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Multiple pulmonary nodules: diagnosis in an young afebrile patient

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Q1: What is the diagnosis?

Pulmonary hydatid disease.

Q2: What is the differential diagnosis?

Differential diagnosis of multiple pulmonary nodules includes neoplastic, infective, immunological, and vascular causes (see box 1).

Box 1: Differential diagnosis of multiple pulmonary nodules

  • Metastasis.

  • Abscess.

  • Hydatid cyst.

  • Fungal infection.

  • Wegener’s granulomatosis.

  • Rheumatoid nodule.

  • Septic embolus.

  • Arteriovenous malformation.

Q3: How does this condition present?

The majority of intact pulmonary cysts are known to produce no symptoms or are occasionally responsible for a non-productive cough or minimal haemoptysis.1 However, when the cyst ruptures, an abrupt onset of cough, haemoptysis, sputum, fever, chest pain, expectoration, and life threatening anaphylactic reaction may develop.2 The expectoration of membrane and/or hydatid sand is a clinically diagnostic indicator of ruptured hydatid cyst.

Other symptoms may arise such as Horner’s syndrome from superior sulcus cysts, bone pain from posterior mediastinal cysts, dyspnoea from tracheal compression, haemorrhage due to erosion of great vessels, and tension pneumothorax.1

Q4: What other tests should be performed?

These include serological tests, sputum examination, and abdominal sonography. Serological studies in hydatid disease includes complement fixation test, indirect haemagglutination test, and Casoni’s intradermal test. Positive serology is said to be lower in children and high in adults.1 Microscopic examination of the sputum may reveal hooklet from scolices.

Abdominal sonography is required to look for other possible sites of involvement—liver, spleen, pancreas, and kidneys.

Q5: What is the pathogenesis of the crescent sign?

The crescent or meniscus sign is produced when an enlarging cyst eventually erodes the bronchioles and with coughing and straining air may be introduced between the pericyst and endocyst, producing a radiolucent air shadow in the form of crescent meniscus.1

Q6: What are other causes of the crescent sign?

This sign is highly reliable, but not pathognomonic of hydatid cyst because a similar appearance may be produced by intracavitary fungus ball, blood clot, pulmonary gangrene, and air cap within a tumour.4

Final diagnosis

Pulmonary hydatid disease.


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