Answer for BIR CoW 17 Aug 2025
Hydatid cyst disease
Findings
Peripherally enhancing well defined large T2 hyperintense cystic lesion with multiple well defined non enhancing T2 hyperintense cystic lesions of varying sizes in subcutaneous and intermuscular plane of anteromedial aspect of left thigh showing multiple foci of blooming and no diffusion restriction -The lesion is compressing the adductor compartment muscles (adductor Magnus, adductor brevis and rectus femoris) - Features suggestive of hydatid cystic disease
Discussion
Hydatid Cyst Types
Common Locations
Cyst Structure
Radiographic Features
Classic Hydatid Signs
Unruptured Cyst
References: Pedrosa I, Saíz A, Arrazola J, Ferreirós J, Pedrosa C. Hydatid Disease: Radiologic and Pathologic Features and Complications. Radiographics. 2000;20(3):795-817. doi:10.1148/radiographics.20.3.g00ma06795 - Pubmed Polat P, Kantarci M, Alper F, Suma S, Koruyucu M, Okur A. Hydatid Disease from Head to Toe. Radiographics. 2003;23(2):475-94; quiz 536. doi:10.1148/rg.232025704 - Pubmed Eckert J & Deplazes P. Biological, Epidemiological, and Clinical Aspects of Echinococcosis, a Zoonosis of Increasing Concern. Clin Microbiol Rev. 2004;17(1):107-35. doi:10.1128/CMR.17.1.107-135.2004 - Pubmed
Findings
Peripherally enhancing well defined large T2 hyperintense cystic lesion with multiple well defined non enhancing T2 hyperintense cystic lesions of varying sizes in subcutaneous and intermuscular plane of anteromedial aspect of left thigh showing multiple foci of blooming and no diffusion restriction -The lesion is compressing the adductor compartment muscles (adductor Magnus, adductor brevis and rectus femoris) - Features suggestive of hydatid cystic disease
Discussion
Hydatid Cyst Types
- Cystic echinococcosis – most common
- Alveolar echinococcosis
Common Locations
- Liver – 75%
- Lung – 15%
- Spleen, kidney, CNS, musculoskeletal system
Cyst Structure
- Pericyst – dense fibrous capsule
- Exocyst
- Endocyst – germinal layer (produces daughter cysts internally, laminated membrane externally)
Radiographic Features
- Plain radiograph: Look for calcifications
- Ultrasound: Investigation of choice
- MRI: Defines disease extent
- T1: Hypointense
- T2: Hyperintense
- DWI: Variable
Classic Hydatid Signs
Unruptured Cyst
- Honeycomb / spoke-wheel / rosette / racemose pattern: Multivesicular mother cyst with daughter cysts
- Double line sign: Unilocular cyst with double-layer wall
- Serpent sign: Wavy membranes inside cyst
- Spin (whirl) sign: Twisting membranes
- Ball of wool (yarn / congealed water lily) sign: Solid conglomeration of collapsed membranes
- Crescent sign: Air between pericyst and endocyst → crescent rim of air
- Inverted crescent sign: Air at lower edge of cyst
- Cumbo sign (onion peel / double arch): Curvilinear membrane outlined by air inside and outside
- Water lily (camalote) sign: Folded floating membranes
- Empty cyst sign: Air-filled cavity after expectoration of membranes & fluid
References: Pedrosa I, Saíz A, Arrazola J, Ferreirós J, Pedrosa C. Hydatid Disease: Radiologic and Pathologic Features and Complications. Radiographics. 2000;20(3):795-817. doi:10.1148/radiographics.20.3.g00ma06795 - Pubmed Polat P, Kantarci M, Alper F, Suma S, Koruyucu M, Okur A. Hydatid Disease from Head to Toe. Radiographics. 2003;23(2):475-94; quiz 536. doi:10.1148/rg.232025704 - Pubmed Eckert J & Deplazes P. Biological, Epidemiological, and Clinical Aspects of Echinococcosis, a Zoonosis of Increasing Concern. Clin Microbiol Rev. 2004;17(1):107-35. doi:10.1128/CMR.17.1.107-135.2004 - Pubmed
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!