Page 750 - Clinical Small Animal Internal Medicine

718 Section 7 Diseases of the Liver, Gallbladder, and Bile Ducts

Intrahepatic shunts were historically addressed by sur- cally significant problems with coagulation. This is much
VetBooks.ir gical attenuation using either extravascular dissection or more likely to be a problem in patients with end‐stage
liver disease.
a transvenous approach under partial venous inflow
The major life‐threatening complications that occur
occlusion. In recent years, minimally invasive proce-
dures have become more common, with an expanding perioperatively are portal hypertension and postligation
body of international experience in interventional tech- neurologic dysfunction. The incidence of portal hyper-
niques such as percutaneous thrombogenic coil emboli- tension has been greatly reduced by adoption of the slow
zation (PTCE). This technique results in much less occlusion techniques, and publication of guidelines for
morbidity. The downsides are the need for advanced safe shunt attenuation. Mild to moderate portal hyper-
equipment (including fluoroscopy) and expertise, and tension may not cause life‐threatening problems; affected
the likelihood that repeated procedures will be required patients may have inappetence or diarrhea for a short
for complete shunt occlusion (see Prognosis section). period of time, or develop ascites. Assuming they are
able to compensate hemodynamically for the reduced
Surgical Attenuation central venous return, and the bowel does not become
Surgical exploration is performed through a ventral critically hypoxic, they will eventually develop acquired
midline celiotomy, which may be extended cranially by shunts and a consequent return of portal pressure
transdiaphragmatic incision or median sternotomy. towards normal. Early published reports suggested that
Combination of a paracostal incision with a ventral mid- up to 20% of patients can be expected to develop acquired
line celiotomy is also an effective way of exposing the shunts but more recent studies, in which patients under-
craniodorsal abdomen, but is rarely required for shunt went postoperative evaluation using DPCTA, showed
surgery. A standard exploration should be performed to that the incidence is probably less than 10%, with an
evaluate the portal vasculature and identify the portosys- additional 10% of patients experiencing ongoing shunt-
temic shunt. If present, acquired shunts will usually be ing as a result of misplacement or failure of the attenuat-
visible around the cranial aspect of the left kidney. ing device to promote complete occlusion.
Postoperative neurologic sequelae range from blind-
Perioperative Monitoring and Treatment ness or muscle twitching, through disorientation, to
Serum glucose concentration should be monitored generalized motor seizures and status epilepticus.
regularly due to the tendency for hypoglycemia. Albumin Hypoglycemia and HE may also produce signs that can
levels may drop markedly when intravenous crystalloid be difficult to distinguish from true postligation neuro-
is administered at surgical rates, and plasma transfusion logic dysfunction . In addition, patients experiencing sei-
is sometimes required. However, serum albumin zures preoperatively may continue to have seizures
increases relatively little following plasma transfusion, postoperatively if the seizures were caused by something
and therefore human albumin solutions are an alterna- other than their CPS.
tively way to increase serum albumin. Hemodynamic Hypoglycemia, HE, and the seizures of idiopathic epi-
parameters should be measured regularly during and fol- lepsy should be manageable by evaluating the patient
lowing surgery to gauge trends and allow early detection and relevant bloodwork, and treating accordingly.
of developing portal hypertension. Patients can be Postligation neurologic dysfunction seizures and status
severely polyuric prior to surgery and may require epilepticus constitute a much more serious problem with
increased fluid rates to avoid dehydration postopera- a guarded prognosis. The cause of these seizures is still
tively. Potassium supplementation may be required. not well understood, but may include factors such as
imbalance of neurotransmitters, cerebral edema, and
Complications of Surgery derangements in cerebral blood flow. Historically, sei-
A large range of complications have been reported fol- zures were considered to occur acutely, with patients
lowing surgery for CPSS. Anesthetic‐related complica- found when they were already in status epilepticus.
tions include hypotension (mainly in cats), hypothermia Closer observation of patients following surgery has
due to small body size and poor body condition, and shown that in many cases, the condition is progressive.
hypoglycemia for reasons previously described. Patients start behaving abnormally, vocalizing and show-
Intraoperative hemorrhage is not usually a major issue ing signs of disorientation and inappropriate mentation.
unless tearing of the vessels occurs during dissection. They do not interact appropriately when being handled.
This is more likely during treatment of intrahepatic They are ataxic and often display compulsive move-
shunts, but unlikely if careful technique is used when ments. Left untreated, they will develop facial twitches
dissecting extrahepatic vessels. Although some pertur- that progress to generalized motor seizures and status
bations in coagulation parameters have been reported in epilepticus. Several studies have shown an incidence of
dogs with CPSS, most patients do not experience clini- seizures in up to 5% of dogs following surgery for CPSS.