Diffuse metastatic adenocarcinoma originating from the ovary in an Isa Brown chicken (Gallus gallus domesticus)

By Gary Fitzgerald BAppSc (VT), Cert IV Vet Nurse, VTS (Exotic Companion Animal), Certified ALS instructor (Recover), RVT coelomic neoplasia. 2: Dyspnoea of lower respiratory cause; differentials include: egg yolk coelomitis, fungal infections e.g. Aspergillus spp., bacterial pneumonia (Reavill, 2007). Diagnostic approach: The patient was admitted to hospital for a coelomic ultrasound and coelomocentesis. The ultrasound identified a large amount of free fluid and multiple ovoid/irregular-shaped structures with a combination of anechoic fluid and hypoechoic nodular structures. The patient was pre-oxygenated prior to the coelomocentesis with 100% O2 for 5 minutes prior and throughout the procedure via an anaesthetic mask. The skin of the ventral midline was aseptically prepared and a 20 g, 1-inch catheter was inserted into the coelomic cavity and stylet removed. A 50 cm extension set and threeway tap were attached, and using a 60 ml syringe, fluid was aspirated. A total of 440 ml of amber-coloured, slightly cloudy fluid was aspirated. The fluid was examined microscopically but was of low cellularity and was unremarkable. The patient’s respiratory effort returned to normal after the coelomocentesis with no further open mouth breathing. Treatment plan: The patient was dispensed meloxicam 2.8 mg (1 mg/ kg) PO 12H × 5d and scheduled for an exploratory celiotomy to differentiate yolk coelomitis vs neoplasia. Final diagnosis: The coelomic ultrasound identified a significant volume of free fluid within the coelomic cavity and multiple ovoid/irregularshaped structures with a combination of anechoic fluid and hypoechoic nodular structures indicating a yolk coelomitis or potential neoplasia, carcinomatosis, or lymphoma. As the respiratory symptoms returned to normal, post-coelomocentesis, it was presumed that these symptoms were associated with the coelomic effusion, compression and reduced tidal volume of the caudal and abdominal air sacs. Plans were made for a surgical exploratory celiotomy to differentiate yolk coelomitis vs neoplasia and to potentially perform a salpingohysterectomy if indicated.

Signalment: ‘Clarabelle’ – 4 year & 6-month-old female, Isa Brown chicken Presenting complaint: Dyspnoea with a distended coelom History: The patient was purchased from a local produce centre at the age of 3 months and had been kept in a large chicken coop with two other hens and a single rooster. All the chickens were fed a staple diet consisting of a complete chicken pellet, vegetable food scraps and occasionally a grain mix. The patient had not laid an egg since January 2018 and at the time of presentation had been dyspnoeic for the previous 24 hours with a distended coelom. Physical exam findings/Observations: On physical examination, the patient was bright, alert and responsive. Had a heart rate (HR) of 248 beats per minute (bpm) and respiratory rate (RR) of 60 breaths per minute with normal lung/ air sac and heart sounds. The eyes and nares were clear without discharge. The patient’s body weight was 2.76 kg with a body condition score assessed as good with a score of 3/5. The feathers and skin were normal with no evidence of external parasites. On palpation, the crop was empty and the coelom was moderately distended, and fluid filled. The patient’s respiratory effort was increased with a tail bob at each breath and intermittent open mouth breathing. Problem list/Differential diagnosis: The patient’s problem list included. 1: Coelomic effusion and distension; differentials include: yolk coelomitis,

