Case No. :	28
Month :	April
Year :	2001
Contributor :	Dr. Prashant Patil

Case Report | Discussion

Case report:

Clinical profile:

A 28 year old lady presented with complaints of dry cough and mild fever on and off since 4 years. She also complained of anorexia and subjective weight loss with Grade 2 dyspnea since 2-3 years. Her blood counts were normal.

Frontal and lateral chest radiographs were obtained, which revealed the presence of multiple well defined rounded soft tissue opacities ranging in size from 7 cm to 10 cm in diameter, these opacities were seen in both lung fields.

Fig 1	Fig 2.

These show a well defined, 4x4 cm, homogenous soft tissue density shadow in right mid and lower zones. No calcification or cavitation is seen within the lesion. Another oval 3x2 cm in size homogenous soft tissue density in right mid zone is also seen. A large, thin walled radiolucent shadow measuring 4x4 cm in size is seen in left paracardiac region in left mid zone. Inhomogenous and illdefined soft tissue densities are seen within it . In addition, a large illdefined homogenous soft tissue shadow seen in left mid zone in its lateral half. Haziness is seen in left basal region.

In view of multiple soft tissue density lesions along with a "cavitary" lesion in the left paracardiac region, the first radiographic impression was of hydatid cysts with rupture of the left paracardiac cyst with consolidation in left basal region. However the possibility of secondaries in lung had to be considered.

CT scans of the chest were then obtained.

Fig 3	Fig 4.

 

The post contrast film shows multiple, peripherally enhancing, hypodense homogenous areas of fluid attenuation in both lungs parenchyma. The adjacent lung parenchyma shows atelectatic changes on lung windows.

These findings were considered to be diagnostic of multiple parenchymal hydatid cysts.

Ultrasonography of the abdomen and pelvis was normal. The bronchial lavage did not show any malignant cells seen.

Serum CEA,AFP and Beta HCG: within normal range. Immunoglobulins study: IgG for ecchinococcus was positive >1:300. normal range is >1:20.

 

Discussion:

The differential diagnosis of such lesion are- 1. Multiple hydatid cysts. 2. Multiple lung abscesses, 3. Loculated pleural effusion, 4.Metastasis .

Hydatid disease of the lung presents as single or multiple, well defined, soft tissue density masses. There is generally no air density seen within this mass unless there is communication with the bronchial tree. Calcification within the hydatid cyst is very rare in the lung. Multiple lung abscesses are generally small, well defined, soft tissue density masses in an immunocompromised patient which may show air shadows within it. There may be associated consolidation. Loculated pleural effusions are peripheral shadows, which are pleural based, varying in size and on lateral radiographs. the antero posterior diameter is wider than the transverse diameter on frontal view. Multiple cannon ball shadows, mainly in the mid and lower zones with or without calcification goe in favor of metastasis.

Hydatid disease is caused by the tapeworm Ecchinococcus granulosus and Ecchinococcus multilocularis. Dogs are the usual primary host and the intermediate host is usually sheep or a cow, sometimes human. The disease is endemic in sheep raising areas of Australia, South America, North Africa and Greece.

Life cycle:-The adult worm lives in the small intestine of the primary host. Ova are passed in the feces and ingested by intermediate host. Larvae develop in the duodenum of the new host, where they enter the blood stream and travel to the liver and lungs and occasionally even the systemic circulation. Pleural or pulmonary involvement may also occur due to direct extension through the diaphragm from hydatid disease in liver. The life cycle is completed when another primary host eats the remains of an infected intermediate host.

As the hydatid cyst grows, it compresses the adjacent lung into a fibrotic capsule known as pericyst. The cyst itself has a thin smooth wall composed of two adherent layers, the laminated ectocyst and the delicate inner lining - the endocyst from which hang the daughter cysts. The pulmonary cyst grows rapidly and approximately 2/3rd rupture. Most rupture into the surrounding lung and bronchial tree, causing secondary infection. Rupture may result in an acute allergic reaction.

The cardinal radiographic features are one or more spherical or oval, well-defined, smooth masses of homogenous density usually in the middle or lower zones. Multiple cysts are seen in 1/3rd of patients and are bilateral in 20% of patients. There is a predilection for the lower lobes, the posterior segments and the right lung. CT scanning reveals fluid content within the cyst with a density close to that of water. Daughter cysts, when present, appear as curved septations. At CT, the wall thickness ranges from 2mm to 1cm. The rate of growth may be fairly be rapid, with doubling times of less than 6 months. A striking feature is that the cyst is really pliant and molds to adjacent structures, resulting in indentation, lobulation or flattening. Calcification is rare in lung hydatid, as compared to liver hydatid.

If the pericyst ruptures, air dissecting between the fibrotic lung forming the pericyst and the ectocyst of the parasite leads to a visible crescent of air between the two and is known as the meniscus sign or crescent sign. If the cyst itself ruptures, an air-fluid level results and daughter cysts may be seen floating in residual fluid. Sometimes, the cyst wall is seen crumpled up and floating in fluid which lies within the non-collapsed pericyst. This pathognomic appearance is described as water-lilly sign.. All these signs are well demonstrated on CT and MRI.