FLASH SCANNING IN FIRST OPINION COLIC


of strangulating and other obstructions of the small intestine. Of the 34 horses with distended small intestine in the current study, 25 were euthanised without surgery due to clinical deterioration, 4 underwent surgery but did not survive, one underwent surgery and survived and only 4 recovered with medical treatment. The high euthanasia and non- survival rates in horses with this finding in the current study reflects the situation in first opinion practice, where euthanasia of horses with surgical intestinal lesions is often preferred by owners over surgical treatment (Averay et al., 2023 ). Older studies of colic indicated that severe forms of colic requir- ing surgery or euthanasia affected around 10% of cases seen in first opinion practice (Hillyer et al., 2001 ; Proudman, 1992 ; Tinker et al., 1997 ). However, a more recent study of colic cases exam- ined ‘out of hours’ in first opinion practice in the UK found that 23.5% of colic cases were considered ‘critical’, that is, required intensive medical or surgical treatment or euthanasia (Bowden, England, et al., 2020 ); a non- survival rate (including horses that were euthanased or died) of 19% was reported in the latter study. In the current study, 80 of 135 equids (59%) survived with medical therapy and 55 (41%) were either euthanised or died or underwent surgical treatment. Most of the horses that did not survive did not undergo a post- mortem examination, so the precise cause of colic in these animals was not determined. The age of the animals has been found to be a significant factor that influences owners ' atti- tudes towards consenting to surgery in horses with colic (Averay et al., 2023 ) and although the reasons why owners of animals eu- thanised in the current study opted for euthanasia were not re- corded, the authors believe that age and cost of surgery were the commonest contributory factors. However, age does not appear to affect the survival rate or rate of postoperative reflux in horses undergoing small intestinal surgery (Boorman et al., 2019 ). It is no- ticeable that the median age of animals that did not survive in this study (22 years) was significantly higher than the age of animals that survived (13 years). Several authors have reported that small intestinal wall thickness


of 3 mm or more is significant, which is the value we used in this study to report abnormal findings (Freeman et al., 2001 ; Klohnen et al., 1996 ; Le Jeune & Whitcomb, 2014 ). However, this finding was only weakly associated with non- survival in the current study due to the small number of cases. It should be recognised that small in- testinal wall increase in thickness can occur with a variety of other conditions such as enteritis, neoplasia and inflammatory bowel dis- ease (Freeman, 2002 ), in addition to small intestinal strangulations and obstructions. The commonest types of ultrasound scanners used to evaluate


the equine abdomen are those with a macro curvilinear low fre- quency (3–3.5 MHz) probe, that has a depth penetration of between 20 and 25 cm (Busoni et al., 2011 ; Klohnen, 2012 ). Although the im- ages obtained using higher frequency probes (>7.5 MHz) have greater definition, offering increased image clarity, they are only capable of imaging superficial structures and are not suitable to visualise the deeper regions of the gastrointestinal tract (Busoni et al., 2011 ). Five MHz linear probes (including transrectal transducers) can also be


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used, but they have a smaller window of imaging and do not have the same level of depth penetration as 3–3.5 MHz transducers; how- ever, in a recent study, transrectal transducers were demonstrated to be capable of imaging most of the abdominal organs transcutane- ously, but they failed to provide adequate detail of the left kidney and stomach (Haardt et al., 2021 ). In the current study, the wireless handheld ultrasound scanner with a 3.5 MHz curvilinear probe was found to be convenient, easy to use and effective at performing the FLASH procedure in the field in a wide range of different equine breeds. Such wireless scanners are light, portable and highly ma- noeuvrable; the absence of the cord that connects the transducer to the scanner in larger ultrasound systems was a definitive advan- tage when using the scanner in the field. Whilst the wireless scanner used in this study lacks the advanced imaging capabilities of larger ultrasound machines, for the purpose that it was being used (i.e. FLASH scanning of colic cases), the image quality was found to be adequate to provide the required diagnostic information. However, there were some animals where this scanner failed to produce diag- nostic images in certain windows, especially in obese animals and horses with long hair coats/caked in mud. The duodenal window, in particular, was found to be challenging to produce diagnostic images in all horses, and in some cases, this window was omitted in favour of the ventral abdominal areas where images of small intestine were more reliably detected. In the study by Busoni et al. ( 2011 ), five veterinary clinicians


without extensive experience of equine abdominal ultrasonog- raphy were trained in the FLASH technique for 1 h by an experi- enced radiologist prior to performing the procedure on 36 horses referred for colic. The FLASH scans were performed on both sides of the horses, and no horses were clipped. Although abdominal ultrasound scans can frequently be performed without clipping the hair (following soaking the hair and skin with surgical spirit/ isopropyl ethanol to facilitate coupling between the probe and the skin), it can be challenging to obtain good- quality images with- out clipping in some horses with long and thick haircoats or skin caked in mud, and in some ponies, donkeys and certain breeds with thick skin and heavy fat deposition (such as Friesians, draught breeds and Icelandic horses) (Cribb & Arryo, 2018 ; le Jeune & Whitcomb, 2014 ). Despite these challenges, the authors found that images good enough to complete the FLASH assessment were ob- tained in all of the animals in the current study. As with many diagnostic imaging procedures, the value of the


results is dependent on the skill of the operator, quality of image obtained and the experience of the clinician interpreting the find- ings (Southwood, 2023 ). Importantly, a negative finding or the sono- graphic findings deemed within normal limits, does not completely rule out a serious and life- threatening intestinal disease. Review articles by Fairburn ( 2017 ) and Waxman ( 2020 ) concluded that the main limitation of the FLASH technique is its inability to detect some conditions of the large intestines, such as the right dorsal displace- ment of the large colon. Although right dorsal displacement of the large colon was suspected in 11 horses in the current study, the di- agnosis was primarily based on the results of rectal palpation rather


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