Teaching Case

A 66-year-old man consulted the emergency department for dyspnea, dry cough and weight loss.

At arrival, his blood oxygen saturation was 85%. And biochemical analytics showed increased bilirubin and acute phase reactants.

Chest X ray with bilateral low density homogeneous pulmonary masses and right diaphragmatic elevation (Figure 1).

In order to complete the study, an enhanced CT was performed.

Sagittal and coronal image reconstruction in the mediastinal and lung windows present bilateral and multiples cysts with well-defined borders (asterisk). On the right upper lobe one of the cysts shows air crescent and air bubble sign (arrowheads).  Compression of the right diaphragm by hepatic hydatic cysts can also be seen. (Figure 2).

Thoracic axial and coronal MIP reconstruction revealed cystic nodules (arrowhead) that caused luminal widening in apical segmental artery of the right upper lobe, anterior and apical segmental arteries of the left upper lobe consistent with emboli. (Figure 3) Ground glass area in the left upper lobe probably related to incipient infarction (arrow). (Figure 2b)

On abdominal CT in the portal venous phase multiples liver cysts with peritoneal dissemination can be seen (asterisk). The one on the right hepatic lobe (arrow) presents daughter vesicles inside (type II) and biliary dilatation (arrowhead) as an indirect sign of intrabiliary rupture of hepatic hydatic cyst (Figure 4).

Musculoskeletal involvement was also manifested with a low-density lesion next to left scapula with bone erosion. (Figure 5).

Background

Hydatidosis is a parasitic disease caused by the larvae of the tapeworm Echinococcus. There are two main forms of the disease in humans: cystic echinococcosis caused by E. granulosis which is the most common and alveolar echinococcosis due to E. multilocularis. [1]

Echinococcus granulosis, has carnivores (e.g. dogs, cats…) as definitive hosts. E. granulosis can be transmitted to humans by ingestion of food or water contaminated by the faeces of parasitized carnivores.

Clinical and Imaging Perspective

Liver and lungs are the organs most commonly affected and show characteristic imaging findings. Bones, kidneys, spleen, muscles and central nervous system involvement may be seen due to hematogenous dissemination. [3,8,9]

Radiography is the initial imaging modality but multimodality imaging approach can be used including US, MRI or CT [9]. CT allows to classified cysts depending on the stage of the disease ( useful for the detection of intralesional calcifications) and to identify complications. [4, 8]

Cysts could be asymptomatic for many years, and become painful when they reach a larger volume. Most of their complications are related to their rupture to adjacent structures such as the biliary tree, the pleura or the peritoneum that may be silent clinically or cause anaphylaxis. [2,4]

Uncomplicated hydatid cysts of the lung are usually asymptomatic, while complicated cysts present with nonspecific clinical features like coughing, chest pain, an hemoptysis. [3]

Ruptures may be classified in:

• contained (detachment of the pericyst from the endocyst)
• communicating (with the bronchus)
• direct (rupture of all membranes with spillage of contents) [3]

Some imaging signs of contained rupture hydatic cyst are:

• air crescent sign ( a thin crescent of air seen between the pericyst and endocyst caused by bronchial erosion)
• air bubble sign (small intracyst air blebs are seen at the periphery of the cyst between the pericyst and endocyst). [3-8]

Hepatic hydatic cysts may also present complications like infection or rupture. Rupture occurs in 35% of the cases and the most common type is the communicating rupture(15%). Communicating rupture within the biliary tree can be detected by indirect signs such as the presence of fat, air or airfluids levels within the cysts, deformation of the cysts, focal defect on the cystic wall or biliary tree dilatation [5,6].

Pulmonary or systemic embolism caused by hydatic cysts are rare complications. Hepatic echinocci may open to the inferior vena cava and daughter vesicles may cause embolisms in the pulmonary arteries. [7]
Muskuloskeltal involvement is also very rare and may cause bone erosion.[10]

Outcome

Medical treatment with albendazol and surgical intervention (Lagrot cyst perichystectomy) were performed in this case.