Inaccuracy of serum bile acids to predict closure after surgical attenuation of a portosystemic shunt

Intercostal thoracotomy for surgical attenuation of portoazygos extrahepatic portosystemic shunts in three dogs: surgical technique and short-term outcomes

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 and the development of abnormal licking behaviours (Case 2); and a 2-month history of increased thirst with elevated alanine aminotransferase 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 brachycephalic obstructive airway syndrome. 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 alanine aminotransferase 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 portoazygous 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.

Liver function tests in dogs with congenital portosystemic shunts and their potential to determine persistent shunting after surgical attenuation

Portosystemic shunts (PSS) are congenital or acquired vascular anomalies that cause blood to bypass the liver. Liver function tests, such as fasting ammonia, ammonia tolerance test, and (paired) serum bile acids, are reliable for the diagnosis of PSS in dogs. Surgical attenuation is a common treatment for congenital PSS. Following surgical attenuation, it is useful to evaluate shunt closure. In this critical review, the ability of liver function tests to determine the presence and degree of residual shunting following surgical attenuation of canine PSS is discussed. Despite the availability of several liver function tests, a single rapid, simple, cost-effective, sensitive and specific test to evaluate surgical attenuation of PSS is not available.

Diagnostic value of blood variables following attenuation of congenital extrahepatic portosystemic shunt in dogs

BACKGROUND

The aims of this study were to determine if extrahepatic portosystemic shunt (EHPSS) postoperative closure could be predicted based on preoperative blood analyses and to determine the accuracy of blood variables to evaluate persistence of portosystemic shunting postoperatively (multiple acquired portosystemic shunts (MAPSS) or persistent EHPSS).

METHODS

Retrospectively, 62 dogs treated surgically for congenital EHPSS that underwent postoperative trans-splenic portal scintigraphy or CT angiography three to six months postoperatively were included.

RESULTS

None of the studied preoperative blood variables could unambiguously predict surgical outcome. Elevated postoperative fasting venous ammonia (FA) concentration always indicated surgical failure (persistent shunting or MAPSS), but normal FA did not provide any information on the postoperative shunting status. Paired serum bile acids (SBA) were not reliable enough to confirm or exclude postoperative shunting. In the presence of low normal postoperative FA levels, elevated preprandial SBA was more likely in dogs with persistent shunting (sensitivity of 0.79, specificity of 0.83), whereas postprandial SBA below reference limit was more often observed in case of surgical success (sensitivity of 0.93, specificity of 0.67).

CONCLUSION

Blood variables, and more specifically the combination of FA and SBA, are not a valuable alternative to advanced medical imaging to reliably assess the surgical outcome after EHPSS surgery.