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Letters |
IRCCS S.Matteo, Pavia University Pavia 27100, Italy
We read with great interest the article by Karaoglanoglu et al. [1] that addressed experimentally the efficacy of scolicidal agents used in percutaneous treatments of echinococcal cysts of the liver. We think some remarks are needed. A minor one is that the authors used 3% sodium chloride solution, although it is widely known that 15–20% solutions are used for the puncture, aspiration, injection, reaspiration (PAIR) technique.
A more substantial point is that percutaneous treatments can be categorized in two groups: the first, those that aim at inactivation of the inner stratum of the endocyst, the germinal layer (e.g., the PAIR technique, radiofrequency thermal ablation); and the second, those that aim at evacuating the whole endocyst (e.g., percutaneous evacuation and other techniques using large-bore catheters). Thus, the claim by Karaoglanoglu et al. [1] that "unlike surgery, percutaneous drainage cannot extract the hydatid cyst membrane" is at odds with percutaneous evacuation being among their references. Quite logically, treatments in the second group generally make no use of scolicidal agents.
Inactivation or ablation of the germinal layer is key to treatment because this layer is where there is potential for regrowth—specifically, in the hundred brood capsules covering each square centimeter of the inner endocyst. Each brood capsule contains 4–5 protoscoleces, and each protoscolex can generate a daughter cyst. One can easily see why it is so difficult to "cure" an echinococcal cyst with any treatment other than radical surgery.
Treatments evacuating the whole cyst have been proposed as alternatives for types of cysts in which the PAIR technique is no longer indicated because it is associated with a high recurrence rate (i.e., multivesiculated and mostly solid with daughter cysts) [2]. Karaoglanoglu et al. [1] do in fact supply a theoretic background for such failures: If the scolicidal agent cannot penetrate the laminated layer of the daughter cysts that are not reached by the needle, there is no way the agent can reach the inner germinal layer. For this reason, the PAIR technique is currently indicated only for the treatment of unilocular echinococcal cysts and unilocular echinococcal cysts with a detached endocyst.
The procedures used in the treatment of group B, however, are rather cumbersome and catheter time may be long with an equally long hospital time [3]; these disadvantages may weaken their challenge to surgery. It is important that further experimental work be conducted in animals to investigate the effect of sodium hypochlorite not only on the host tissue (which we take here to be the pericyst) but most importantly on the biliary epithelium. Contact of any scolicidal agent with the biliary tree, due to biliary fistulas in the pericyst, is known to cause chemical cholangitis [4], a dreaded complication of the PAIR technique. If sodium hypochlorite is proven an exception to this rule, its use to dissolve the entire endocyst, including the germinal layer, could render obsolete the cumbersome techniques used to evacuate the whole cyst and allow patients with multivesiculated and mostly solid types of cysts to undergo the simpler, less expensive PAIR technique.
References
Harran University Medical Faculty Sanliurfa 63100, Turkey
We thank Brunetti et al. for their comments about our article [1] and would like to clarify some of their remarks. The importance of the main idea in our article—homogenize the cyst content and convert it to easily drainable form—has been emphasized in the manuscript as well. In fact, we tried to determine whether the cyst content could be melted with some pharmacologic or chemical agents.
Brunetti et al. criticized the percutaneous treatment classification and recommended another one. We think that the percutaneous evacuation classification recommended is a subgroup of the catheterization method and should be considered as such because there is an additional procedure performed after the catheterization of the cystic cavity. Also, Schipper et al. [2] described the technique as a "modified PAIR [puncture, aspiration, injection, reaspiration] method" in their article [2]. We believe that the catheterization method is more commonly used [3, 4] and more comprehensive statement comprising other methods as well.
We also think that the mentioned method is a reasonable treatment technique. However, it poses some notable problems. With small-diameter catheters, adequate evacuation, aspiration, and drainage cannot be achieved. As the diameter of the catheter increases, the incidence of complications elevated as well. In fact, the hospitalization period and the duration of catheterization are long, and it is not easy to convince patients to undergo such a procedure. Furthermore, this method is not new. Saremi at al. [5] developed a cutting device in 1992 to mechanically homogenize the cyst content and tried to aspirate the cyst membranes completely. Actually, one of the aims of our study was to minimize the unwanted consequences of such techniques.
It is inevitable that every chemical agent may have some potential risks. Also, some scolicidal agents are known to cause cholangitis. However, this association is not certain because it can be proven only through further studies. We believe that sodium hypochlorite might have such potential effects, so additional studies are needed to clarify as stated in the article.
In addition, most of the hydatid cysts are isolated formations from the host tissue and have a strong pericyst, and it is not necessary that all agents in the cystic cavity be in contact with the biliary system. The relationship of a hydatid cyst with the biliary tree depends on factors such as intracystic pressure and cyst diameter, some of which can be determined. However, the use of scolicidal agents in surgery and percutaneous treatment is generally accepted, and we believe that the opposite condition is not ethical because of some potential risks involved.
Brunetti at al. asked why we did not use the widely used 15–20% but 3% hypertonic saline. The critics may be right in that matter. However, our purpose was not to consider the scolicidal characteristics of the agents but to investigate their effects on the cyst membrane, a completely different characteristic of the agents. Therefore, we did not think it necessary to pick the agents that are used for clinical purposes and as scolicidal agents. Instead, we preferred 3% solution, which can be easily obtained. In another study (unpublished data), we used a higher concentration of hypertonic saline and observed that the increased concentration of the agent increased the disintegration of the membrane.
Although we believe that the results of our study [1] are important, this study is the first step of a planned series of studies and it is an in vitro study. We do not claim that the results may be used in the clinics directly, which may be possible after additional studies.
References
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