Hydatid disease (cystic Echinococcus) caused by Echinococcus granulosus is an endemic disease and a significant public health problem in many parts of the world. The Mediterranean basin, Middle East, South America and some parts of Africa are among those hit hard by hydatid disease. Interventional radiology has several solutions to offer, writes Okan Akhan.
Hydatid disease is called a neglected disease of mankind, partly due to the fact that it is mainly a disease of rural areas and economically weak communities in developing countries. The clinical findings are vague and diagnosis is difficult. Although some serological tests are used for the diagnosis, they can be inaccurate.
The diagnosis and classification of liver hydatid cysts is based on imaging modalities mainly ultrasonography. MRI with MRCP is the important modality for both diagnosis and the search of possible communication between liver hydatid cysts and the biliary system. These modalities are widely used for the diagnosis and classification of the disease. In the hydatid cyst community, WHO classification is gaining more popularity over the conventional Gharbi system as it reflects the natural history of the cysts better and gives us a chance to make differential diagnosis between the active and inactive subtypes. Despite all the advancements in CT and MRI technology, ultrasonography is still the main workhorse for the classification of hydatid liver disease and widely employed worldwide both in diagnosis and classification.
There are four management options for the treatment of liver hyatid cysts. These include medical treatment, surgery, percutaneous treatment and wait and watch approach.
The results of medical management with mebandazole or albendazole were disappointing, based on the results in the last four decades and medical treatment only does not appear to be viable option.
Surgery is the conventional treatment of liver hydatid cysts. However, surgery is not a flawless approach with not insignificant rates of mortality, morbidity, postoperative recurrence and long period of hospital stay. The morbidity and mortality rates of surgery range between 12.5% and 80% and 0% and 6.3%, respectively. Post-surgical hospital stay is also highly variable, with an average of 14 days for non-complicated cases while it could go up to 30 days for complicated cases. Postsurgical recurrence rates also vary among the published series, depending on different parameters used, with a reported rate of 6.3% in a meta-analysis published in 2002.
Fig 1A. Ultrasound image demonstrates a CE 3b hydatid cyst located on caudate lobe of the liver.
Three main techniques have been described in the percutaneous treatment of liver hydatid cysts.
Described by Ben- Amour et al in 1986, PAIR is an abbreviation which stands for puncture, aspiration of cyst content, injection of hypertonic saline solution, and re-aspiration of all cyst fluid.
This technique is based on using hypertonic saline and alcohol, in a sequential manner, and was first described by our group in an experimental animal study in 1993. It is mainly a modification of the PAIR technique. In this technique, a 6F pig-tail catheter is placed into the cavity, with imaging guidance, by using modified Seldinger technique after the first three steps of the PAIR technique. The cavity is then washed by hypertonic saline and all the cystic cavity content is aspirated from the cavity through the catheter. The catheter is, finally, fixed to the skin and left to free drainage for 24 hours. When the catheter output is less than 10cc, a cystogram through the catheter is performed. In the absence of any biliary communication at the cystogram, 95% absolute alcohol is injected into the cavity (the alcohol amount injected is around 25– 35% of the cyst volume). After a dwelling time of 20 minutes, the injected absolute alcohol is re-aspirated and the catheter is withdrawn.
Modified catheterisation technique (MoCaT)
Again first defined by our group in 2007, in this technique, a 14F catheter is placed into the cavity, using a standard Seldinger technique, to evacuate all the cyst content (including fluid, daughter vesicles and degenerated membranes). The cavity is then rigorously cleansed with isotonic saline (%0.9 NaCl) with an irrigation technique which was referred to as “effective and aggressive irrigation”. Before the withdrawal of the catheter, sclerosis of the cavity by alcohol is performed.
Fig 1B. Fluoroscopy images show the first puncture and insertion of the 14F pig-tail catheter. The cyst cavity appears like a bunch of grapes.
Indications for percutaneous treatment
The imaging findings are the main indicators for maintaining the treatment plan of hydatid liver cysts. Percutaneous treatment should be based on a stage-specific approach and there is no “one-size-fits-all” approach in hydatid liver disease. Based on the WHO classification the PAIR or catheterisation technique are used for CE1 lesions, while, catheterization or MoCaT is used for CE2 lesions. As for CE 3 lesions, PAIR or Catheterization technique can be used for CE 3a lesions and CE 3b is mainly treated with MoCaT. Patients with CE 4 and CE 5 should be placed on yearly sonographic follow-up. This management approach may be defined as wait and watch approach as no active intervention is indicated in these patients. For the hydatid liver cysts having an abnormal communication with the biliary system, peritoneum or pleura, surgery is the optimal treatment approach.
What happens after percutaneous treatment?
An experimental animal study, conducted on sheep, revealed that macroscopic and microscopic findings, six months after percutaneous treatment, were in keeping with the findings visualised on follow-up ultrasound examinations. In this study, healing criteria were defined as reduction in size and volume of the cyst with thickening and irregularity of the cyst wall progressing to the gradual solidification and, finally, pseudotumour appearance.
Considering the number of percutaneously treated patients, the reported mortality rate is about 0.05%. Dissemination of the cyst content to the abdomen after percutaneous treatment was not reported in the reported patient cohorts. Among the major complications are: superinfection of the cyst cavity, cystobiliary communication and severe anaphylactic reaction. The overall reported rate of major complications is about 10%. Minor complications such as urticaria, severe itching and hypotension can easily be handled. Some patients may develop fever, not exceeding 38.5ºC, after the procedure that is mostly self-limiting. Recurrence rate varies and is reported to be between 0-4%. As for the duration of the hospital stay, the reported time period is between 2.5-4.2 days.
Percutaneous treatment of hydatid liver disease is an effective and safe approach with an impressive safety profile and effectiveness. Percutaneous treatment is associated with lower complication and recurrence rates and shorter hospital stay. Based on the scientific data and evidence, this approach should be considered first in these patients.
Okan Akhan is professor of Radiology, Hacettepe University, School of Medicine, Department of Radiology, Ankara, Turkey. He has reported no disclosures pertaining to the article