More than 80–90% of hydatid cysts occur in the liver, lungs, or both, However unusual location of HD have been rarely reported[1]. Furthermore, the diagnosis of hydatid cysts in unusual sites is difficult, and differential diagnosis is always posed[2].
The clinical symptomatology of HD depends on the size, the site, and the extent of the lesion[2]. In fact, Extrahepatic hydatid cysts usually remain asymptomatic for years[3].
Radiological imaging plays a crucial role in the identification and diagnosis of HD. Ultrasonography (USG) is the first line radiological exam, it is useful for the diagnosis by detecting cystic membrane, septa and hydatid sand[1]. CT scan represents also a routine modality for the diagnosis of HD from other differential diagnosis, and it is useful when suspecting peritoneal seedling. CT scan findings show a “spoke wheel” pattern or a water lily sign, or multiple cystic lesions or with calcification in the peritoneum[3].
Serological tests are useful for the diagnosis, enzyme-linked immunosorbent assay (ELISA) is the widely available serological technique to diagnose the hydatid disease[3].
Hydatid cyst can affect any organ in the body but is often located in the liver and lungs[2], [4]. Because of The liver is the first sieve to encounter portal flow, most larvae are trapped and cysts begin to grow. Larvae that successfully penetrate the liver barrier proceed to the lungs, where they develop into hydatid cysts. In rare cases (10–20%), they pass through these filters and enter the systemic circulation getting in any tissues[4]. As per the existing literature, the prevalent sites included the CNS, musculoskeletal system, heart, and kidney. Nevertheless, infrequently documented sites encompass the spleen, pancreas, appendix, thyroid, salivary gland, adrenal gland, breast, and ovary. [4].
Spleen localization of the hydatid cyst is uncommon, especially when the parasite primarily infects this organ. [5]. This scenario arises in around 2% of instances where the parasite bypasses hepatic and pulmonary filters. [6], [7], However, it stands as the most common extrahepatic site for hydatid cysts. [8]. Diagnosing splenic hydatid cysts is typically a complex task[6]. Indeed, the symptoms are often unclear, and clinical indicators are not sufficient to establish the diagnosis [8]. Immunological findings and serology can provide valuable assistance in distinguishing between various types of splenic cysts [8]. However, imaging findings, including ultrasound (US), CT scan, and MRI, are more instrumental in confirming the diagnosis of splenic hydatid cysts. [8].
Nonetheless, the peritoneal occurrence of hydatid cysts, whether originating directly or as a secondary manifestation, is a rare but noteworthy aspect of the disease, constituting a significant proportion (around 13%)[6]. Secondary peritoneal hydatid cysts typically arise when a primary cyst in the liver or spleen ruptures. Conversely, primary peritoneal hydatid cysts are observed in only 2% of all abdominal hydatid cyst cases [6].
Pelvic hydatid disease is a rare occurrence, manifesting in approximately 2.25% of cases [7]. The presence of a primary pelvic hydatid cyst is exceedingly rare, typically characterized by pressure symptoms affecting neighboring organs [5].
However, the incidence of hydatid cysts in the ovary is relatively infrequent, varying between 0.2% and 2.25% [7]. Ovarian hydatid disease often arises following the rupture of liver hydatid cysts into the peritoneal cavity, leading to the spread of the parasite within the pelvic cavity [9].
Renal hydatid cysts are likewise uncommon, accounting for only 1–3% of cases[7]. They are documented as a more frequent occurrence compared to other locations, following the liver and lungs in the literature [5]. Furthermore, retroperitoneal hydatid disease is an exceedingly rare occurrence[8]
Consequently, hydatid cysts in the pancreas are an exceptionally rare scenario, with reported occurrences ranging from 0.5–0.8% of cases [7]. he presence of hydatid cysts in the pancreas poses challenges both in terms of diagnosis and treatment [5].
The occurrence of a hydatid cyst in the gallbladder is highly uncommon, with an incidence of approximately 0.4% [5].
Instances of inguinal canal hydatid disease presenting as inguinal hernia are exceptionally rare, with the literature reporting only five cases [5]. Likewise, abdominal wall hydatid cysts are an infrequent phenomenon, with only five reported cases in the literature [5].
The management of extrahepatic hydatid cysts is contingent upon their size and location [10]. For smaller cysts, medical treatment involving antihelminthic drugs is recommended. However, surgery becomes necessary for symptomatic and larger cysts. The preferred approach is total cyst removal[10]. In the case of splenic hydatid cysts, the management approach is subject to discussion: some advocate for conservative surgical options such as partial splenectomy or cyst drainage [8]. For abdominal wall hydatid disease, treatment entails complete excision, and in some instances, abdominal reconstruction employing prosthetic materials may be performed [8].