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EQUINE VETERINARY EDUCATION


Equine vet. Educ. (2020) 32 (8) 412-414 doi: 10.1111/eve.13070


Clinical Commentary Perplexing pedunculated lipomas


I. Kilcoyne and J. Nieto* Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California at Davis, Davis, California, USA *Corresponding author email: ikilcoyne@ucdavis.edu.


Keywords: horse; colic; strangulating; lipoma; surgery


Abdominal lipomas are benign smooth walled and encapsulated fat tumours that are formed by a hyperplastic growth of adipocytes originating from the mesenteric tissues of the small intestine and small colon in older horses (Archer 2007). Lipomas can occur as solitary masses, or alternatively multiple tumours can be found in the same horse. The small intestine has been reported to be involved in 89% and approximately 10% are associated with the small colon (Garcia-Seco et al. 2005). These lesions may be discovered as an incidental finding


at laparotomy or at necropsy examination, but often are implicated as a cause of colic due to their propensity to develop on a stalk associated with the intestinal mesentery of the small intestine or small colon. Strangulation of intestinal segments occurs when the stalk wraps around a segment of bowel resulting in luminal and vascular occlusion (Fig 1). Why some lipomas tend to lie dormant and some lead to severe intestinal incidents is not completely known or understood. Additionally, the length of the intestine that becomes entrapped by the lipoma can vary extensively. Factors such as the weight of the lipoma, length of the stalk and potential motility of the associated intestine could all be implicated (Edwards and Proudman 1994). Occasionally lipomas are found to be calcified or necrotic (Fig 2). Intestinal strangulation by a mesenteric lipoma is a


commonly encountered surgical lesion and it has been reported that pedunculated lipomas are responsible for up to 30% of all small intestinal strangulating lesions requiring surgery (Garcia-Seco et al. 2005). Lipomas are more commonly reported in older horses, with horses >15 years at increased risk (Edwards and Proudman 1994; Freeman and Schaeffer 2001; Garcia-Seco et al. 2005; Archer 2007). Garcia-Seco et al. (2005) reported a significant predisposition for Saddlebreds and Arabians to present with strangulating lipomas compared to other breeds. Other studies have reported Quarter Horses, Arabians, Morgans and ponies to be predisposed (Dart et al. 1992; Edwards and Proudman 1994). In the literature, it would appear that castrated males are over-represented compared to females or intact stallions (Blikslager et al. 1992; Garcia-Seco et al. 2005). It has been shown in small animals that neutering predisposes both dogs and cats to obesity and that this effect is due to behavioural changes such as reduced activity and increased food intake (Nguyen et al. 2004; German 2010). It is possible that a similar effect is seen in castrated male horses and it has been previously speculated that increased body weight may be a risk factor for the development of pedunculated lipomas (Edwards and Proudman 1994) in horses; however, to date this has not been confirmed. A recent study (Newkirk et al. 2014) looking at pituitary lesions, obesity and mesenteric


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lipomas in insulin resistant horses did have significantly more lipomas and higher lipoma area compared to insulin sensitive horses, although there was no correlation between body condition score (BCS) and lipoma frequency or total lipoma area. It is interesting to note that similar breed predispositions (Arabians, Saddlebred, Morgan and pony breeds) are affiliated with equine metabolic syndrome (Frank et al. 2010) and those presenting with lipomas. Although intestinal strangulation is the most common


surgical consequence of a pedunculated lipoma, the case report by Bauck et al. (2020) in this issue describes another manifestation of how a lipoma can induce colic. In the four cases (all greater than 20 years of age) described in this report, the mesentery appeared to have been strangulated by a lipoma, with the associated intestinal segment


Fig 1: Strangulating lipoma of the distal jejunum resulting in vascular and luminal obstruction of a section of jejunum.


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