Amebic Abscess

Question 1

What is the cause and locations

Answer 1

E. histolytica

is endemic in Mexico, India, Africa, and parts of Central and South America

Question 2

What might decrease the risk ?

Answer 2

menstruating women have a low incidence of invasive amebiasis

and pregnancy appears to abrogate this resistance.

Question 3

can someone who didnt travel have the disease ?

Answer 3

Patients with amebic liver abscess without a history of travel to an endemic area often have associated immunosuppression, such as human immunodeficiency virus (HIV) infection, malnutrition, chronic infection, or chronic steroid use

Question 4

Parthenogenesis

Answer 4

• Ingestion of E. histolytica cysts through a fecal-oral route
• Humans are the principal host, and the main source of infection is human contact with a cyst-passing carrier.
• Contaminated water and vegetables are also routes of human infection.
• Trophozoites reach the liver through the portal venous system
• The principal mechanism is probably enzymatic cellular hydrolysis.
• Early development associated with an accumulation of polymorphonuclear leukocytes, which are then lysed by the trophozoites.
• immunoglobulin A (IgA) antibodies have been shown to inhibit adherence to colonic epithelium invitro
  (((But doesnt stop preogression)))
• There is now evidence that a cell-mediated helper T-cell response is probably the major mechanism of resistance.

Question 5

Pathology

Answer 5

-abscess is essentially the result of liquefaction necrosis of the liver
-resembling anchovy sauce; the fluid is odorless unless secondary bacterial infection
-amebic abscesses tend to abut the liver capsule

capsule is resistant to hydrolysis by the amebae

Question 6

can it presents with colitis ?

Answer 6

Synchronous hepatic abscess is found in one third of patients with active amebic colitis.

Question 7

Most Common Findings in Labs ?

Answer 7

• The most common LFT abnormality is an elevated PT-INR.

Question 8

Most beneficial Lab test ?

Answer 8

• measurement of circulating antiamebic antibodies,

> An indirect hemagglutinin test sensitivity of 90%.
replaced by enzyme immunoassays
detect the presence of antibodies against the parasite
sensitivity of 99% and specificity higher than 90%

the presence of antibodies may reflect prior infection

Question 9

Xray findings ?

Answer 9

elevated right diaphragm
pleural effusion
atelectasis.

Question 10

US features ?

Answer 10

rounded lesion abutting the liver capsule without significant rim echoes, interpreted as an abscess wall.

The contents of the cavity are usually hypoechoic and nonhomogeneous

Question 11

How to be differentiated by CT ? from Pyogenic

Answer 11

rim enhancement noted in the pyogenic abscess

Question 12

What about nuclear medicine ? can also differentiate ?

Answer 12

gallium scanning or Tc 99m liver scans, can be helpful in differentiating pyogenic from amebic abscesses because

the amebic abscesses typically do not contain leukocytes and therefore do not light up on these scans

Question 13

if workup is still not definitive, what to do ?

Answer 13

-First, a therapeutic trial of antiamebic drugs
-Second option, a diagnostic aspiration, should be considered

Question 14

C/S difference

Answer 14

A pyogenic abscess would have bacteria and leukocytes, whereas an amebic abscess would contain the typical so-called anchovy sauce.

Cultures of amebic abscess are usually negative and do not contain leukocytes.

Question 15

When you should not Do Aspiration

Answer 15

In patients for whom neoplasm or hydatid disease is in the differential diagnosis, aspiration should not be performed

Question 16

Tx ?

Answer 16

• metronidazole (750 mg orally, three times daily for 10 days)
• Other nitroimidazoles (e.g., secnidazole, tinidazole)
• Emetine hydrochloride > requires intramuscular injections > serious cardiac side effects.
• chloroquine > less effective agent.
• After treatment of the liver abscess, it is recommended that luminal agents such as iodoquinol, paromomycin, and diloxanide furoate be administered to treat the carrier state

Question 17

When to Aspirate ???

Answer 17

• for diagnostic uncertainty
• Failure to respond to metronidazole therapy in 3 to 5 days
• Abscesses thought to be at high risk for rupture.

High Risk Rupture :
- Abscesses larger than 5 cm And in the left liver

Question 18

Outcomes/Complications ?

Answer 18

• The most frequent complication of amebic abscess is rupture into the peritoneum, pleural cavity, or pericardium

Question 19

Peritoneal Rupture Tx ?

Answer 19

• Most peritoneal ruptures tend to be contained by the diaphragm, abdominal wall, or omentum, but rupture can fistulize into a hollow viscus.
• treated successfully with percutaneous drainage.
• Laparotomy is indicated in cases of doubtful diagnosis, hollow viscus perforation, fistulization resulting in hemorrhage or sepsis, and failure of conservative therapy.

Question 20

Rupture into plural space Tx ?

Answer 20

• Rupture into the pleural space usually results in a large and rapidly accumulated effusion that collapses the involved lung.
• Treatment consists of thoracentesis

Question 21

rupture into the pericardium Tx ?

Answer 21

Rarely, a left-sided abscess may rupture into the pericardium and can be manifested as an asymptomatic pericardial effusion or even tamponade.

This must be treated with aspiration or drainage through a pericardial window.

Question 22

Other Complications

Answer 22

Other complications include compression of the biliary tree or IVC from a very large abscess and the development of a brain abscess.

Question 23

Mortality with Rupture ? , Factors with Poor Outcomes

Answer 23

When an abscess ruptures, mortality ranges from 6% to as high as 50%.

Factors independently associated with poor outcome:

-elevated serum bilirubin level (>3.5 mg/dL),
-encephalopathy
-hypoalbuminemia (<2.0 g/dL)
-multiple abscess cavities
-abscess volume larger than 500 mL
-anemia
-diabetes.