Ultrasonographic Assessment of Small Intestinal Motility Following Hyoscine Butylbromide Administration in Horses

Background: Hyoscine butylbromide (HB) reduces intestinal motility. Horses commonly receive HB prior to hospital admission for colic; this could alter the appearance of the small intestine (SI) on ultrasound scan. 
Objectives: We hypothesised that HB-administration would lead to reduced SI-motility on ultrasonography as well as increased heart rate (HR). 
Study design: Prospective observational study. 
Methods: Client- owned horses were included with owner’s consent. Horses were hospitalised for medical colic and had normal baseline abdominal ultrasound examination. Ultrasonography was performed in three locations (right inguinal, left inguinal and hepatoduodenal window) before and 5, 10, 15, 30, 45, 60, 90 and 120 minutes after intravenous injection of 0.3 mg/kg HB. Video clips of 30 seconds duration were recorded. Three blinded reviewers assessed SI motility using a subjective grading scale: 1 = normal motility, 2 = reduced motility but loops contract fully down, 3 = reduced motility with incomplete contraction, 4 = no motility. Data were analysed with Friedman’s test and repeated measures one-way ANOVA. 
Results: Six horses were included. Hyoscine butylbromide did not lead to significant differences in SI-motility grade in any location (p = 0.6 left inguinal, p = 0.2 right inguinal, p = 0.09 duodenum). Some inter-individual and inter-observer variability was observed, but none of the included horses developed dilated turgid loops of SIs. Mean heart rate (± SD) was 33 ± 3 prior to HB-injection and peaked immediately at 71.33 ± 9 one-minute post-injection. Heart rate was significantly increased for 45 minutes following HB-administration (48 ± 9, p = 0.04). 
Main limitations: Small number of horses, inter- observer grading variability and lack of healthy control horses. 
Conclusions: The appearance of dilated turgid SI-loops common with strangulating intestinal lesions did not appear to develop following HB. Hyoscine butylbromide administered shortly before abdominal ultrasound examination would not be expected to affect clinical decision making. 
Ethical animal research: Approved by the RCVS Ethics Review Panel. 
Informed consent: Consent was obtained from owners of included horses. 
Competing interests: None declared. 
Sources of funding: None.

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