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Treatment of Cystic Hydatid Disease

The role of surgery in the treatment of hydatid disease is diminishing, with increased indications for, and success with, chemotherapy and with the introduction of PAIR (Puncture-Aspiration-Injection-Reaspiration). The ability to treat hydatidosis with chemotherapy is an immense step forward in the management of this widespread disease. Guidelines for treatment in humans were published in 1996 by the World Health Organization (WHO). At that time surgery was recommended as the first choice for treatment wherever possible to totally remove the parasite (Fig.3.153). However, chemotherapy with benzimidazole compounds (albendazole or mebendazole) or other suitable drugs, combined with diagnostic aspiration and the injection and reaspiration of sterilizing fluid when cysts cannot be removed, is a valid alternative therapy.

Fig. 3.153 Surgical removal of endocyst from the opened pericyst of a lung hydatid. The white endocyst is fragile and easily torn. When the surgeon opens the endocyst and hydatid fluid escapes, the endocyst falls away from the pericyst (arrow), as it does when a cyst ruptures. The surgeon must search for and oversew perforating bile ducts during endocystectomy of liver hydatids to prevent development of cysto-biliary fistulas, but perforating bronchi in lung hydatids are usually not ligated. (Courtesy of Dr. Lewall).

Patients are usually pretreated for a short time (10 to 14 days) with an antiscolicidal agent such as albendazole prior to definitive surgery or percutaneous drainage, and for several weeks after the procedure (see Fig. 3.81). An excessive period of pretreatment is dangerous as it may precipitate communicating or direct rupture (Fig. 3.29) Although various surgical methods have their advocates, centers with wide experience tend to favor the most conservative approach -endocystectomy. Many authors recommend that Type II cysts should not be drained percutaneously because of the difficulty removing daughter cysts and matrix, although there are dissenting opinions, especially if only daughters are present as they can be punctured individually. Time and experience will tell whether uncomplicated hypermature Type II cysts actually require resection. Hypermaturity is probably a terminal stage prior to death and conversion to a clinically insignificant Type III lesion. Moreover, intuition suggests that hypermature lesions must be physically stable and resistant to rupture, especially if they are surrounded by substantial pericyst and organ parenchyma (the thickness of pericyst is difficult to estimate by CT or US but MRI may be helpful).

Expansile lesions have sometimes been resected, even if the diagnosis of hydatid disease was not confirmed. However, in patients with multiple bilateral or multiorgan cysts, or when cysts have ruptured, disseminated or recurred, surgery cannot cure the patient. In such cases, the diagnosis of hydatid disease must be confirmed (WHO Informal Working Group on Echinococcosis, 1996) because chemotherapy is not always without complications and has to be continued for several months or even years.

When clinical findings, serology and medical imaging are inconclusive, fine needle biopsy under the protection of antihelminthic prophylaxis should be considered to confirm the diagnosis. Ultrasound- or CT-guided diagnostic cyst puncture (Figs. 3.150, 3.151) should only be performed after other diagnostic methods have failed. The PAIR procedure consists of percutaneous puncture of cysts, aspiration of substantial amounts of cyst fluid, injection of protoscolicidal substances (such as 20% sodium chloride solution, cetrimide, or 95% ethanol) for a minimum of 15 minutes, and then re-aspiration of the fluid cyst content. When properly performed by trained radiologists and physicians, PAIR has proven safe and effective; more than 500 favorable PAIR interventions have been reported with a 5 year follow-up period. The combination of risk, benefits, indications and contraindications for surgery, chemotherapy, and the PAIR procedure have been modified from WHO (1996) recommendations. Those of particular interest to radiologists can be summarized as follows:

The surgical complication rate postoperatively is 10-25%. The operative mortality is probably less than 2%. The long term recurrence rate after surgery is 2-10%. Seroconversion (from positive to negative) after surgery usually occurs within one year but may take up to four years. When the infection recurs, the serology becomes positive again.

Drainage of Type I cysts is gaining acceptance but it should be avoided if pericystic ducts are dilated (Figs. 3.22 and 3.154A ) because the inevitable communicating rupture may precipitate biliary obstruction. Even in the absence of visibly dilated ducts, aspirated fluid should be checked for bile and, as an additional precaution, a cystogram may be performed to ensure that the cyst does not communicate with the biliary tree. Communication is demonstrated more often at surgery than by noninvasive imaging, indicating that it is underdiagnosed preoperatively. Sclerosing solutions such as formalin or silver nitrate should never be injected into a liver cyst for fear of causing sclerosing cholangitis. Moreover, perforating bile ducts carry hypertonic saline to the gut from where it is absorbed, causing hypernatremia and sometimes congestive heart failure. For this reason cetrimide has become the favored scolicidal agent in most, but not all, centers. Percutaneous drainage is not advisable if the cyst cannot be approached through normal parenchyma of the host organ or when the pericyst is insubstantial, because of the danger of direct rupture, dissemination, and anaphylaxis.


Fig. 3.154 Therapy of liver hydatid cysts. (A) Noncontrast CT scan showing palliative surgery done by the radiologist as a simple tube drainage of infected or communicating cysts. (B and C) Chemotherapy with mebendazole in another Saudi patient who had surgical removal of hepatic cysts 8 years earlier. Follow-up contrast-enhanced CT scan revealed recurrence of hydatids in both liver lobes (B). Mebendazole produced radiologically apparent regression after several months treatment (C). (Courtesy of Dr. von Sinner and Semin in Roentgenol, 1997).

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