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Outcome: The patient presented for surgery and was bright, alert and responsive. Blood was collected via basilic vein venipuncture and submitted to an internal laboratory for PCV, total protein (TP) and blood glucose analysis. The results of the PCV/TP (40%/48g/L) were within normal limits, but the blood glucose was mildly elevated at 24.1 mmol/L (12–17 mmol/L) indicating a stress-induced hyperglycaemia. A 22 g, 1-inch intravenous catheter was aseptically placed into the left medial metatarsal vein. Warmed Hartmann’s solution was started at 27.6 ml/hr (10 ml/ kg/hr). The patient was premedicated with methadone 1.38 mg (0.5 mg/kg) IV and midazolam 0.55 mg (0.2 mg/ kg) IV. The patient’s American Society of Anaesthesiologists (ASA) status was determined to be ASA III. Preoxygenation was administered with 100% oxygen via an anaesthetic mask for 10 minutes prior to induction. Anaesthesia was induced with sevoflurane in O2 (5%/2.0L/ min). The patient was intubated with a 4.0 mm uncuffed Murphy Eye endotracheal (ET) tube connected to a non-rebreathing circuit with a small animal ventilator and maintained on sevoflurane in O2 (1–3%/2.0L/min) for the anaesthetic duration. The patient was positioned in right lateral recumbency with the wings extended dorsally. A 24 g, 1-inch arterial catheter was aseptically placed in the left superficial ulna artery and connected to a transducer to monitor invasive blood pressure. Prior to the surgery, cephazolin 276 mg (100 mg/kg) IV was administered over 15 minutes. A fentanyl CRI (2–10 µg/kg/hr) IV was administered intraoperatively and titrated to effect. Throughout the anaesthetic and surgical procedure, the patient was monitored using capnography, pulse oximetry, ECG, invasive blood pressure, oesophageal temperature and physical parameters including HR and RR and corneal reflex. Immediately into the procedure the patient experienced an extreme hypotensive event, with mean arterial pressures (MAP) ranging between 35–45 mm Hg. The fentanyl CRI was increased to 13.8 µg/hr (5 µg/kg/hr) and the inhalant, isoflurane, was titrated down from 1. 75–1%. An anticholinergic was administered consisting of atropine 0.11 mg (0.04 mg/kg) IV with a crystalloid fluid bolus and Hartmann’s 27.6 ml (10 ml/kg) IV. This raised the MAP to above 40 mm Hg, but the patient was still hypotensive. At this point, a dopamine 27.6 µg/min (10 µg/kg/min) IV CRI was initiated, including a fresh frozen plasma (FFP) infusion 5.5 ml (2 ml/kg) IV in conjunction with a crystalloid over 30 minutes. This combined treatment resolved the hypotension and the patient’s MAP rose to above 70 mm Hg for the remainder of the procedure. As the surgery included incising through the left caudal and abdominal air sacs, the patient was manually ventilated, which removed the ability to monitor end tidal CO2 (ETCO2) during this period of the surgery. The feathers of the left lateral coelom were plucked, and the skin aseptically prepared for surgery. A linear incision was made in the left lateral flank extending from the caudal rib to the pubic bone through the superficial layers of muscles and air sacs. A Lone Star retractor was used to facilitate visualisation of the coelomic cavity. A yellow/brown gelatinous fluid was identified within the coelom and removed with suction. Digital exploration was performed through the peritoneum

Adenocarcinomas of the ovary or oviduct are a very common diagnosis of reproductive neoplasia in older chickens. A study addressing the cause of mortality in backyard chickens identified neoplasia as the most common cause of mortality, of which the most common non-virally induced neoplasms were ovarian adenocarcinoma and carcinomatosis

and mesentery identifying the presence of nodules throughout the coelomic cavity. Multiple ovarian cysts were present within the ovary ranging from 1 cm to 5 cm in diameter. Due to the presentation, the patient was diagnosed with diffuse metastatic adenocarcinoma. Due to the presence of diffuse carcinomatosis the owner elected for euthanasia, which was performed while under anaesthesia, and pentobarbitone sodium 977 mg (254 mg/kg) IV was administered. Conclusion/Case summary: Adenocarcinomas of the ovary or oviduct are a very common diagnosis of reproductive neoplasia in older chickens. A study addressing the cause of mortality in backyard chickens identified neoplasia as the most common cause of mortality, of which the most common non-virally induced neoplasms were ovarian adenocarcinoma and carcinomatosis (Cadmus et al., 2019). Ovarian neoplasia is often associated with secondary egg retention, ascites, cystic ovaries or oviductal impaction (Echols, 2015). Chickens with ovarian neoplasm often present for nonspecific symptoms such as coelomic distension, dyspnoea and ascites, lethargy and altered reproductive performance. Diagnostic imaging in the form of radiography, ultrasonography, computed tomography and magnetic resonance imaging can assist with a

