Chapter 18 –Circulatory Disorders :IMPAIRED BLOOD FLOW INTO THE LIVER

Question 1

Why are liver infarcts are rare?

Answer 1

thanks to the double blood supply to the liver

Question 2

So what is the reason for the occurence of localized infarct in the liver?

Answer 2

Nonetheless, thrombosis
or compressionof anintrahepatic branchof thehepatic artery by:

• embolism
• neoplasia,
• polyarteritis nodosa ( Chapter 11 ), or
• sepsis

may result in a localized infarct that is

usually anemic and pale tan, or sometimes hemorrhagic, as a result of suffusion of portal blood.

Question 3

Why is interruption of the main hepatic artery does not always produce ischemic necrosis of the organ,
particularly if the liver is otherwise normal?

Answer 3

Retrograde arterial flow through accessory vessels,
when coupled with the portal venous supply, is usually sufficient to sustain the liver parenchyma.

Question 4

Interruption of the main hepatic artery does not always produce ischemic necrosis of the organ,
particularly if the liver is otherwise normal.

What is the exception to this?

Answer 4

The one exception is hepatic artery thrombosis in a transplanted liver, which
generally leads to infarction of the major ducts of the biliary tree and loss of the organ

Question 5

Answer 5

FIGURE 18-36 Liver infarct. A thrombus is lodged in a peripheral branch of the hepatic
artery and compresses the adjacent portal vein; the distal hepatic tissue is pale, with a
hemorrhagic margin.

Question 6

What is the clinical course when there is blockage of the extrahepatic portal vein?

Answer 6

may be insidious and well tolerated, or may be a
catastrophic and potentially lethal event;

most cases fall somewhere in between.

Occlusive disease of the portal vein or its major radicles typically produces abdominal pain and, in most instances, other manifestations of portal hypertension, _principally esophageal varices that are
prone to rupture._

Ascites is not common (because the block is presinusoidal), but when present,
is often massive and intractable.

As discussed earlier, ascites is common in cirrhosis due to sinusoidal block and hyperdynamic circulation. Acute impairment of visceral blood flow leads to
profound congestion and bowel infarction.

Question 7

Why is ascites not common in blockage of the extrahepatic portal vein?

Answer 7

because the block is presinusoidal but when present,
is often massive and intractable.

Question 8

Extrahepatic portal vein obstruction may arise from the following conditions, but in about one
third of cases no cause can be implicated:

Answer 8

• Subclinical occlusion of the portal vein, from neonatal umbilical sepsis or umbilical vein catheterization, presents as variceal bleeding and ascites years later
• •Intra-abdominal sepsis, caused by acute diverticulitis or appendicitis leading to pylephlebitis in the splanchnic circulation
• Inherited or acquired hypercoagulable disorders, including postsurgical thromboses and myeloproliferative syndromes
• Trauma
• Pancreatitis and pancreatic cancer that initiate splenic vein thrombosis, which propagates into the portal vein
• Invasion of the portal vein by hepatocellular carcinoma
• Cirrhosis, which is associated with portal vein thrombosis in about 25% of patients with thrombosis

Question 9

Intrahepatic portal vein radicles may be obstructed by what?

Answer 9

acute thrombosis .

The thrombosis does
not cause ischemic infarctionbut insteadresults in a sharply demarcated area of red-blue
discoloration called infarct of Zahn.

There is no necrosis, only severe hepatocellular atrophy and marked hemostasis in distended sinusoids.

Invasion of the portal vein system by primary or
secondary cancer in the liver can progressively occlude portal inflow to the liver; tongues of
HCC can even occlude the extrahepatic portal vein

Question 10

What are Noncirrhotic Portal Fibrosis and Idiopathic Portal Hypertension?

Answer 10

These conditions are similar and characterized by portal hypertension and a moderate degree
of portal fibrosis without cirrhosis. [64]

Question 11

Noncirrhotic portal fibrosis is common in

Answer 11

India and
generally presents with upper gastrointestinal bleeding.

Question 12

What is Idiopathic portal hypertension?

Answer 12

• described in Japan,
• has a female predominance, and
• usually presents with splenomegaly.

Question 13

What is the pathogenesis of Noncirrhotic Portal Fibrosis and Idiopathic Portal Hypertension?

Answer 13

The pathogenesis of these conditions is unknown.

It has been proposed that they may result from
bacterial infectionof thegut causing septic embolization of the portal vein.

Another proposed
mechanism is the fibrosis of portal vein branches associated with the increased expression of
vascular cell adhesion molecule-1 (VCAM-1).

Question 14

What is the histological morphology ofNoncirrhotic Portal Fibrosis and Idiopathic Portal Hypertension?

Answer 14

​Histologically there is a variable involvement of
portal tracts,only some of which have increased connective tissue deposition and fibrosis.

In
addition, there is obliteration of small branches of the portal veins.

This histological picture is
sometimes referred to as hepatic sclerosis or obliterative portal venopathy.