Case Report a Colonic Epidermoid Cyst As a Cause of Chronic Recurrent Colic in a Horse A
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EQUINE VETERINARY EDUCATION / AE / APRIL 2007 123 Case Report A colonic epidermoid cyst as a cause of chronic recurrent colic in a horse A. BRÜNOTT*, V. KROEZE†, J. M. ENSINK, T. T. J. M. LAAN AND M. M. SLOET VAN OLDRUITENBORGH-OOSTERBAAN Department of Equine Sciences, Utrecht University, Yalelaan 12, 3584 CM Utrecht; and †Department of Pathobiology, Pathology Division, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, PO Box 80.158, 3508 TD Utrecht, The Netherlands. Keywords: horse; epidermoid cyst; horse; chronic recurrent colic Introduction pelvic flexure. The epidermoid cyst was located at the pelvic flexure and found to be attached to the right abdominal wall, Epidermoid cysts and dermoid cysts are well-circumscribed adjacent to the right inguinal ring. To our knowledge, the cystic structures and, when present, usually localised in the current report is the first to describe an epidermoid cyst in the dermis. An epidermoid cyst has a simple stratified squamous equine gastrointestinal tract. It suggests that, although epithelial lining, whereas the squamous epithelial lining of a relatively uncommon, infundibular cysts should not be dermoid cyst also contains adnexal structures (Hillyer et al. excluded in the differential diagnosis of chronic recurrent colic 2003). Overall, these (epi)dermoid cysts are uncommon in in the horse. horses, but when they occur, they usually present at the base of the ear, the false nostril (atheroma) or around the dorsal Case details midline of the horse (Hillyer et al. 2003). In these locations they do not usually cause pain. (Epi)dermoid cysts are History thought to be congenital and benign, but they may also be acquired secondary to trauma (Hillyer et al. 2003). A 3-year-old Quarter Horse breeding stallion was referred to Previous reports mention equine epidermoid cysts in the Department of Equine Sciences, Utrecht University, with a unusual locations. An intracranial epidermoid cyst in a horse history of chronic recurrent episodes of abdominal pain for the with neurological symptoms has been described by Peters previous 2 weeks. The episodes of colic lasted approximately et al. (2003); Camus et al. (1996) report an intraosseus 2 days and responded well to palliative treatment with NSAIDs epidermoid cyst in the mandible. In these cases the definitive and mineral oil. The horse had received adequate anthelmintic prophylaxis, had no history of eating disorders and there had diagnosis was reached following histological examination of the been no recent relevant changes in stable management. At excised masses, which revealed the typical histological features the time of referral, the horse had been showing mild to of epidermoid cysts: a well-circumscribed cystic structure with moderate signs of colic for 24 h. simple stratified squamous lining and filled with keratinous debris. However, no simple explanation was provided for the Clinical findings unusual extradermal location of these epidermoid cysts. In man, epidermoid cysts are known to have the At admission, the horse was in a moderate body condition potential to transform into squamous cell carcinoma (Hamlat (365 kg bwt). Respiratory rate was slightly elevated et al. 2005). In horses, no such transformation has been (24 breaths/min; reference range 8–14 breaths/min), but reported to date, although the epidermoid cyst described by heart rate (42 beats/min) and rectal temperature (37.6°C) Peters et al. (2003) displayed some histological signs of were close to, or within, the normal ranges (28–40 beats/min potential malignancy. and 37.4–38.0°C, respectively). No signs of dehydration Here we describe a horse suffering from chronic recurrent were present: the horse had pink mucous membranes, a colic caused by an epidermoid cyst in the wall of the colonic capillary refill time <1 s, warm extremities and a normal skin fold test. On both sides of the abdomen, gastrointestinal *Author to whom correspondence should be addressed. sounds were decreased in frequency. There were no signs of 124 EQUINE VETERINARY EDUCATION / AE / APRIL 2007 inguinal herniation. Nasogastric intubation produced 1 l of Surgery and post operative care gastric fluid. Rectal examination revealed a firm mass just cranial to the pelvic inlet, which on the basis of size, Prior to surgery, gentamicin3 (6.6 mg/kg bwt i.v.) and consistency and location, was suspected to be an impaction benzylpenicillin-sodium3 (106 iu i.v.) were administered via i.v. of the left ventral colon. In addition, the left ventral colon catheter in the right jugular vein. The horse was then sedated appeared to be attached to the abdominal wall adjacent to with detomidine (Domosedan)4 (10 µg/kg bwt i.v.), after the right inguinal ring. which general anaesthesia was induced with midazolam5 Haematology revealed a mild leucocytosis (10.9 x 109/l; (0.06 mg/kg bwt i.v.) and ketamine (Narketan)6 (2.2 mg/kg