Surgical management of portosystemic shunts

What is the pathophysiology behind PSS?

Abnormal communication

between portal and systemic

circulatory systems

What is a a vascular system that begins and ends in separate capillary beds?

portal system

What happens in a PSS?

liver

If there is a PSS, what would you see with regards ammonia, urea, protein, and nutrients?

- Ammonia high

- Low urea

- Decreased protein production

- Decreased nutrient absorption

What drains into the hepatic portal system?

Intestinal capillaries in the

intestinal villus drain

What is the MAIN purpose behind the portal system?

Allows for the absorption of a

product that can be directly

transported to a secondary site

What are the TWO types of shunts?

Portocaval, Portoazygous

Which one of the shunts can also arise from

the splenic vein, the gastroduodenal vein and the left gastric vein?

portocaval

What does a portocaval shunt connect?

portal vein and caudal vena cava

What does a portoasygous shunt connect?

azygous vein, portal vein

What type of CONGENITAL shunt is generally a SINGLE LARGE VESSEL and typically seen in small dogs?

Extrahepatic

What veins typically cause a extrahepatic shunt?

Portal vein, left gastric and splenic veins

What is the most common type of extrahepatic shunt?

Portocaval

What CONGENITAL shunt is seen in a SINGLE vessel in larger dogs?

Intrahepatic

What is occasionally seen in larger dogs that affects left side drainage?

Patent ductus venosus

What does an extrahepatic acquired shunts involve and where do you typically find them?

- MULTIPLE small vessels

- Highly concentrated around

kidneys

T/F Extrahepatic shunts are a natural "fail-safe: for portal hypertension

True

Is a acquired or congenital shunt more difficult to deal with?

acquired- it can only be medically managed

What is the signalment behind a congenital PSS is MOST common?

young Toy / small breeds animal

What are some large breed dogs that commonly have PSS?

Wolfhound, labs,

Australian cattle dog and

shepherd

What are some clinical signs of of a PSS?

- Small statue, "failure to thrive" / runt

• GI signs including vomiting, diarrhea, pica, melena (GI ulceration)

• Urinary issues can include, dysuria, polyuria, unable to housebreak, urate calculi (obstruction)

• Prolonged anesthetic episodes (neutering) Neurological signs

What is a common signs of PSS in cats?

Ptyalism (cats)

PSS in any young animal shows the following signs:

- Failure to grow (runt)

- Small size relative to litter mates

- Weight loss - failure to gain

What would you expect to see on urinalysis with an animal w a PSS?

- Specific gravity low (especially if BUN is low)

- May appear normal or even high in dehydrated, ill patient

- Ammonium biurate crystals or calculi

- Excretion of urates and ammonia instead of hepatic conversion to urea

dalmatian?

add later

You do a chem on a dog that you are 97% sure has a PSS based on the clinical signs. What do you expect to see on a chem panel?

- Low BUN

- Hypoproteinemia

- Low glucose

- Lower cholesterol

- Increased liver enzymes

Why do you see those chem results?

all of those things are produced in the liver so if that is screwed up then they also be screwed

What would you expect to see on CBC with PSS?

- Mild anemia

- Hypochromic, microcytic (defective iron transport or sequestration)

( - May see increased WBC but this is quite variable

- May indicate borderline sepsis)

What would you see on Urinalysis with PSS?

- Reduced urine specific gravity

- Urate crystalluria (ammonium biurate)

What is the prefered sample for a PSS testing?

Bile acids

What test needs immediate analysis; should be <100 mg/dl but needs to be shipped on ice if not done "in-house"?

Ammonia

If you are going to do an abdominal US to confirm PSS, what needs to be known?

the common locations of PSS

What can be helpful in ID the shunt?

Color flow "Doppler"

T/F Abdominal ulstrasound is considered a "non-invasive" procedure, but does typically require sedation

True

What is a minimally invasive surgery where you Administration of 99m technetium?

Scintigraphy

What would you expect to see on Scintigraphy if there is a shunt?

Shunt will have gap where liver should be and highlight the heart before the liver

What is an invasive procedure that uses a surgical technique for conformation and identification of the shunt vessel?

Portography

What are the TWO ways that you can do a Portography?

- Done in OR or immediately

before moving into

- Length of anesthesia and

hypothermia are real

concerns

What is the best for managing multiple, acquired shunts?

Medical management

What are some things associated with medical management of the PSS?

- Can treat condition chronically.

- Will always need medication and diet management

IF you choose to medically manage a PSS, what can disease this lead to?

liver damage leading to failure

T/F PSS is a surgical condition

True

If you surgically treat, what can lead to a normal life?

