Updated: 12/21/2019

Amebic Liver Abscess

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  • A 38-year-old man presents to the emergency room for severe upper right quadrant (RUQ) pain for the past week. He describes a dull, 8/10 pain at the RUQ that is worse with breathing. He endorses fever, anorexia, and diaphoresis but denies steatorrhea, nausea/vomit, weight loss, or chest pain. He recently returned from Mexico following a work placement 5 weeks ago. A physical examination demonstrates hepatomegaly and point tenderness at the RUQ.
Introduction
  • Clinical definition
    • type of liver abscess caused by trophozoites of the parasite Entamoeba histolytica  
      • amebic liver abscess is the most common extraintestinal manifestation of amebiasis
    • amebiasis describes disease caused by E. histolytica and often affects the gastrointestinal system
      • most infections are asymptomatic
  • Epidemiology
    • demographics
      • more common in endemic areas which include India, Africa, Mexico, and parts of Central and South America
      • in developed countries, often seen in migrants from and travelers to endemic areas
      • more common among adult men
    • risk factors
      • immunosuppression
      • cancer
      • alcoholism
      • malnutrition
      • recent travel to endemic region
      • steroid use
      • pregnancy
  • Pathogenesis
    • humans are the principal host and reservoir of E. histolytica
    • transmission can occur fecal-orally, person-to-person, or sexually (oral-anal contact) 
      • commonly from consuming food or water that has been contaminated with feces
      • cysts of E. histolytica predominate in formed stools and allows for initial transmission/infection as it is resistant to gastric acid
    • once transmitted, cysts differentiate into its trophozoite form, which feed on bacteria and tissue, reproduce, and colonize the lumen and mucosa of the large intestine 
      • can also spread via the portal circulation to the liver, and rarely the lung, spleen, or brain resulting in metastatic abscesses
    • invasion of the liver most commonly involves the posterior part of the right side
      • abscess results from necrotic hepatocytes and is often described with an “anchovy paste” consistency containing aceullar, proteinaceous debris 
  • Associated conditions
    • amebic colitis
    • ameboma
    • pleuropulmonary infection
    • cardiac infection
    • brain abscess
    • cutaneous infection
Presentation
  • Symptoms 
    • RUQ pain  
    • cough
    • sweating
    • malaise
    • weight loss
    • anorexia
    • hiccup
    • diarrhea
  • Physical exam
    • fever
    • jaundice
    • hepatomegaly
    • RUQ tenderness
Studies
  • Diagnostic testing
    • diagnostic approach
      • diagnosis is primarily based on clinical presentation and confirmed via serologic or antigenic testing
    • imaging
      • ultrasound
        • best initial imaging
        • may demonstrate a cystic intrahepatic cavity with a round, well-defined hypoechoic mass
      • computed tomography (CT) 
        • best initial imaging
        • appears as a low-density mass with peripheral enhancing rim
      • magnetic resonance imaging (MRI)
        • low-signal intensity on T1-weighted images and high-signal intensity on T2-weighted images
    • studies
      • serology and antigen testing
        • confirms acute or previous infection
        • negative serology excludes the disease (though may be negative in the first seven days)
      • abscess aspiration
        • under ultrasound or CT guidance
        • rarely performed but indicated if the cyst appears to be at imminent risk of rupture
        • may visualize trophozoites
      • laboratory studies
        • increased ALP
Differential 
  • Pyogenic liver abscess
    • differentiating factors
      • abscess aspiration will yield bacterial organisms and polymorphonuclear cells
  • Echinococcal disease 
    • differentiating factors
      • will appear different on imaging (e.g., ground-glass appearance)
      • will have negative E. histolytica serology
  • Malignancy 
    • differentiating factors
      • rarely presents with RUQ pain and fever
      • can be differentiated via imaging and tissue biopsy  
Treatment
  • therapy can be initiated empirically based on clinical suspicion pending further diagnostic evaluation
  • First-line 
    • co-current use of a tissue and luminal agent for 7-10 days
    • tissue agents
      • e.g., metronidazole, tinidazole, and nitazoxanide
      • cure rate of > 90%
      • metronidazole is recommended in pregnant patients
    • luminal agents
      • e.g., paromomycin, diiodohydroxyquin, or diloxanide
      • elimination of intraluminal cysts even if stool microscopy is negative
  • Second-line
    • indicated in patients with relapse following therapy or slow response to therapy
    • therapeutic aspiration
    • percutaneous catheter drainage
    • prolonged course of metronidazole
Complications
  • Abscess rupture
  • Peritonitis
  • Hepatic vein or inferior vena cava thrombosis
 

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Questions (1)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
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