Surgical management of an extrahepatic portosystemic shunt in a foal: A multidisciplinary problem

Abstract

Summary A 5‐week‐old American Miniature filly was referred due to intermittent neurological signs of 4 weeks' duration. Clinicopathological findings showed increased ammonia and bile acids in venous blood samples. Abdominal ultrasonography detailed a portosystemic shunt (PSS). The foal underwent laparotomy and operative mesenteric portovenography, which further defined the PSS as extrahepatic portocaval in configuration. The PSS was occluded and intraoperative portovenography confirmed successful shunt occlusion. The foal made a good recovery from surgery and had a successful showing career until she succumbed to colic just over 3 years after surgery.

Computed tomography angiography of a congenital extrahepatic splenocaval shunt in a foal

“…Woodford et al [3] described the course of an extra-hepatic shunt in a foal, determined using ultrasonography and intra-operative fluoroscopy. Similar to the current case, this shunt coursed caudally and was located in the region of the renal veins.…”

“…Congenital portosystemic shunts have frequently been reported in small animals [1, 2] but are considered rare in foals. In the last 25 years only four cases of portosystemic shunts in foals have been described [3–5]. In two of those cases the shunt was extrahepatic.…”

“…The foal had grown to normal size and had shown no clinical diseaseAt 3 years of age subjected to euthanasia due to severe abdominal pain. Post mortem examination was not performed[3]Dutch Warmblood, male age 2 monthsEpisodes of apathy and ataxia, gnashing, circling, apparent blindness, depression, hypermetria alternated with dysmetria of all 4 limbs, bilateral horizontal nystagmus, ptosis, variable menace reflex and delayed correction reflexesBlood ammonia 117 µmol/L (11–55)Bile acid 53 μmol/L (1–8.6)Unconjugated bilirubin 168 μmol/L (< 35)CT angiography: abnormal vessel identified, looping from the portal vein to the caudal vena cava at the region. The abnormal vessel looped to the left and caudally, entering the left side of the caudal vena cava, just cranial to the left renal vein.…”

Portosystemic shunts: A diagnostic challenge

“…Definitive diagnosis of portosystemic shunts has been previously described in the literature including computed tomography angiography, mesenteric vein portography, splenic portography, transcolonic sodium pertechnetate Tc 99m scintigraphy and ultrasonography which was utilised in the case report by Woodford et al . () (Keane and Blackwell ; Wrigley et al . ; Buonanno et al .…”

“…The case report by Woodford et al . () discussed the use of a ligature to surgically correct an extrahepatic shunt. Since the foal was a miniature horse and 20 kg, the technique similar to dogs and cats could be utilised including a ventral midline approach.…”