Complete occlusion

These are some things that you can do for medical management of a PSS?

- Low protein diet (Hill's l/d or similar)

• Decrease dietary load of proteins

• Watch owners giving treats; many treats /chew toys are

high protein (rawhide, hooves, ears, etc)

• Monitor for evidence of hypoglycemia

• Little hepatic reserve under conditions of stress or anorexia

• Lactulose

• Decrease colonic pH, change bacterial flora

• Decrease ammonia production and alters transmucosal

absorption

• Antibiotics

• Alter bacterial populations in colon

• Preference varies ... Results seem similar (neomycin,

Clavamox, metronidazole)

• H2 blockers

• Gastric ulcers from elevated gastrin levels

Patient has reduced hepatic metabolism with PSS. What do you need to make sure you pay attention to anesthesia/drug wise?

Watch doses of drugs requiring hepatic metabolism

What is the level of gas rates that can decrease portal blood flow, MAP and cardiac index

Gas rates >2x MAC

What is the BASICS behind PSS surgery?

• Complete abdominal exploratory

• Shunt vessel identification

• Isolation where shunt enters the systemic vessel

• Temporary occlusion

Where do you make the incision for PSS surgery?

Incision from xiphoid to pubis

What are the common entries for a shunt? (2)

• Caudal to the liver

• Cranial to the renal veins

Why is it important to isolate where the shunt enters the systemic vessels?

Prevents other contributing vessels from entering the shunt "down stream" from ligation

How do you preform Ameroid constrictor slow occlusion?

Hydroscopic material (casein) absorbs peritoneal fluid causing the casein to expand as it rehydrates

What does the expansion of the ameroid constrictor do?

This expansion compresses / occludes shunt vessel. The casein, is a "foreign protein" which causes a local inflammatory reaction. The inflammatory reaction contributes to vessel occlusion

You a little silly and start doing something and forget that there is a Ameroid constrictor on the shunt. What is the cause of this?

nothing there is minimal concern for portal hypertension

What is a sterilized 10-12 mm wide bands of cellophane material and what does it do?

Cellophane band, Isolate shunt vessel

How do you put in a Cellophane band surgically?

• Cellophane band is placed around the shunt vessel and tighten around the shunt.

• Secure band with vascular clips (stainless steel or titanium)

T/F You need to monitor cellophane bands for portal hypertension and the occulusion is typically slowed

True

The shunt should not be compresses by more than __%__ with an ameroid constrictor

25%

How do you want the ameroid constrictor to be positioned

want ameroid to be secure and

unable to twist when animal

returned to sternal position

You get a dog that comes in and on the sheet it says that it has surgery for a PSS. You take RADS and you see something that looks like a foreign body. The head surgeon head palms. Why did he do this?

the metallic band in place after ameroid placement after the PSS correction so it is not a gastric foreign body

What are some complications that can come from PSS surgery?

• Intraoperative hemorrhage

• Portal hypertension

• Seizures

T/F Tearing the shunt could result in catastrophic hemorrhage or in portal hypertension

True

Why do you need to measure portal pressure?

Measure portal pressure to obtain baseline using water manometer or direct pressure monitoring unit

What are some consequences of portal hypertension?

- Direct portal pressure measurement rises

more than 8-10 cm H2O above baseline

- Decrease in CVP (>1 cm) or significant

drop in arterial pressure

- Engorgement of mesenteric vessels

- Increase peristaltic activity

- Blue-gray color to bowel and pancreas

How is the survivability of pt that have seizures after PSS surgery?

Poor survivability in these patients due

to costs and duration of management

• If managed, can survive

PSS seizures are not responsive to benzodiazepines requiring the use of CRI of ____ (or similar medications)

propofol

Continue medical management for at least __#__ month after surgery to give the slow-occlusion method a chance to work

one

What are FOUR post medical management things that you have to do after a month?

- Repeat diagnostic imaging as appropriate (US or CT-A)

- Re-evaluate biochemical panel Bile acids may remain "abnormal"

but should have improved.

- For monitoring, a single sample is OK.

- "Pre" sample should be normal or at least decreased

You should discontinue oral meds in a stepwise manner, what should be discontinued first?

ABs and Keppra

With Intravascular occlusion, you can use interventional techniques for occlusion of

___, portosystemic shunts

intrahepatic

T/F Intravascualr occlusions requires special

equipment and facilities for this procedure

True

What surgery do you do for Intravascular occlusion?

Place vascular stents in the

shunt and then place

thrombogenic coils within

the shunt to be held in the

shunt vessel by the stent