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Two cases of hydatid cysts in lung and exophytic lesion in the left lobe of liver diagnosed in last two days on CT.
Labels: echinococcus, hydatid, hydatid cyst
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Hydatid cysts of the liver exert pressure on the
surrounding parenchyma, and in approximately one-fourth of the cases,
due to higher pressure in the cyst, the cysts eventually leak into
small bile ducts or perforate into large ones. Thus the most common
complication of hydatid cyst of the liver is spontaneous rupture into
the biliary tract. Intrabiliary rupture occurs into the right duct in
55–60% of cases, into the left duct in 25–30% and rarely into the
confluence or gall bladder.
This
is a case of a hydatid cyst of the left lobe with MRCP images which
ruptured spontaneously into the left hepatic duct. Thick slab and Thin
Slab images are shown, with communication with hydatid cyst and left
hepatic duct and intraluminal linear filling defects.
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a) Unilocular Hydatid cyst:
Conventional Ultrasound utilizing the pathgnomonic WSC (El Fortia Criteria) is superior in identifying Hydatid cysts among other non-hydatic in nature [1-6]. The WSC (Fig. 4 a-c & 5 a-c & 6 a-b) which was simply applied by showing the pericystic reaction in the organ tissue and the ectocyt as a double layered wall. It is based on magnification of the cyst wall at the cyst / organ interface indicating double layers in case of the unilocular cysts and their internal septa in case of multilocular cysts.
If the adventitia was not or faintly seen we should search for a sonolucent rim at the site of interface between the organ tissue and cyst. This rim represents a slit of viscus fluid which is sonographiocally considered as an indirect sign for the existence of adventitia. In this patient seen in ( Fig 6a), the huge cyst was attached to a small area of the host' organ (about 2 cm attached area) which does not permit to the host organ to react against cyst strongly, therefore the adventitia was seen very faint.
But also in the case of ( Fig 6b), the adventitia can not be visualized although the cyst is embedded into the liver tissue, most probably was due to decreased immunity of the patient.
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Hydatid disease is one of the oldest diseases known to man. It was first described in the Talmud as a "Bladder full of water" [1-2]. Hippocrates described the human Echinococcus disease more than two thousand year ago with a very interesting expression (liver filled with water) [3]. Al-Rahzes, subsequently wrote detailed script on hydatid cyst of the liver about one thousand years ago [4]. However, the exact life cycle of the parasite was only recognized in 1928 by Dew et al. [1-2].
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Infection cycle
 Like many other parasite infections, the course of Echinococcus infection is complex. The worm has a life cycle that requires definitive hosts and intermediate hosts. Definitive hosts are normally carnivores such as dogs, while intermediate hosts are usually herbivores such as sheep and cattle. Humans also function as intermediate hosts, although they are usually a 'dead end' for the parasitic infection cycle.
The disease cycle begins with an adult tapeworm infecting the intestinal tract of the definitive host. The adult tapeworm then produces eggs which are expelled in the host's feces. Intermediate hosts become infected by ingesting the eggs of the parasite. Inside the intermediate host, the eggs hatch and release tiny hooked embryos which travel in the bloodstream, eventually lodging in an organ such as the liver, lungs and/or kidneys. There, they develop into hydatid cysts. Inside these cysts grow thousands of tapeworm larvae, the next stage in the life cycle of the parasite. When the intermediate host is predated or scavenged by the definitive host, the larvae are eaten and develop into adult tapeworms, and the infection cycle restarts.
Disease symptoms
As already noted, Echinococcus infection causes large cysts to develop in intermediate hosts. Disease symptoms arise as the cysts grow bigger and start eroding and/or putting pressure on blood vessels and organs. Large cysts can also cause shock if they happen to rupture.
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