CT Case 077
A 23-year-old woman presents with 3 weeks of right upper quadrant (RUQ) pain associated with early satiety.
The patient has no significant past medical history. She was born in Iraq and migrated to Australia from Syria 2 years prior to presentation.
Preliminary blood results demonstrate moderate liver function test (LFT) derangement
Describe and interpret the CT images
The case demonstrates classical appearance of a hepatic hydatid cyst. There is a well-defined rounded lesion in right lobe of liver with multiple small daughter cysts within.
The fluid in the cysts can be of variable density depending on the proteinaceous contents (more protein = more dense).
The thick internal septae can give a “spoke wheel” appearance as in this case.
Curvilinear calcifications can sometimes be seen, when present this represents the inactive stage of the disease.
Clinical Pearls
The clinical picture is most consistent with hydatid cysts. This diagnosis was confirmed with positive hydatid serology.
Hydatid diseaseis a parasitic zoonosis, it is caused by the larval stages of the Echinococcus tapeworm.
Echinococcus granulosus is the most common species of Echinococcus. While it can result in hydatid cyst formation anywhere in the body, the most commonly affected organ is the liver (76% of cases), followed by lung (15%) and spleen (5%).
The typical appearance is of a spherical, fibrous-rimmed cyst with little, if any, surrounding host reaction. Classically there is a large ‘parent cyst’ which contains numerus peripheral ‘daughter cysts’.
E. granulosus is found worldwide, however the highest rates of infection are seen in the Mediterranean and Middle Eastern regions, North Africa and South America.
Humans are infected by eating the eggs of the tapeworm E. granulosus, by either eating contaminated food or through contact with dogs.
The ingested embryos invade the intestinal mucosal wall, enter the portal circulation and develop cysts in the liver.
There are four treatment options available;
- Surgical excision
- PAIR (Puncture, Aspiration, Injection of protoscolicidal* agent and Re-aspiration)
- Anti-helminthic agent (e.g. albendazole, mebendazole)
- Observation only – for inactive and silent cysts
*Nb: A protoscolicidal agent is an agent which can kill a Scolex (the tapeworm head). Various agents are used such as hypertonic saline, ethyl alcohol, chlorhexidine hydrogen peroxide.
This patient was managed with anti-helminth treatment (Albendazole) followed by surgical cyst excision.
References
- Echinococcosis. CDC
- Polat P, Atamanalp SS. Hepatic hydatid disease: radiographics findings. Eurasian J Med. 2009 Apr;41(1):49-55.
TOP 100 CT SERIES
Sydney-based Emergency Physician (MBBS, FACEM) working at Liverpool Hospital. Passionate about education, trainees and travel. Special interests include radiology, orthopaedics and trauma. Creator of the Sydney Emergency XRay interpretation day (SEXI).
Provisional fellow in emergency radiology, Liverpool hospital, Sydney. Other areas of interest include paediatric and cardiac imaging.
Emergency Medicine Education Fellow at Liverpool Hospital NSW. MBBS (Hons) Monash University. Interests in indigenous health and medical education. When not in the emergency department, can most likely be found running up some mountain training for the next ultramarathon.
Dr Leon Lam FRANZCR MBBS BSci(Med). Clinical Radiologist and Senior Staff Specialist at Liverpool Hospital, Sydney