A 38-year-old woman comes to the office due to fatty food intolerance. On examination, her vital signs are normal, and she has mild right upper quadrant abdominal tenderness. An ultrasonogram of the abdomen reveals multiple gallstones with no evidence of cholecystitis and an ill-defined intrahepatic cyst with a thick wall. A CT of the abdomen is performed and reveals a well-defined cyst with eggshell calcification. Past medical history is insignificant. She is not taking any drugs and has never had surgery. The patient has not travelled outside the United States. She has had 2 pet dogs at home for 10 years. Her parents emigrated from Peru many years ago. What is the most likely etiology for the intrahepatic cyst in this patient?

Question

A 38-year-old woman comes to the office due to fatty food intolerance.  On examination, her vital signs are normal, and she has mild right upper quadrant abdominal tenderness.  An ultrasonogram of the abdomen reveals multiple gallstones with no evidence of cholecystitis and an ill-defined intrahepatic cyst with a thick wall.  A CT of the abdomen is performed and reveals a well-defined cyst with eggshell calcification.  Past medical history is insignificant.  She is not taking any drugs and has never had surgery.  The patient has not travelled outside the United States.  She has had 2 pet dogs at home for 10 years.  Her parents emigrated from Peru many years ago.  What is the most likely etiology for the intrahepatic cyst in this patient?

Quizplus · Accepted Answer

This patient has a hydatid cyst due to Echinococcus granulosus. Humans contract the infection from close and intimate contact with dogs, which are the definitive host in the tapeworm's lifecycle. E granulosus typically causes unilocular cystic lesions that can occur in any organ (eg, liver, lung, muscle, bone); smaller daughter cysts may be present. Multiple lesions are usually associated with E multilocularis (rather than E granulosus) infection. Most hydatid cysts are diagnosed incidentally when patients are being evaluated for other problems (eg, fatty food intolerance likely from cholelithiasis in this patient). However, these cysts can cause symptoms due to compression on surrounding tissues. Imaging techniques and serologic testing can be used for diagnosis. "Eggshell" calcification of a hepatic cyst on CT scan is highly suggestive of a hydatid cyst. Treatment is generally surgical resection under the cover of albendazole. In some situations, aspiration can be performed, although there is a risk of anaphylactic shock due to cyst content spillage. "Eggshell" calcification (Choice A) Patients with amebic liver abscess (most common extraintestinal manifestation of amebiasis) usually have fever and right upper quadrant pain that can develop within weeks of intestinal amebiasis. Eggshell calcifications on CT scan would be unusual. (Choice B) Cysticercosis is due to infection with Taenia solium and generally presents as cysts in the brain or muscle. (Choice D) Pyogenic liver abscesses generally develop following surgery, gastrointestinal infection, or acute appendicitis. Patients typically have extreme pain, high fevers, and leukocytosis. (Choice E) Simple hepatic cysts are believed to be congenital. The pathophysiology is related to fluid secretion by the epithelial lining. Patients with simple hepatic cysts that cause symptoms usually report dull right upper quadrant pain, abdominal bloating, or early satiety. However, these cysts will not show calcification on CT scan. Educational objective: In humans, hepatic hydatid cysts are due to infection with Echinococcus granulosus. Dogs are the definitive host. A cystic hepatic lesion with eggshell calcification is highly suggestive of infection with this organism.

A 38-Year-Old Woman Comes to the Office Due to Fatty