European Journal of Cardiovascular Medicine

The infection of the meta cestode stage of Echinococcus tapeworms is the cause of echinococcal illness. Ingested eggs from soil or water tainted by canine feces can infect humans, who are incidental hosts. Its embryos travel through the intestinal mucosa and enter the liver via portal vein, where the majority of the larvae encyst. Sometimes larvae can make it to the lungs and occasionally they can even make it past the liver and lung capillary filters and into the bloodstream. From bloodstream it can infect any organs. Although hydatid cysts can form in any organ in the body, they most commonly affect liver (50–80%) and lungs (15–47%).  [1]

Case series of four hydatid cyst cases:

1. Case 1 is a 5-year-old girl with a history of headache, loss of consciousness and seizure for the past 2 years. She was referred to the department of radiology to undergo an MRI scan. On MRI Brain, there is a large well-circumscribed T1 hypointense and T2 hyperintense cystic lesion with internal floating membrane (representing the detached laminatedendocyst ) on T2 / FLAIR and no obvious diffusion restriction,It is seen in the right temporo-parieto-occipital region (middle cerebral artery vascular territory ) which is causing  mass effect in the form of compression of the ipsilateral lateral ventricle complicating with bilateral hydrocephalus.  Lesion shows no surrounding edema, calcification, and no obvious contrast enhancement.

Multiple cystic lesions of variable sizes are also noticed in bilateral lobes of the liver on Ultrasound. All these findings are suggestive of disseminated cerebral hydatid cysts. (CE GRADE 3A).

Case 2 is a 12-year boy who has a history of cough, chest pain, and dyspnea. He was referred to the department of radiology for a Chest Xray.

On chest X-ray, a well-defined rounded radiopaque lesion is visible in the right middle zone. Underlying bones are normal.  Cardiac silhouette is maintained, trachea is central. Following it patient underwent CT for further evaluation. On HRCT, the right middle lobe has a well-defined thick-walled cystic lesion with focal costal pleura thickening and normal surrounding lung, suggestive of lung hydatid (CL). On axial T2 MRI, round hyperintense cystic lesion in the right middle lobe is noted.

Case 3 is a 15-year boy who presented with a history of pain abdomen.  He was a previously diagnosed case of liver hydatid cyst and has undergone PAIR on one of the largest cysts. He was referred to the department of Radiology for a routine follow up ultrasound.  On ultrasound there are multiple complex cystic lesions in liver parenchyma, with one of the cysts at segment VIII appearing to be ruptured and extending to the thorax. Some of the cysts show internal floating membrane. Few complex cysts are also seen in peritoneal Spaces (peri splenic, pelvis and left para colic gutter) suggestive of disseminated hydatid. On CT scan there is evidence of multiple variables sized well defined, mildly thick walled, rounded fluid attenuation hypodense lesions in both the lobes of liver, largest one in the right lobe (showing multilocation suggestive of daughter cysts). Multiple lesions are causing mass effect over biliary channels at porta causing mild intrahepatic biliary dilatation. Few of the cysts also show detached laminated membrane. There is evidence of air foci seen in one of the cysts which was treated with PAIR therapy previously.  There is also evidence of diffuse, variable sized, predominantly large similar kind of lesions in peritoneal Spaces (peri splenic, pelvis and left para colic gutter).  All the above findings are suggestive of liver hydatid disseminated into peritoneal spaces (grade CE3).

Case 4 is a 12-year female with history of pain abdomen, was referred to the department of radiology for an ultrasound scan. On imaging a well-defined cystic lesion with internal floating membrane giving water lily sign is seen in the segment VII of liver along with a focus of fat seen in the nondependent part of the cyst. Another small cyst is noted in the segment III of the left lobe of liver.

Axial CT shows rounded thin-walled cystic lesion in segment VII of liver with detached irregular laminated membrane corresponding to the detached daughter cyst. Two hypodense foci are seen in the nondependent part of the cyst likely fat. There is no evidence of perilesional edema, internal /peripheral calcification. (Grade CE3A hydatid)

Another cystic lesion with hyper dense periphery and discrete density internal content is seen in segment III of liver. (CE4 Hydatid).

Axial T2 MRI beautifully demonstrates WATER LILY SIGN (camalote sign) which occurs due to the detached endocyst.

Figure 1. (a) axial brain MRI scans shows a  well-defined T1  hypointense and T2 hyperintense cyst lesion seen in right temporo-parieto-occipital region  causing mass effect in form of compression of ipsilateral lateral ventricle and bilateral ventriculomegaly

(b)  T2 FLAIR axial MRI shows floating internal membrane along with low level internal content is seen. DWI and ADC showing no obvious restriction.

(c)  Ultrasound of liver shows multiple cyst in the liver parenchyma (d) Post operation specimen of brain hydatidcyst

Figure 2 (a) Plain Xray chest PA VIEW shows a well definedrounded radiopaque lesion in right middle zone.

(b) Axial CT shows a Thick walled outer isodense and inner hypodense cystic lesion in the right middle lobe with normal underlying lungs.

(c) Axial T2 MRI shows round hyperintense cystic lesion in the right middle lobe.

