High bile acids in a healthy Cairn: microvascular dysplasia or shunt
2-year-old male Cairn Terrier with no clinical signs. Pre-castration blood tests show high bile acids. There is no microcytosis, ammonium urate crystalluria or hypoalbuminaemia. Abdominal ultrasound by an experienced sonographer shows no anomalous vessel.
| Parameter | Result | Reference |
|---|---|---|
| Pre-prandial bile acids | 18 µmol/L | < 10 |
| Postprandial bile acids | 85 µmol/L | < 25 |
| Albumin | 3.2 g/dL | 2.6–4.0 |
| Cholesterol | 210 mg/dL | 135–345 |
| Protein C activity | 95% | 70–140 |
Which interpretation and plan are most appropriate?
chevron_right Show answer and explanation
A. Likely congenital shunt: CT angiography and ameroid constrictor
Dogs with congenital shunts usually have protein C activity < 70%, clinical signs, microcytosis or low urea and cholesterol. Here everything points to portal vein hypoplasia without portal hypertension, which is not surgically correctable.
B. Portal vein hypoplasia (microvascular dysplasia): monitor only
Correct. This is an abnormality of the intrahepatic portal branches, common in small-breed terriers and usually clinically silent. Protein C ≥ 70% distinguishes it from a congenital shunt, in which it is usually < 70%. No treatment is needed: inform the owner that bile acids will always be high and re-evaluate if signs develop.
C. Liver biopsy to distinguish shunt from dysplasia histologically
Liver histology is the same in both conditions (portal branch hypoplasia, arteriolar proliferation): biopsy cannot differentiate a congenital shunt from microvascular dysplasia.
D. Lifelong protein-restricted diet and lactulose as prevention
In an asymptomatic dog without encephalopathy, protein restriction is not indicated and may promote loss of muscle mass.
lightbulb Key takeaway
In small terriers with high bile acids and no signs, primary portal vein hypoplasia (microvascular dysplasia) is common. Protein C ≥ 70%, absence of signs and imaging without an anomalous vessel support it; biopsy cannot distinguish shunt from dysplasia.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.