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Portosystemic shunts

image of Portosystemic shunts
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Abstract

Portosystemic shunts (PSS) are abnormal vascular communications between the portal venous system and the systemic venous circulation. This chapter considers anatomy, pathophysiology, anaesthesia, current techniques for intra- and extrahepatic shunts and postoperative management. Practical tips and warnings are highlighted throughout. Attenuation of an extrahepatic portosystemic shunt.

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Figures

Image of 10.1
10.1 Anatomical location of different types of portosystemic shunt.
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10.2 Common origins of extrahepatic shunts. The majority of extrahepatic shunts insert into the caudal vena cava (CdVC) between the right renal vein and the liver at the level of the epiploic foramen (arrowed). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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10.3 Congenital portoazygous shunt (arrowed) arising from the left gastric vein. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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10.4 Anatomy of intrahepatic shunts. (a) Right-divisional shunt. The portal vein (P) divides into a right and left branch. The right branch gives rise to a shunt that describes a loop (arrowed) before entering the right hepatic vein. (b) Central-divisional shunt. The portal vein (P) dilates before communicating with the caudal vena cava (CdVC) via a window-like ostium (arrowed). (c) Patent ductus venosus (left dorsolateral view). The portal vein (P) divides into a right (R) and left (L) branch. The ductus venosus (arrowed) arises from the terminal portion of the left branch and enters an ampulla before joining the left hepatic vein (LHV).
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10.7 Copper-coloured irises in a 9-month-old Domestic Shorthaired cat with an extrahepatic portosystemic shunt.
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10.11 Ameroid constrictor. The internal diameter of this constrictor is 5 mm, while the overall diameter is more than twice that, making the device bulky in small patients. A small round ‘key’ or cylinder of Ameroid clay is placed in the hole (arrowed) to secure the device once it has been positioned around a blood vessel.
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10.12 Intraoperative photograph of a central-divisional intrahepatic shunt. A Rummel tourniquet (white arrow) has been placed around the portal vein in preparation for portal venotomy and transvenous attenuation. Dilatation of the portal vein (*) indicates the point of origin of the intrahepatic shunt, although its course and its insertion into the systemic venous circulation are obscured by the hepatic parenchyma.
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10.13 Intraoperative photograph of transvenous attenuation of a central-divisional intrahepatic shunt. A portal venotomy has been performed in the dilated region of the portal vein from which the shunt is arising (yellow arrow). The window-like shunt (white arrow) can be seen deep inside the dilated segment. The opening of the left branch of the portal vein cannot be seen in this view but must be identified prior to placing the attenuating suture.
Image of Multiple acquired shunt vessels.
Multiple acquired shunt vessels. Multiple acquired shunt vessels.
Image of Identification of extrahepatic PSS. Ventral midline laparotomy view with the animal’s head towards the left of the photograph. The hepatic artery has been retracted using a Poole suction tip and a silk ligature placed around the shunt (white arrow) as it enters the caudal vena cava (CdVC).
Identification of extrahepatic PSS. Ventral midline laparotomy view with the animal’s head towards the left of the photograph. The hepatic artery has been retracted using a Poole suction tip and a silk ligature placed around the shunt (white arrow) as it enters the caudal vena cava (CdVC). Identification of extrahepatic PSS. Ventral midline laparotomy view with the animal’s head towards the left of the photograph. The hepatic artery has been retracted using a Poole suction tip and a silk ligature placed around the shunt (white arrow) as it enters the caudal vena cava (CdVC).
Image of Corrosion cast of the portal vasculature in a dog with an extraheptic shunt. Right lateral view with the dog’s head positioned towards the right. A silk ligature has been placed around the shunt between the left gastric vein (LG) and the caudal vena cava (CdVC). A well developed portal vein (PV) can be seen travelling towards the liver and arborizing into the different liver lobes.
Corrosion cast of the portal vasculature in a dog with an extraheptic shunt. Right lateral view with the dog’s head positioned towards the right. A silk ligature has been placed around the shunt between the left gastric vein (LG) and the caudal vena cava (CdVC). A well developed portal vein (PV) can be seen travelling towards the liver and arborizing into the different liver lobes. Corrosion cast of the portal vasculature in a dog with an extraheptic shunt. Right lateral view with the dog’s head positioned towards the right. A silk ligature has been placed around the shunt between the left gastric vein (LG) and the caudal vena cava (CdVC). A well developed portal vein (PV) can be seen travelling towards the liver and arborizing into the different liver lobes.