non-invasive definitive diagnosis. More invasive techniques, such as exploratory coeliotomy, biopsy and endoscopy, are also used as diagnostic tools (Echols, 2015). Treatment should be aimed at the eradication of the tumour; this will often require multiple therapies concurrently. Surgical excision or debulking of the tumour, followed by chemotherapy or radiotherapy, can be used. Unfortunately, due to the ovary being associated with the aorta, total removal is virtually impossible (Filippich, 2004). Often, before an attempt can be made to surgically excise or debulk the tumour, treatment of secondary disease such as egg yolk coelomitis is required. This involves managing pain and inflammation with pure mu opioids and nonsteroidal anti-inflammatory drugs. Coelomic distension can be immediately treated with coelomocentesis to provide rapid relief. In the majority of cases, it is appropriate to remove as much of the coelomic effusion as possible to relieve respiratory compromise. Unfortunately, all cases have a poor prognosis unless complete surgical excision of the tumour is achieved (Echols, 2015). Mutations on the TP53 gene are thought to contribute to the development of ovarian carcinomas in chickens. Recent studies have been able to reduce the incidence of ovarian or oviductal cancer in chickens with the use of a trial chemoprevention therapy (Mocka et al., 2017). However, due to these tumours generally occurring towards the end of a chicken’s commercial lifetime, euthanasia is the general outcome (Cadmus et al., 2019; Tobias et al., 2011). Discussion: As the patient was dyspnoeic and had coelomic distension on physical exam, ultrasound was utilised as it could be performed on a conscious patient and would also assist a guided coelomocentesis to remove as much of the coelomic effusion as possible. Unfortunately, the ultrasound was unable to definitively diagnose ovarian carcinoma so an exploratory coeliotomy was performed. A significant challenge of this case was the hypotension experienced immediately after induction. Initial attempts to lower the inhalant requirement by increasing the constant rate infusion of fentanyl, a pure mu opioid, were unsuccessful. Initial fluid boluses to counteract the vasodilatory shock and administration of an anticholinergic were only mildly successful at increasing the patient’s blood pressure. Due to the extent of the hypotension, mean arterial blood pressure (MAP) of 40 mm Hg, the use of intravenous dopamine was instigated at a dose of 10 µg/kg/min concurrently with a natural colloid, fresh frozen plasma infusion. This aggressive treatment and the capability to monitor real-time invasive blood pressure via arterial catheterisation succeeded in raising the MAP to 70 mm Hg. Dopamine is commonly used in dogs and cats to treat severe hypotension but use in avian patients is poorly understood. Dopamine has direct activity at the β- and α-dopamine receptors dependent on dose. The dopaminergic effects predominating in low doses 1–3 µg/kg/min, the β- effects at moderate doses, 5– 10 µg/kg/min and the α- effects at higher doses > 15 µg/kg/min (Silverstein et al., 2015). Schnellbacher et al. (2012) examined the effects of dopamine on isofluraneinduced hypotension and found the dose rates of 7–10 µg/kg/min caused the greatest increase in arterial blood pressure in Hispaniolan Amazon parrots. Therefore, dopamine appears to be an appropriate treatment for severe hypertension in birds and potentially aided the restoration of normotension in this case. Another potential preventive may have been to induce general anaesthesia with an injectable agent. The high dose of inhalant anaesthesia required for mask induction is known to have a dose dependent vasodilation. This effect may have been mitigated by use of a shortacting injectable induction agent such as alfaxalone. Alfaxalone has minimal cardiovascular side effects when titrated to effect and is metabolised quickly. Due to the advanced nature of the diffuse carcinomatosis, it was unlikely that adequate debulking and surgical removal of the tumours could be performed and therefore a poor prognosis was determined even if followed up with chemo or radiotherapy. This resulted in the pragmatic decision to euthanise.

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