Surgical repair of portoazygos shunts in three dogs and short-term

Abstract

CASE HISTORIES: The medical records of three dogs, presenting to the surgery department at a tertiary private referral hospital (Cork, Republic of Ireland), were retrospectively reviewed. The patients presented for investigation of a 3-day history of progressive lethargy, decreased appetite and hindlimb weakness (Case 1); brachycephalic obstructive airway syndrome (BOAS) and the development of abnormal licking behaviours (Case 2); and a 2-month history of increased thirst with elevated alanine aminotransferase (ALT) activity in serum (Case 3). CLINICAL FINDINGS: Case 1 presented with tachycardia, hindlimb paraparesis and neck pain, while Case 2 presented with facial conformation abnormalities consistent with BOAS. General physical examination and neurological assessment were within normal limits for Case 3. Baseline serum biochemistry measurements, in all three patients, indicated elevated activities of ALT and alkaline phosphatase, as well as elevated concentrations of resting bile acids (BA), suggestive of an extrahepatic portosystemic shunt. Abdominal computed tomography (CT) angiography was performed for each dog, which revealed the presence of a portoazygos shunt (PAS) with final insertion into the caudal azygos vein within the thorax. TREATMENT AND OUTCOME: Abdominal CT angiography images were used for surgical planning and a right-sided intercostal thoracotomy was performed. The location of the thoracotomy was patient-specific and located cranial to the diaphragm, either at the point of PAS insertion into the azygos vein or one rib-space caudal to the insertion, as determined by pre-operative CT images. The intercostal thoracotomy provided good visualisation of the PAS and an appropriate surgical field for placement of a thin film band around the PAS. No surgical complications or post-attenuation seizures were observed. All patients appeared comfortable on oral analgesia and were discharged from the hospital by 48 hours after surgery. All patients demonstrated a clinical improvement when reassessed 6-8 weeks after surgery, and Cases 2 and 3 demonstrated a reduction of resting BA concentrations to within normal limits. The third patient (Case 1) had a considerable reduction in the concentration of resting BA from >140 µmol/L to 20 µmol/L (reference range 0-10 µmol/L) 6-8 weeks after surgery. CLINICAL RELEVANCE: A right-sided intercostal thoracotomy can be considered for surgical management of PAS in dogs. While both intraoperative and short-term results appear promising, further prospective studies are required before this approach can be recommended as the preferred approach for PAS attenuation.ALP: Alkaline phosphatase; ALT: Alanine aminotransferase; BA: Bile acids; BOAS: Brachycephalic obstructive airway syndrome; CBC: Complete blood count; CT: Computed tomography; EHPSS: Extrahepatic portosystemic shunt; GLDH: Glutamate dehydrogenase; PAS: Portoazygos shunt.