Follow-up in Hepatic Alveolar Echinococcosis Under Benzimidazole Therapy Using Computed Tomography

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Follow-up in Hepatic Alveolar Echinococcosis Under Benzimidazole Therapy Using Computed Tomography

Alveolar echinococcosis (AE)—caused by the tapeworm Echinococcus multilocularis—is often called the “most dangerous parasitic zoonosis” in temperate regions of the Northern Hemisphere, including Central Europe and parts of North/Central Asia. Left untreated, it kills nearly all patients within 10–15 years. The liver is the most common target, with lesions that can be invasive, tumor-like, or cystic. When surgery isn’t an option, long-term benzimidazole drugs (like albendazole or mebendazole) are the standard: these medications slow parasite growth (a “parasitostatic” effect) instead of killing it, stopping the disease from spreading.

To understand how AE lesions change under this therapy, a team of researchers from Germany’s University Hospital Ulm and China’s Qinghai University Affiliated Hospital studied 72 patients using the E. multilocularis Ulm Classification for CT (EMUC-CT)—a system that categorizes liver lesions by shape (diffuse, tumor-like, cystic) to standardize diagnoses and track progress over time.

What the Study Examined

The team analyzed data from the German national AE database, focusing on patients who:

  • Had not undergone liver surgery for AE.
  • Took benzimidazoles continuously (albendazole: 10–15 mg/kg daily; mebendazole: 40–50 mg/kg daily).
  • Had two CT scans: an initial “baseline” scan and a follow-up scan (average 39.8 months later).

Using EMUC-CT, two independent readers evaluated:

  1. Lesion morphology (Type I: diffuse; Type II: tumor-like; Type IIIa/b: cystic; Type IV: small/metastasis-like; Type V: calcified).
  2. Calcification (a hallmark of AE, rated as none/slight/moderate/considerable).
  3. Lesion size (maximum width of the largest liver lesion).
  4. Number of lesions (total AE spots in the liver).

Key Findings

1. Lesion Shape Stays Stable

Under benzimidazole therapy, 98.6% of patients kept the same primary lesion type—meaning a diffuse Type I lesion didn’t suddenly become a tumor-like Type II. Only 1 patient’s lesion changed (from cystic Type IIIa to calcified Type V). This aligns with the drug’s parasitostatic effect: it stops the parasite from spreading, so the lesion’s basic structure remains intact.

Type I (“diffuse infiltrating”) was the most common (45.8% of patients), followed by Type II (20.8%), Type IIIa/b (18.0%), Type IV (14.0%), and Type V (1.4%).

2. Calcification Increases Over Time

Calcification is the body’s response to AE, and it’s a sign the parasite may be less active. The study found:

  • 16.7% of patients saw their calcification pattern become more prominent (e.g., from “feathery” to “diffuse” calcium buildup).
  • Overall calcification levels rose significantly:
    • Baseline: 6.9% no calcification, 40.3% slight, 33.3% moderate, 19.4% considerable.
    • Follow-up: 2.8% no calcification, 19.4% slight, 41.7% moderate, 36.1% considerable.

Past research links increasing calcification to lower parasite activity—a positive sign therapy is working.

3. Lesion Size Shrinks for Most Types

The average size of the largest lesion dropped from 86.2 mm to 80.9 mm (a statistically significant reduction, P < 0.0001). Breaking it down by type:

  • Type I (diffuse): Shrunk from 80.6 mm to 75.3 mm (P = 0.0092).
  • Type II (tumor-like): Shrunk from 110.9 mm to 105.4 mm (P = 0.0166).
  • Type IIIa/b (cystic): Shrunk from 113.4 mm to 104.2 mm (P = 0.0205).

Type IV (“small/metastasis-like”) lesions didn’t change size—likely because they’re already tiny. Type V (calcified) was too rare to analyze.

4. More Lesions = Smaller Lesions

An interesting pattern emerged: patients with more lesions had smaller individual lesions (a moderate-to-strong correlation, R² = 0.5744). This raises questions about AE growth—do multiple lesions compete for resources, keeping each other small?

Limitations

The study had constraints:

  • Small sample size: Only 72 patients, and Type V (calcified) lesions were almost nonexistent.
  • Subjective calcification ratings: Doctors judged “slight” vs. “moderate” calcification, which can vary.
  • Retrospective design: The team used existing data, so they couldn’t control variables like drug adherence.

What This Means for Patients

The findings confirm benzimidazoles work as intended: they stop disease progression and keep lesion shape stable. The increase in calcification suggests the parasite is less active, and shrinking lesions might even make surgery possible for patients who initially couldn’t undergo it.

For doctors, EMUC-CT is a powerful tool—since lesion shape stays consistent, it helps monitor therapy effectiveness without relying on single metrics (like size alone).

Who Conducted the Research?

The study was led by Dr. Tilmann Graeter (Department of Diagnostic and Interventional Radiology, University Hospital Ulm, Germany) and co-authored by researchers from:

  • University Hospital Ulm (Radiology, Internal Medicine, Pathology, Surgery, Infectious Diseases).
  • Qinghai University Affiliated Hospital (China).

It was funded by Germany’s Research Foundation (DFG) and published in the Chinese Medical Journal (2020, Volume 133, Issue 12).

Graeter T, Shi R, Bao HH, Kratzer W, Barth TF, Hillenbrand A, Henne-Bruns D, Schmidberger J, Gruener B, Li WX. Follow-up in hepatic alveolar echinococcosis under benzimidazole therapy using computed tomography. Chin Med J 2020;133:1507–1509.

doi.org/10.1097/CM9.0000000000000874

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