Echinococcosis

Epidemiology & Risk Factors

• Etiology: Echinococcus granulosus (cystic echinococcosis; most common) or E. multilocularis (alveolar echinococcosis).
• Hosts:
  • Definitive host: Dogs/canines.
  • Intermediate host: Sheep, cattle, goats.
  • Accidental intermediate host: Humans (ingestion of food/water contaminated w/ dog feces containing eggs).
• Risk Factors: Rural sheep-farming regions (Mediterranean, Middle East, South America, Central Asia, Australia).

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Clinical Features

• Latent for years/decades; usually asymptomatic until cyst grows large. c
• Hepatic involvement (~60-70%, right lobe > left):
  • RUQ dull discomfort/pain, hepatomegaly, palpable mass, abdominal distension.
  • Biliary compression -> jaundice, pruritus.
• Pulmonary involvement (~20-30%):
  • Cough, chest pain, hemoptysis, dyspnea.
• Cyst rupture:
  • Fever, urticaria, severe anaphylactic shock, and rapid intraperitoneal dissemination.

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Diagnosis

• Initial Test: RUQ Ultrasound (shows simple/complex fluid-filled cyst with daughter cysts, internal septations, or “hydatid sand”).
• Confirmatory Imaging: Abdominal CT (demonstrates well-defined, unilocular or multilocular cyst with “eggshell” wall calcification).
• Key Labs:
  • Eosinophilia (present in <50%, increased if cyst leaks).
  • IgG Serology (ELISA): Confirms diagnosis; high sensitivity/specificity.
• Contraindication: Percutaneous diagnostic aspiration/biopsy is strictly CONTRAINDICATED due to high risk of leakage -> anaphylaxis and peritoneal seeding.

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Differential Diagnostics

• Amebic Liver Abscess (Entamoeba histolytica):
  • Diff: Acute onset w/ high fever, travel history, “anchovy paste” fluid, no calcifications or daughter cysts; treat w/ Metronidazole + Paromomycin.
• Pyogenic Liver Abscess:
  • Diff: Sepsis signs (high fever, leukocytosis), history of cholangitis/diverticulitis, CT shows solitary/multiple hypodense ring-enhancing lesions; treat w/ Abx + drainage.
• Simple Hepatic Cyst:
  • Diff: Congenital, completely asymptomatic, incidental finding, thin-walled on US, no calcifications/internal daughter cysts, normal serology.
• Hepatic Hemangioma:
  • Diff: Most common benign liver tumor, peripheral nodular enhancement on dynamic CT, hyperechoic on US, no calcifications.

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Management

• Medical Therapy: Albendazole (antihelminthic; monotherapy for small/asymptomatic cysts < 5 cm or inoperable pts).
• Invasive Interventions (Always co-administered w/ Albendazole before and after to reduce recurrence/anaphylaxis):
  1. PAIR Procedure (Puncture, Aspiration, Injection of scolicidal agent [hypertonic saline/ethanol], Re-aspiration):
     • Indicated for symptomatic cysts > 5 cm, non-operable candidates, or failure of medical therapy.
  2. Surgical Resection (En-bloc cystectomy or partial hepatectomy):
     • Indicated for large, complex cysts w/ multiple daughter cysts, superficial cysts at high risk of rupture, or biliary tract involvement.

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Complications

• Anaphylactic shock (spontaneous or iatrogenic cyst rupture).
• Intraperitoneal or intrathoracic rupture -> secondary hydatidosis (multiple seedings).
• Cyst infection -> pyogenic liver abscess formation.
• Mass effect -> biliary obstruction, portal HTN, Budd-Chiari syndrome.