Discussion
Tapeworms from the Echinococcus family have been introduced since the 1950s as a pathogenic parasite for humans. Two important species of this parasite include E. granulosus and E. multilocularis , which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively, among which infection with CE is more common. The mature worm exists in the small intestine of carnivores, and the eggs are released via the animal’s feces and contaminate water and food. Food materials contaminated with Echinococcus eggs are swallowed by intermediate hosts, including herbivores, and the eggs enter the human body directly (contact with infected animals) or indirectly (eating contaminated food or water) and the larvae spread through the human body hematologically and via the lymphatic route (5,6).
This parasite is distributed all over the world, but the endemic areas include Oceania, China and the central regions of Asia, central and southern Russia, Middle East, Mediterranean regions, parts of Africa and North America (6). CE is considered an important parasitic disease in the world, and is an important concern for developing and low-income countries due to significant mortality and morbidity. According to the WHO report, this disease is one of the 17 important neglected parasitic diseases. More than one million people are infected annually and about 20 thousand people die due to the disease. Disability-adjusted life-years (DALYs) are estimated to be more than 800,000 years and the annual treatment cost is over 3 billion dollars (6,7). This disease usually occurs in the 40s and 50s and is slightly more common in women than men, and living in urban areas and contact with dogs and livestock bears a greater chance of infection (3). CE is usually asymptomatic and is usually found incidentally in unrelated examinations. Although in many cases, several diagnostic measures are used, CT scan is the gold standard for hydatid cyst diagnosis (8). Serological tests are only used to confirm the diagnosis, and negative test results do not rule out CE. It may take years from the time the parasite enters the human body until the symptoms develop, and the development of symptoms depends on the size of the cyst and its anatomical location (9). If symptoms develop, dull abdominal pain is the most common symptom. Usually, during CE disease, only one cyst is formed and multi-organ involvement is not common. The most common site for cyst formation is the liver, followed by the lungs. Involvement of the CNS, muscles, and spleen rarely occurs, and involvement of the peritoneum and omentum is extremely rare (3).
The presented patient was an elderly male living in the village with occasional contact with livestock, who presented with a complaint of vague abdominal pain and weight loss, as well as a history of colorectal cancer in the first degree family. Due to iron deficiency anemia and presence of red flag symptoms, preliminary investigations aimed to rule out malignancy. Although cystic lesions of the liver and spleen favoring hydatid disease were found in ultrasound, serology testing of hydatid cyst was negative. In addition to confirming the presence of a calcified liver cyst, the CT scan showed an enlarged spleen containing several cystic structures and evidence of extensive involvement of the omentum and peritoneum, which looked similar to metastatic lesions and peritoneal seeding. Therefore, we decided to perform a diagnostic laparoscopy for this patient, the result of which was the involvement of the peritoneum and omentum with hydatid disease.
In recent studies, patients with CE mostly had one cyst, and in a study conducted in 2020 on 501 CE patients over 15 years, the prevalence of peritoneal involvement was only 1% (3). Study results have shown that peritoneal hydatid cyst usually occurs secondary to trauma or abdominal surgery and due to the rupture of a liver cyst in the abdominal cavity. Despite this, the presented case had no history of abdominal surgery or blunt trauma to the abdomen. There are various hypotheses regarding the development of primary hydatid cyst in the peritoneal cavity, none of which have been proven. Although, it has been suggested that the localization of hydatid cyst in the peritoneum can be a result of the migration of the liver cyst through the blood and lymphatic circulation or the rupture of the adventitia without rupture of the cyst membrane (4).
The main approaches of treatment are medical treatment with anthelmintic drugs (usually Albendazole 10 mg/kg), surgery or both. The aim of treatment is to eliminate the cyst, minimize complications and prevent recurrence. In this regard, surgery is still the best therapeutic approach and will convey the best results if combined with medical treatment. Medical treatment is effective in stopping parasitic growth and is usually not enough alone. Isolated medical treatment is indicated when the patient is not a suitable candidate for surgery (10). In the patient in question, due to splenomegaly and the involvement of all parts of the spleen, splenectomy was performed, and in relation to the peritoneal and omental cysts, due to the high risk of perforation leading to peritonitis and anaphylactic shock, all parts involved with cysts were removed. Also, due to the calcification of the liver cyst, this cyst remained intact and the patient was prescribed oral Albendazole for 3 months.