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et al. 2000) or using a stapling device (Gaughan and Hackett 1990). To facilitate caecal ligation the use of a natural rubber ligature with a self-retaining knot has been reported (Wiemer and Van der Veen 1999). Despite inherent contamination, good results have been achieved (Wiemer and Van der Veen 1999; Hubert et al. 2000; Gunnarsdottir et al. 2011). Partial intraluminal typhlectomy has been developed as alternative necessitating a right flank approach and resection of the last rib with the horse in left lateral recumbency (Huskamp et al. 2013). Since caecocaecal intussusception appears to have a slightly better prognosis for long-term survival (65–75%) than caecocolic intussusception (44–49%) (Martin et al. 1999; Bell and Textor 2010), and due to the different surgical techniques described, accurate differentiation between the two types of intussusception couldbe helpful. In compiling this retrospective case series, we
hypothesised that: 1) caecal intussusception is visible on abdominal ultrasound in the vast majority of cases; 2) ultrasonographic differentiation between caecocaecal and caecocolic intussusception is often possible; and 3) survival to hospital discharge following surgical management of caecal intussusception is good.
Materials and methods
Data collection The medical records of all horses presented to the Faculty of Veterinary Medicine, Ghent University, Belgium, for the period 2009–2013 were reviewed retrospectively to identify horses suffering from intussusception involving the caecum. Horses were only included in the study if a diagnosis of caecocaecal or caecocolic intussusception was made at surgery or necropsy. Data concerning age, breed, sex, clinical signs, ultrasonographic findings, definitive diagnosis (caecocaecal or
caecocolic intussusception) based on surgical or post-mortem findings, treatment and short-term survival (defined as survival to hospital discharge) were collected.
Ultrasound An Esaote MyLab 30 with a 3.5 MHz phased-array probe1 or a GE Vivid 7 Dimension with 2.5 MHz phased-array transducer2 were used to perform transabdominal ultrasound of the left, right and ventral abdomen at admittance of each colic horse presented to the clinic. All horses were examined after applying 70% ethanol to improve contact between the probe and the skin. None of the horses had to be clipped to acquire satisfactory images. In all colic horses, the same transabdominal ultrasound protocol was followed. The whole left, right and ventral abdomen was scanned, starting caudally and progressing towards the thorax. Examinations were performed by five different clinicians and all images were reviewed by the same experienced observer, who was not blinded for the age, breed, sex and clinical parameters of the horses.
Results
Study population In total, 3269 colic cases were admitted and received a full abdominal ultrasound during the 5-year study period, of which 60 (1.8%) were confirmed caecal intussusceptions. Twenty-six mares, 20 stallions and 14 geldings were included and breed distribution reflected the hospital population: 33
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Fig 1: Transverse section through a caecocaecal intussusception presents as a disorganised oedematous structure (arrowheads) consisting of congested caecal wall. Differentiation between intussusceptum and intussuscipiens is often difficult. Total penetration depth is 25 cm.
Warmblood horses, 6 Warmblood ponies, 5 Friesians, 2 draught horses, 2 Standardbreds, 2 Miniature horses, 2 Welsh ponies, 2 Oldenburgers, one Paint, one Fjord, one Shetland pony, one Thoroughbred and one Haflinger. The median age of the affected animals was 2 years and age ranged from 4 months to 23 years. However, in the age category of horses under 2 years, caecal intussusception represented almost 10% of the colic cases (27/282). Thirteen horses were presented with caecal intussusception in winter (21%), 11 in spring (18%), 12 in summer (20%) and 24 in autumn (40%). Almost 50% (29/60) of the cases occurred in the months November (11/60), December (9/60) and January (9/60).
Abdominal ultrasonography All horseswithconfirmed caecal intussusception (caecocaecal or caecocolic) had ultrasonographic abnormalities consistent with this diagnosis on examination. Caecocaecal intussusceptions resulted in an oedematous
structure, consisting of the congested intussuscepted caecal wall, surrounded by the thickened outer caecal wall, found in the right dorsal two-thirds of the abdomen (Fig 1). Clear differentiation between the intussusceptum and the intussuscipiens was not always possible. Often liquid (diarrhoea) content was visible in the more dorsal part of the caecum, which resulted in visualisation of oedematous mucosal folds of the caecal wall floating in this fluid (Fig 2). Differentiation from typhlitis was sometimes challenging. Caecocolic intussusceptions resulted in an abnormal
structure in the right cranioventral third of the abdomen. At this location, a typical concentric ring structure (target-like) was found on a transverse section (Fig 3). Often the outer intussuscipiens, with a normal, sometimes difficult to visualise wall, was separated from the thick-walled, oedematous inner intussusceptum by a small interposed layer of hypoechoic or echogenic intestinal fluid. Sometimes one or both caecal taeniae could be visualised as an echogenic structure in the centre of the intussusception together with some hypoechoic abdominal fluid (Fig 3). On longitudinal section, the caecal apex was occasionally visible in the colon, surrounded by intestinal fluid (Fig 4). In four cases, the ring structure was
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