Figure 3 (a) Ultrasound of liver shows multiple complex cyst with internal floating membrane in both lobes of liver and one of the cyst at segment VIII of liver appears to ruptured and having subcapsular extension into the thorax .

(B) saggital and coronal  CT shows multiple cysts seen in the liver parenchyma and peri splenic region with internal septations and floating membrane and one of liver cysts having subcapsular component reaching up to thorax.  There is also evidence of diffuse variable sized large similar kind of lesion in  peritoneal Spaces (peri splenic, pelvis and left para colic gutter) shown with arrows.

(C ) Axial CT shows evidence of air foci seen in few of cyst which has undergone PAIR therapy previously  

Figure 4 (a) Ultrasound shows well defined thin wall cystic lesion in segment VII of liver with detached irregular laminated membrane within it , the lesion is also showing hyperechoic content within, which may be fat content. Another well-defined peripheral hypoechoic and internal hyperechoic content seen in segment III of left lobe of liver.

(b) Axial CT shows rounded thin-walled cystic lesion in segment VII of the liver with detached irregular laminated membrane corresponding to the detached daughter cyst, in non-dependent part of the cyst two hypo dense foci are seen likely fat, no evidence of peri lesion edema, internal /peripheral calcification seen. Another cystic lesion with hyper dense periphery and discrete density internal content is seen in segment III of liver.

(c) Axial T2 MRI beautifully demonstrates WATER LILY SIGN (camalote sign).

2001 WHO classification of hydatid cysts

Fig 5

Illustration of the layers of a liver hydatid cyst, comprising the outside (laminated) acellular layer, the inner (germinal) nucleated layer, and the granulomatous layer (adventitial layer), which is created by the host immune system to fend off the cystic infection. This image shows the daughter cyst floating inside the primary cyst, and the protoscolex—the future head of the adult worm—budding from the germinal layer. A sonographic result that combines protoscolices and cystic fluid is called hydatid sand.

The inner endocyst detaching from the outer pericyst exhibiting Water Lily sign (camalote sign).

A parasite illness known as hydatid disease primarily affects the liver, then the lung, though it can mimic many other diseases and affect nearly any organ in the body. The liver is the organ most typically affected (50–80%), with the most often involved region being the right lobe. The lesion appears multilocular due to daughter cysts that show vitality. The layers of a hydatid cyst, comprising the outside (laminated) acellular layer, the inner (germinal) nucleated layer, and the granulomatous layer (adventitial layer), which is created by the host immune system to fend off the cystic infection. [2]

The liver is the organ most typically afflicted (50–80%), with the most often involved region being the right lobe. Its symtoms depends on stage of presentation and its mass effect. The lesion appears multilocular due to daughter cysts that show vitality. Complete calcification of the cyst may happen as the illness progresses naturally. It is possible for complications to arise, including transdiaphragmatic migration into the thoracic cavity and rupture into the biliary tree. It’s a great mimicker and in the differential diagnosis, hemangioendotheliomas, biliary cysts, mesenchymalhamartomas, teratomas, simple liver cysts, choledochal cysts, Caroli's disease, and other cystic and

even solid liver lesions should all be taken into account. [3]

In youngsters, the most frequent location of involvement is

the lung (right lung more common 60%). Long-term asymptomatic progression of pulmonary hydatid cysts is possible, and pleural rupture can result in potentially fatal emergencies such as tension pneumothorax. It might be challenging to distinguish intact lung hydatid cysts from other lung cysts. Crescent-shaped lung hydatid cysts can resemble blood clots, mycetomas, Rasmussen aneurysms, and lung cancers.

In roughly 3% of cases of hydatid infestation, cerebral hydatid develops. Children account for 80% of cases of brain hydatids, which is caused by dysfunctional valves or patent ductusarteriosus and usually affects the middle cerebral artery (MCA) region. Brain hydatids can develop 1–10 cm annually. The size and location of brain hydatid cysts determine how they manifest clinically. As a differential diagnosis for cystic lesions such arachnoid cysts, porencephalic cysts, pyogenic abscesses, neurocysticercosis, and brain malignancies, brain hydatid cysts should be considered.

The most common cause of peritoneal hydatid cysts is the rupture of hepatic hydatid cysts into the peritoneal cavity. Intestinal duplication cysts and mesenteric cysts are among the differential diagnosis. Hydatid cysts can impact a wide range of organs, including the seminal vesicles, uterus and adnexa, pancreas, thyroid gland, gallbladder, skin, bones, muscles and subcutaneous tissue.

In this case series, we detailed cases of lung, cerebral, and disseminated liver hydatid in children. A thorough understanding of the imaging results and differential diagnosis of hydatid cysts will facilitate prompt diagnosis and help in direct treatment decisions. Imaging can also reveal the extension and complications of hydatid cysts.

1. MaskalRevannaSrinivas et al. Imaging Spectrum of Hydatid Disease: Usual and Unusual Locations
2. Sultan AbdulwadoudAlshoabi et al. Hydatid Disease: A Radiological Pictorial Review of a Great Neoplasms Mimicker
3. Olat P, Kantarci M, Alper F et al. Hydatid disease from head to toe. Radiographics. 2003; 23:475–94.