B67.31 Echinococcus granulosus infection, thyroid gland

Name of the Condition

• Echinococcus granulosus infection, thyroid gland

Summary

Echinococcus granulosus infection of the thyroid gland is a parasitic condition caused by the tapeworm Echinococcus granulosus. It involves the formation of cysts in the thyroid gland, resulting from ingesting parasite eggs. This zoonotic infection may be asymptomatic or cause symptoms depending on cyst size, location, and complications. It is part of cystic echinococcosis, the most common form of echinococcosis.

Causes

The infection is caused by ingesting eggs of Echinococcus granulosus, which are shed in the feces of infected definitive hosts (typically dogs, foxes, or other canids). These eggs contaminate soil, water, or food. Upon ingestion, the eggs hatch in the human intestine, releasing larvae that migrate to the thyroid gland and develop into cysts. The cysts grow slowly over years, potentially causing tissue damage or complications.

Risk Factors

• Living in or traveling to regions where the parasite is endemic (e.g., parts of South America, Africa, Asia, or Eastern Europe).
• Close contact with dogs or other definitive hosts, especially in rural or pastoral settings.
• Ingesting food or water contaminated with parasite eggs.
• Occupational exposure, such as farming or animal husbandry.
• Lack of access to clean water or sanitation in endemic areas.

Symptoms

Symptoms may include a palpable neck mass, difficulty swallowing, hoarseness, or pressure symptoms if the cyst is large. Some individuals may remain asymptomatic, with the infection discovered incidentally during imaging for unrelated reasons.

Diagnosis

Diagnosis typically involves imaging studies (e.g., ultrasound, CT, or MRI) to identify cysts in the thyroid gland. Serological tests for Echinococcus antibodies may support the diagnosis. Fine-needle aspiration or biopsy may be performed to confirm the presence of cysts, though this is done cautiously to avoid rupture.

Treatment Options

Treatment may include antiparasitic medications (e.g., albendazole) to target the cysts, often combined with surgical removal of the cysts. Percutaneous drainage or ablation techniques may be used in select cases. The choice of treatment depends on cyst size, location, and patient health.

Prognosis and Follow-Up

Prognosis is generally good with appropriate treatment, though complications (e.g., cyst rupture or infection) can occur. Follow-up imaging and serological testing are recommended to monitor for recurrence or residual disease. Long-term management may be necessary to prevent relapse.

Complications

Potential complications include cyst rupture, which can lead to anaphylaxis or dissemination of the parasite, secondary bacterial infection of the cyst, or compression of nearby structures (e.g., trachea or esophagus) causing respiratory or swallowing difficulties.

Lifestyle & Prevention

Preventive measures include avoiding contact with feces of dogs or other canids, practicing good hygiene (e.g., handwashing), and ensuring food and water are free from contamination. In endemic areas, deworming pets and avoiding consumption of raw vegetables or water from untrusted sources may reduce risk.

When to Seek Professional Help

Seek medical attention if you experience a new or growing neck mass, difficulty swallowing, hoarseness, or signs of infection (e.g., fever, pain). Prompt evaluation is important to prevent complications and initiate treatment.

Tips for Medical Coders

Code B67.31 is specific to Echinococcus granulosus infection of the thyroid gland. Documentation should specify the site (thyroid gland) and confirm the causative organism (Echinococcus granulosus) to support accurate coding. Ensure the diagnosis aligns with clinical findings and imaging results.