination (Klohnen et al. 1996). Ultrasonography from a ventral transabdominal window was also helpful in detecting increased large 24 colon wall thickness in horses with large colon torsion with a sensitivity of 67% and a specificity of 98% (Pease et al. 2004). Ultrasonography has further been reliable for the identification of nephrosplenic entrapment of the large colon, acquired inguinal or scrotal hernias and sand accumulations in the large colon. Current practice suggests that a technique referred to as FLASH (fast localized abdominal sonography of horses), a 7-site, 10-minute transabdominal ultrasound protocol for evaluation of the acute abdomen can be used by vet- erinarians without extensive ultrasound experience to detect major intra-abdominal abnormalities in horses with colic. Busoni et al (2011) showed that FLASH was able to show free abdominal fluid and abnormal intes- tinal loops. The positive and negative predictive values of the need for surgery of dilated turgid small intestinal loops using FLASH were 89% and 81%, respectively. Recent attention to blood plasma and peritoneal fluid lactate levels have indicated that these parameters can be used as prognostic indicators in horses with colic. One study established the BPL reference range as 0.59 + 0.22 mM and the PFL reference range as 0.49 + 0.27 mM. With each 1 mM increase in BPL or PFL, the respec- tive odds ratios for required abdominal surgery increase to 1.23 (BPL) and 1.58 (PFL), odds ratios for a required intestinal resection increase to 1.20 (BPL) and 1.41 (PFL), and odds ratios for developing ileus increase by 1.33 (BPL) and 1.36 (PFL). PFL concentrations of 1, 6, 12, and 16 mM corresponded to a probability of death of 11, 29, 63, and 82%, respectively, in horses without strangulat- ing obstruction and of 25, 52, 82, and 92%, respectively, in horses with strangulating obstruction (Delesalle et al. 2007). The physical examination should be as complete as pos- sible before administration of any diagnostic/therapeu- tic analgesic medication is considered. Important clini- cal signs may be masked by analgesic medication, the degree of which depends on the particular drug’s po- • Equine Health Update •