Paragonimiasis diagnosed by CT-guided transthoracic lung biopsy: Literature review and case report

Abstract

More than 40 different species of the parasitic flatworm Paragonimus have been identified worldwide, including in Vietnam, but only 10 species are known to cause disease in humans, particularly Paragonimus westermani. Paragonimus are transmitted through the ingestion of raw foods, especially freshwater shrimp, and crab. Paragonimiasis causes pneumonia, which can present as acute or chronic, with symptoms including prolonged cough, chest pain, shortness of breath, and hemoptysis. Hematologic changes include eosinophilia and the presence of specific antibodies for Paragonimus in the blood. Diagnosis is confirmed when Paragonimus specimens or eggs are found in the sputum or pleural fluid. The specificity of imaging is not high, but imaging can be used to guide the diagnosis. After the failure of microbiological diagnostic methods, lung biopsy can be used to confirm a diagnosis of paragonimiasis. We present a paragonimiasis case associated with unique features, including epidemiologic factors, atypical clinical signs, no increases in blood eosinophils, and negative microbiological tests. Although the patient was suspected of tuberculosis or lung cancer, imaging studies were consistent with the presence of lung flukes. Three transthoracic lung biopsies were performed, and pathology revealed a cystic structure containing Paragonimus on the third biopsy.

Keywords: Computed tomography; Lung fluke; Paragonimiasis; Paragonimus; Paragonimus westermani.

Fig. 1

Chest X-ray images from the first time of the patient to our hospital appears many diffuse opacities with different sizes, distributed throughout both lung.

Fig. 2

CT image of chest, lung window (A-C) and mediastinal window (D) Before contrast injection; (E-F) After contrast injection). (A-C) 3 lower slices of carina showing multiple nodules, 1-3 mm in size, round, smooth, few nodules involving pulmonary vessels (red arrow). (D) Before contrast injection, mediastinal window, many nodules, irregular size, heterogeneous density, with calcified components (yellow arrow). (E-F) Chest CT after contrast injection shows strongly contoured nodule, with no enhancement in the nodule (yellow arrow). The radiologist thinks highly of the possibility of malignancy spreading to the lungs (metastasis), but does not rule out the presence of inflammatory nodules due to parasites. (Color version of the figure is available online.)

Fig. 3

First transthoracic lung biopsy images. (A) In the prone position of the patient, determine the nodule will be biopsied (yellow arrow). (B) Image of a 20 G coaxial core biopsy needle inserted into the node (yellow arrow). Three pieces of node have been cut. (C) After the needle is removed, there is light bleeding in the cut area, no pneumothorax (red arrow). (Color version of the figure is available online.)

Fig. 4

Microscopic pathology results for the first lung biopsy specimens. Hematoxylin and eosin (HE) stain (× 40; Code 0282 – B18) revealed the biopsy fragments consisted of alveolar tissue, fibrous connective tissue, polymorphonuclear leukocytes, mononuclear inflammatory cells, and macrophages (red arrow), indicative of chronic inflammatory lesions. (Color version of the figure is available online.)

Fig. 5

Chest X-ray, PA of the patient at the second examination. Compared with the radiograph in Figure 1, we see that the density of opacities increases significantly. The patient had a second chest CT scan, detailed images are shown in Figure 6.

Fig. 6

CT images of the patient from the second examination at the NLH. The results were compared with previous images. (A) cross section representing the parenchymal window shows many nodules with similar morphology to the previous image but with higher density. The nodules have a well-defined border, but some fused nodules appear morphologically. B: Representative view of mediastinal window after intravenous contrast injection: Multiple nodules have similar contrast morphology to the first scan. The radiologist concluded that lung injury could be caused by parasitic diseases, but these results need to be differentiated to rule out pulmonary tuberculosis.

Fig. 7

Second transthoracic lung biopsy. (A) and (B) The patient was supine, and an 18 G core biopsy needle was used to pierce the lung wall from the front targeting a 3-mm nodule near the chest wall (white arrow), which obtained 3 pieces of the specimen. (C) After the biopsy needle was removed, no complications were observed at the injection site (red arrow). (Color version of the figure is available online.)

Fig. 8

Microscopic pathology of the second lung biopsy specimens. Hematoxylin and eosin (HE) stained slide (x20), Code 1791 - B18 shows the biopsy specimen, revealing the alveolar wall (blue arrow), fibrous connective tissue, infiltrating lymphocytes, and macrophages. The lung tissue appeared benign, with no evidence of tuberculosis or tumor lesions.

Fig. 9

Third transthoracic lung biopsy. (A) and (B) In the prone position of the patient, and an 18G coaxial needle was inserted from the back to target a 5-mm nodule deep in the parenchyma of the left lower lobe (red arrow) obtaining 3 specimens. (C) After the biopsy needle was removed, no complications were observed at the insertion site (yellow arrow). (Color version of the figure is available online.)

Fig. 10

Microscopic pathology of the lung third biopsy specimen. (A) Hematoxylin and eosin (HE)-stained slide (× 40) show clear alveolar structures that were within normal morphologic limits (red arrow). (B) In the stromal area, fibrous proliferation was observed, and a section of Paragonimus was observed in the vascular lumen (blue arrow); no malignant lesions were observed. The histopathological images were consistent with paragonimiasis (Color version of the figure is available online.)