Explore UAB

Gorgas Case 2015-04

Epidemiology: Born and lives in Lima. Works as a university teacher. Owned dogs until 10 years ago, but no exposures on farms or to farm animals. Heavy smoker (1.5 packs per day for the past 30 years). He denies TB, TB contact, or exposure to ill persons.

Physical Examination: Afebrile. Heart rate 100, respiratory rate 30, BP 120/60, temperature 37°C, SatO2 95%. Acutely ill with severe respiratory distress. No edema, no cyanosis, no lymphadenopathy. Lungs: breath sounds absent, diffuse crackles in the left lung. Heart: heart sounds regular, tachycardic, no murmurs or gallops, no jugular venous distension. Abdomen: non-tender, non-distended, no hepatomegaly or splenomegaly. Remainder of the exam was unremarkable.

Discussion: In limited resource environments, ultrasound is a highly effective diagnostic modality for many diseases, including hydatid disease (echinococcosis) of the liver and lung. In this case the ultrasound is diagnostic showing a single massive fluid-filled cyst with many thin-walled fluid-filled daughter cysts appearing as symmetrical round septated lesions within the parent cyst. The image shows a solid area plus daughter vesicles making this a stage CE3b in the WHO ultrasound classification. This video image was obtained using a sector probe (cardiac transducer), as the cysts were quite deep in the lung. A linear probe, which is frequently used for scanning the lung, will not image deep enough to view these cysts and they will consequently be missed since they are not against the pleural surface. In this case a CT scan of the lung [Image B] was also obtained, which did not add any diagnostic advantage but did help guide the eventual surgical approach. CT scan of the liver [Image C] disclosed multiple calcified lesions compatible with inactive dead hepatic hydatid cysts. The imaging here is diagnostic without any further serology (usually a Western blot) or diagnostic procedure. Serology is usually positive with solitary hepatic cysts but sensitivity drops below 50% with solitary pulmonary cysts even when the cyst is large such as this.

Ultrasound is the standard of care for imaging echinococcosis of the liver and abdominal organs in resource limited settings; not only can ultrasound be diagnostic but it can also direct treatment. However, ultrasound for the diagnosis of pulmonary echinococcosis has not been widely utilized. There are several reasons why pulmonary ultrasound for the diagnosis of echinococcosis lags behind hepatic ultrasound for echinococcosis: (1) lung cysts tend to be less frequent than liver cysts, (2) sonographers and sonologists are less experienced with lung ultrasound compared to hepatic ultrasound, and (3) detection of pulmonary echinococcosis is dependent on the size and location of the cyst. Cysts that lie against the pleura or pericardial surface are fairly easy to image, whereas, cysts that lie deep within the lung are difficult or not possible to visualize thus limiting the utility of ultrasound for echinococcosis of the lung. Ultrasound of the lung can effectively rule in echinococcosis, but for the above reason, it cannot rule out echinococcosis due to the difficulty of obtaining images of cysts deep within the lung. The characteristic double wall that is seen in hepatic echinococcosis is also seen and diagnostic in pulmonary echinococcosis.

Treatment of pulmonary hydatid is surgical and most surgeons will not operate if pre-operative albendazole has been given as this softens the cyst wall somewhat. The patient underwent a right thoracostomy with decortication and cystectomy. Image D shows a giant hydatid cyst (volume 4,000 ml). Noted were viable daughter cysts, some with 2 complicated cysts containing purulent hydatid fluid raising suspicion of a transdiaphragmatic liver fistula. Previous pulmonary hydatid cases we have shown are Gorgas Cases 2013-01 and 2011-05. In adults the expectoration of salty-tasting fluid with or without pieces of white membranous material is highly characteristic of a fistula or frank rupture of a cyst into a bronchus, but this patient did not describe this.

Human hydatid disease secondary to Echinococcus granulosus is caused by the larval form of this dog tapeworm. Humans ingest the tapeworm eggs in environments contaminated by canine feces and become accidental intermediate hosts. Sheep are the normal intermediate hosts. In general, disease is diagnosed in adulthood as larval cysts expand slowly over years or decades, becoming symptomatic as they impinge on other structures by virtue of their size. The cysts contain hundreds of viable protoscoleces capable of becoming adult tapeworms upon ingestion by a definitive host such as the dog. The internal germinal membrane lining the cyst produces new protoscoleces on an ongoing basis. Each protoscolex is capable of becoming a new daughter cyst should the original cyst rupture or be ruptured.

Cystic hydatid disease due to E. granulosus is common in sheep and cattle raising areas worldwide. Most primary infections involve a single cyst. In adults, 65% of solitary cysts are found in liver, 25% in lung and the rest in a wide variety of other organs including kidney, spleen, heart, bone and brain. In patients with a pulmonary cyst, approximately 18% will also have a hepatic cyst. The patient has not pursued abdominal imaging at this point.

Surgery may involve excision of the cyst or resection of the cyst and the immediate surrounding parenchyma. Despite the lack of consensus, the currently most accepted surgical treatment for lung hydatid is complete excision using parenchyma-preserving methods, such as cystostomy, intact cyst enucleation or removal after needle aspiration preserving as much lung parenchyma as possible. Resection techniques such as pneumonectomy and segmentectomy should be reserved to cysts involving whole hemithorax or the whole segment respectively; and lobectomy generally should be performed only in large abscessed cysts. Most surgeons use pads soaked in hypertonic saline to protect the operatory field from spillage and subsequent seeding of new cysts.

Albendazole is the therapy of choice for intact cysts that are not operable, such as when there are multiple or disseminated cysts. A trial of continuous albendazole may also be considered for solitary cysts that are less than about 5 cm. Response is generally slow. Albendazole should be immediately instituted in ruptures whether they be spontaneous, post-traumatic or the result of a surgical accident. Praziquantel is the most potent scolicidal drug and is the drug of choice for all adult tapeworms. Praziquantel gets into the cysts and is slowly cidal to the protoscolices. In hydatid disease, animal studies show improved scolicidal activity of the combination of albendazole and praziquantel compared to albendazole alone. Praziquantel is ineffective against the germinal membrane of cysts. Thus, praziquantel is especially useful as an acute therapy when a cyst ruptures (spontaneously, or intra-operatively due to surgical mishap) and scoleces are lying free before encysting again. Combination therapy is used in some experienced centers pre-operatively.