Daily Radiology Case

Explanation

The CT demonstrates a massive multiloculated cystic mass with peripherally arranged daughter cysts ("honeycomb appearance") and the claw sign of stretched residual renal parenchyma, diagnostic of a renal hydatid cyst caused by Echinococcus granulosus. Humans are accidental intermediate hosts infected by ingesting eggs shed by canine definitive hosts, with the liver and lungs acting as sequential filters that make isolated renal involvement rare. Management combines preoperative albendazole with surgical excision, taking great care to avoid spillage, which can precipitate anaphylaxis or peritoneal seeding with secondary echinococcosis.

Source: Bekele A, Renal hydatid cyst. Case study, Radiopaedia.org (Accessed on 27 Apr 2026) https://doi.org/10.53347/rID-234320

Hints

• A 16-year-old female presents with progressive, painless abdominal swelling that has been gradually enlarging over the past three years.
• On physical examination, a large, firm, non-tender mass is palpable in the right hemiabdomen, demonstrating ballotability that suggests a retroperitoneal origin.
• Further history reveals close, prolonged contact with sheep and herding dogs in a rural farming community, and serology returns positive for antibodies against a parasitic antigen.
• Axial contrast-enhanced CT shows a massive multiloculated cystic mass containing numerous peripherally arranged smaller cysts within a larger parent cyst, producing a characteristic "honeycomb" appearance with a thick wall and scattered mural calcifications.
• The residual right renal parenchyma is thinned, stretched, and displaced posteriorly around the mass, producing the classic "claw sign" that confirms its renal origin.
• Isolated involvement of this organ by this zoonotic cestode is uncommon (2–4%), as the liver and lungs are filtered first, and management requires surgical excision with meticulous technique to prevent the catastrophic complications of cyst rupture.