reference: 7–10 x 109/l) with a high percentage of segmented bwt i.v.). Thereafter, anaesthesia was maintained with neutrophils (85%; 35–60%), while PCV (0.40 l/l; 0.36–0.42 l/l) isoflurane-oxygen in a semi-closed circle system with assisted was not aberrant. Blood chemistry revealed total protein ventilation. The horse was positioned in dorsal recumbency level (71 g/l), and blood pH (7.44) to be within normal limits and a ventral midline laparotomy performed. (60–85 g/l and 7.35–7.45, respectively). Exploration of the abdominal cavity revealed a large, irregularly shaped mass (approximately 25 x 25 x 20 cm) Initial therapy originating from the wall of the pelvic flexure (Fig 1). The mass itself was attached to the left ventral abdominal wall next to The horse was treated with i.v. infusions of Ringer’s solution1 the right inguinal ring. A second paramedian laparotomy (grid (6 l in approximately 30 min), flunixin meglumine (Finadyne)2 incision) was made close to the right inguinal ring in order to (0.5 mg/kg bwt, i.v.) and mineral oil (1 l by nasogastric approach the mass. The mass was easily detached from the intubation). Over the next 3 days, the horse continued to abdominal wall by manual manipulation. The left ventral colon show mild signs of colic. On the third day following admission, with the mass was exteriorised through the midline incision, at clinical examination showed no abnormalities in breathing which time, a moderate impaction of the left ventral colon rate, pulse, and temperature, and haematological variables was also found to be present. had not changed since referral. Faecal production was normal. Proceeding to remove the mass, an enterotomy was first On repeated rectal examination the impaction of the left performed at the level of the pelvic flexure, followed by a ventral colon seemed to have softened, which was attributed thorough lavage of the left ventral colon. A side-to-side to the mineral oil treatment. However, the suspicion of an anastomosis was then created between the left ventral colon adhesion between the left ventral colon and the right and left dorsal colon by use of a linear cutter-stapling device abdominal wall still remained. (Proximate)7, and oversewn with a continuous Lembert suture To confirm this suspicion, a transrectal ultrasonographic pattern (poliglecaprone: Monocryl7 25, 3 metric). Resection of examination was performed. This revealed an irregularly the mass required removal of the entire pelvic flexure shaped, fluid-filled mass, in the right dorso-caudal part of the (approximately 50 cm of colon) including the enterotomy abdomen, to which the pelvic flexure was suspected to wound. Closure of the colon was performed as above. As adhere. repeated exploration of the abdominal cavity, gastrointestinal Based upon the clinical and ultrasonographic findings, a tract and abdominal wall revealed no further anomalies, both tentative diagnosis of an abscess or a neoplasm originating laparotomy wounds were then routinely closed. The mass from the pelvic flexure was made. Since the horse did not was sent to the Utrecht University Department of Veterinary respond well to the initial medicinal therapy, and adherence of Pathology. the colon to an intra-abdominal mass was suspected, it was Post operatively, the horse was treated with procaine decided that surgical intervention was necessary. penicillin G (Depocilline)9 (20 x 103 iu/kg bwt i.m. q. 24 h) Fig 1: Photograph of the macroscopic features of the mass, Fig 2: Photograph of the mass with its yellowish opaque attached to the pelvic flexure following enterotomy. seromucoid fluid contents. EQUINE VETERINARY EDUCATION / AE / APRIL 2007 125 and gentamicin3 (6.6 mg/kg i.v. q. 24 h) for 3 consecutive adhered to the colonic smooth muscle tunic (Fig 4). No days. Ten days after surgery the horse was discharged, and adnexal structures, such as hair follicles and glandular tissues, the owner advised to feed the horse small amounts of as seen in dermoid cysts, were associated with the present roughage several times daily. cyst. The inner lining of the cyst was composed of intact, well-differentiated cornifying stratified squamous epithelium. Pathology The epithelium was characterised by 1–2 layers of basal cells which consistently showed normal differentiation towards Grossly, a well circumscribed, smooth surfaced, fluctuant eosinophilic cornifying cells of approximately 10 cell layers cyst measuring approximately 25 x 25 x 20 cm was firmly thick ultimately covered by a broad layer of compact attached to the outside of the colonic pelvic flexure (Fig 1). orthokeratosis. Resembling an isthmus cyst, a granular There were no transmural communications with the lumen stratum was absent (Fig 5). These histological features are of the colon. On incision the cyst was unilocular and consistent with the diagnosis of an epidermoid cyst with an contained abundant yellowish opaque seromucoid fluid isthmus-like squamous differentiation. (Fig 2). No colonic luminal attenuation could be observed (Fig 3).