EQUINE VETERINARY EDUCATION / AE / MAY 2018


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Aerobic and anaerobic bacterial culture done at the


Wemmershoek Diagnostic Laboratory revealed a pure culture of Streptococcus viridans, an isolate that is commonly associated with the normal gastrointestinal flora of horses (McVey et al. 2013).


Discussion


While ingestion of foreign bodies by horses is infrequent (in comparison to ruminants), when it does occur, it can often have disastrous implications. Most frequently ingested foreign materials include such things as pieces of fencing, hay nets, parts of feed bags, plastic bags or ropes, and also small wires from the inside of tractor tyres that are used as feed bins (Pusterla et al. 2006; Farr et al. 2010). These ingested particles can pass through the alimentary tract and become coated in a mineral precipitate and eventually cause a small colon impaction (Rosso et al. 2012) or obstruction (Dobson and Lopez 1981). Alternatively, the foreign body may migrate through the gastrointestinal wall at any point, and thereafter lodge in an extraintestinal site, where an abscess will form (Pusterla et al. 2007). This can lead to local inflammation, peritonitis, abscess formation or adhesions. These frequently cause acute abdominal pain, either due to small colon obstruction, or from perforation of the intestinal wall (Schumacher 2000) and subsequent peritonitis or abscessation with associated signs of chronic colic or weight loss (Spier et al. 1986). There are many descriptions in the literature of metallic


foreign bodies that either lodge in the upper alimentary tract (Baum et al. 1998; Pusterla et al. 2006), or perforate intestinal walls leading to acute colic, or chronic weight loss and depression (Saulez et al. 2009; Magri et al. 2010). Reports of abscesses formed around wires located within the liver and spleen (Rosso et al. 2012), in the jejunal mesentery (Davies 1983), and adjacent to the diaphragm or in the thorax (Tremaine et al. 1995; Monteiro et al. 2011) have all been published. In all published cases, the horses presented for acute colic signs, or for pyrexia, depression and weight loss (Rumbaugh et al. 1978; Dobson and Lopez 1981; Saulez et al. 2009; Lohmann et al. 2010). In this case, it is assumed that the metallic foreign body


migrated through the intestinal wall; however, no evidence of the migratory tract was obvious at post-mortem examination, though a small migratory tract could easily have been missed due to the presence of fibrous adhesions around the affected ovary. Intestinal source of the wire could be from the caecum, pelvic flexure, small colon or even jejunal loops. There was also no evidence of an external wound that would indicate a transcutaneous migration, but this could not be ruled out. Migration through the uterus could also have been a possibility, potentially migrating up the uterine horn during a previous breeding incident. The foreign body lodged itself within the stroma of the right ovary, and was subsequently encapsulated by the body, forming a large abscess. No colic signs were noticed by the owner at any stage, and the horse showed no overt signs of systemic illness at the time of presentation. The mare had failed to get into foal during the previous breeding season, but the enlarged ovary was only noticed by the referring clinician on routine palpation towards the end of the breeding season. The metallic foreign body had been fully encapsulated, and while adhesions had formed around the large abscess, there was no other


macroscopic evidence of peritonitis or local inflammation. As no evidence of a migratory or fistulous tract was located on post-mortem examination, the source of the metallic foreign body is unknown. Transrectal ultrasound findings were consistent with


abscessation, as gas was detected within the ovarian mass. This is not consistent with a granulosa cell tumour which usually has a honeycomb appearance with or without cystic structures. In addition to this, the mare did not show clinical signs consistent with granulosa cell tumour, namely behavioural changes such as aggressiveness and stallion-like behaviour (Hinrichs and Hunt 1990). Hormone level testing would have been useful in ruling out an ovarian tumour as increases in testosterone and inhibin levels is diagnostic in approximately 95% of granulosa cell tumours (McCue et al. 2006), and anti-M€


ullerian hormone in approximately 98% of


cases (Ball et al. 2013). It was deemed unnecessary in this case due to the suspicion of an ovarian abscess. Transcutaneous abdominal


ultrasound and


abdominocentesis cytology as well as ovarian centesis could potentially have provided a more comprehensive clinical picture preoperatively, and would have given an indication if a subclinical peritonitis was present, although it would probably not have changed the clinical outcome of the case, as laparoscopic evaluation of the extent and nature of the adhesions would still have been required. It has also been reported that the sensitivity of cytological analysis of the abdominal fluid in predicting the presence of an abdominal abscess is only about 40% (Zicker et al. 1998; Arnold and Chaffin 2012). During the laparoscopic procedure, an attempt was


made to break down the fibrous adhesions between the ovary and the body wall; however, tearing of the ovarian capsule with rupture of the abscess and contamination of the abdominal cavity with purulent material occurred. One of the risks of adhesiolysis during laparoscopic procedures is rupture of the viscus rather than the adhesion, and unfortunately that is what occurred in this case (Bleyaert et al. 1997). Early or fibrinous adhesions are easier to break


down, with fewer complications reported; however, mature, fibrous adhesions are tough, and breakdown of these adhesions often leads to tearing of the viscus (Bour


e et al.


2002). An alternative method of adhesiolysis such as use of a laser may have prevented this from occurring, but was unfortunately not available (Maier et al. 1992). The decision to subject the mare to euthanasia was


made with several considerations in mind; the purulent contamination of the abdomen and resulting septic peritonitis that would have resulted from this could have been treated with broad-spectrum antimicrobials and large volume peritoneal lavage, but financial implications would have been high. In addition to this, the nature and extent of the adhesions present would have necessitated the removal of most of the right horn of the uterus. While there are descriptions of successful partial ovariohysterectomy in horses (Berezowski 2002) and (Santschi et al. 1995) it is unknown to what extent the uterine horn can be removed and still result in pregnancy. There are reports of successful pregnancies after removal of 50% of one horn (Berezowski 2002), but in this case, more than 80% of the right horn would have had to be removed, and adhesions broken down from the uterine body. It was considered unlikely that such a procedure would result in a fertile reproductive tract. Had the mare been a riding


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