Image of Catheterized jejunal vein for portography or water manometry. (Courtesy of J Niles)
Catheterized jejunal vein for portography or water manometry. (Courtesy of J Niles) Catheterized jejunal vein for portography or water manometry. (Courtesy of J Niles)
Image of A shunt (arrowed) is identified between the portal vein (PV) and caudal vena cava (CdVC) at the level of the epiploic foramen.
A shunt (arrowed) is identified between the portal vein (PV) and caudal vena cava (CdVC) at the level of the epiploic foramen. A shunt (arrowed) is identified between the portal vein (PV) and caudal vena cava (CdVC) at the level of the epiploic foramen.
Image of The shunt is carefully dissected with Lahey bile duct forceps, close to its insertion into the caudal vena cava.
The shunt is carefully dissected with Lahey bile duct forceps, close to its insertion into the caudal vena cava. The shunt is carefully dissected with Lahey bile duct forceps, close to its insertion into the caudal vena cava.
Image of A 4 mm wide strip of cellophane, folded into three layers, is passed around the shunt.
A 4 mm wide strip of cellophane, folded into three layers, is passed around the shunt. A 4 mm wide strip of cellophane, folded into three layers, is passed around the shunt.
Image of The cellophane is tightened around the shunt and a stainless steel pin of predetermined diameter is secured using a surgical clip.
The cellophane is tightened around the shunt and a stainless steel pin of predetermined diameter is secured using a surgical clip. The cellophane is tightened around the shunt and a stainless steel pin of predetermined diameter is secured using a surgical clip.
Image of The stainless steel pin is withdrawn, allowing the shunt to expand to the diameter of the cellophane band. This causes partial immediate attenuation of the shunt without increasing portal pressure to dangerous levels. The cellophane band is trimmed close to the clip and manipulated into a position where it sits flat and does not distort or kink the shunt.
The stainless steel pin is withdrawn, allowing the shunt to expand to the diameter of the cellophane band. This causes partial immediate attenuation of the shunt without increasing portal pressure to dangerous levels. The cellophane band is trimmed close to the clip and manipulated into a position where it sits flat and does not distort or kink the shunt. The stainless steel pin is withdrawn, allowing the shunt to expand to the diameter of the cellophane band. This causes partial immediate attenuation of the shunt without increasing portal pressure to dangerous levels. The cellophane band is trimmed close to the clip and manipulated into a position where it sits flat and does not distort or kink the shunt.
Image of Portal venous pressure measurement using a water manometer connected to a catheter placed in a jejunal vein.
Portal venous pressure measurement using a water manometer connected to a catheter placed in a jejunal vein. Portal venous pressure measurement using a water manometer connected to a catheter placed in a jejunal vein.
Image of Intestines showing signs of portal hypertension. Note dark cyanotic colour, the dilated veins and hypersegmentation of the intestine.
Intestines showing signs of portal hypertension. Note dark cyanotic colour, the dilated veins and hypersegmentation of the intestine. Intestines showing signs of portal hypertension. Note dark cyanotic colour, the dilated veins and hypersegmentation of the intestine.
Image of Cellophane banding (arrowed) of a congenital extrahepatic shunt in a Maltese dog.
Cellophane banding (arrowed) of a congenital extrahepatic shunt in a Maltese dog. Cellophane banding (arrowed) of a congenital extrahepatic shunt in a Maltese dog.
Image of Placement of an Ameroid constrictor around a collapsed extrahepatic shunt vessel using Rummel tourniquets fashioned from 2 metric (3/0 USP) polypropylene and 18 G intravenous catheters. (Courtesy of J Niles)
Placement of an Ameroid constrictor around a collapsed extrahepatic shunt vessel using Rummel tourniquets fashioned from 2 metric (3/0 USP) polypropylene and 18 G intravenous catheters. (Courtesy of J Niles) Placement of an Ameroid constrictor around a collapsed extrahepatic shunt vessel using Rummel tourniquets fashioned from 2 metric (3/0 USP) polypropylene and 18 G intravenous catheters. (Courtesy of J Niles)
Image of Right-angled forceps being using to collapse the shunt vessel gently while the Ameroid constrictor is applied. (Courtesy of J Niles)
Right-angled forceps being using to collapse the shunt vessel gently while the Ameroid constrictor is applied. (Courtesy of J Niles) Right-angled forceps being using to collapse the shunt vessel gently while the Ameroid constrictor is applied. (Courtesy of J Niles)
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