Overview
Definition:
A hydatid cyst of the liver is a parasitic cyst caused by the larval stage of the cestode Echinococcus granulosus, which resides in the small intestine of definitive hosts like dogs
Humans are intermediate hosts, and the liver is the most common organ affected, representing up to 70% of all hydatid cysts
These cysts are typically unilocular, with a germinal layer, laminated membrane, and protoscolices, surrounded by an adventitial layer (pericyst) formed by host tissue.
Epidemiology:
Hydatid disease is endemic in sheep-raising regions, including the Mediterranean, Middle East, South America, Africa, and parts of Central Asia
India, particularly rural areas with close contact with dogs and livestock, also reports cases
Incidence varies geographically but can be significant in endemic zones
Affects all age groups, but more common in those aged 20-50 years, with a slight female predominance.
Clinical Significance:
Liver hydatid cysts can range from asymptomatic incidental findings to life-threatening conditions due to complications like rupture, infection, or biliary obstruction
Understanding the appropriate management strategy, balancing minimally invasive techniques with definitive surgical excision, is crucial for patient outcomes and preventing recurrence or anaphylaxis.
Clinical Presentation
Symptoms:
Many asymptomatic cases detected incidentally on imaging
When symptomatic: Abdominal pain, typically dull ache, in the right upper quadrant
Hepatomegaly
Nausea and vomiting
Jaundice if cysts obstruct biliary ducts
Cough and dyspnea if cysts are large and press on the diaphragm or rupture into the lung
Fever and abdominal tenderness may suggest secondary infection
Anaphylactic reaction can occur with cyst rupture.
Signs:
Palpable hepatomegaly, sometimes with a smooth, firm mass
Tenderness on palpation of the liver
Signs of obstructive jaundice (icterus, pale stools, dark urine) if biliary involvement
Signs of anaphylaxis (urticaria, angioedema, bronchospasm, hypotension) if cyst rupture occurs.
Diagnostic Criteria:
Diagnosis is typically based on a combination of imaging, serology, and, if performed, cyst fluid analysis
Clinical suspicion in endemic areas is key
WHO Informal Working Group on Echinococcosis (GIDEON) classification helps stage cysts based on imaging features (e.g., CE1-CE5 stages).
Diagnostic Approach
History Taking:
Detailed history of residence in or travel to endemic areas
History of contact with dogs, particularly sheepdogs
Dietary habits (consumption of raw or undercooked offal)
Past history of hydatid disease or surgery
Gradual onset of abdominal symptoms, pain characteristics, associated symptoms like cough, jaundice, or fever
Any history of trauma to the abdomen.
Physical Examination:
Abdominal examination for hepatomegaly, assessing size, consistency, and tenderness
Palpation for masses
Auscultation for bowel sounds and any adventitious sounds
Assess for jaundice, ascites, or signs of portal hypertension
If rupture suspected, assess for signs of anaphylaxis.
Investigations:
Imaging: Ultrasound (USG) is the initial modality of choice, showing characteristic features like cystic lesions, daughter cysts (scolices), and cyst wall calcification
CT scan provides better anatomical detail and helps assess for complications and involvement of adjacent structures
MRI may be useful for complex cases or to delineate cyst contents and vascularity
Serology: Enzyme-linked immunosorbent assay (ELISA) for detecting specific antibodies against Echinococcus antigens (e.g., Em18, Em2)
High sensitivity but can have cross-reactivity
Performed in conjunction with imaging
Cyst fluid aspiration is generally contraindicated due to risk of anaphylaxis, but if done for diagnostic purposes (e.g., PCR), it can confirm the diagnosis
Complete Blood Count (CBC) may show eosinophilia, though not always present.
Differential Diagnosis:
Other liver cysts: Simple cysts, polycystic liver disease
Abscesses: Pyogenic or amoebic liver abscesses
Tumors: Hepatocellular carcinoma, cholangiocarcinoma, liver metastases (especially cystic metastases)
Benign tumors: Hepatic adenoma, hemangioma
Other parasitic infections: Cysticercosis, fascioliasis.
Management
Initial Management:
Asymptomatic cysts are managed expectantly or with conservative measures
Symptomatic cysts, complicated cysts, or large cysts require definitive treatment
All patients with suspected hydatid disease should be screened for anaphylaxis risk and managed accordingly
Pre-treatment with anthelmintics (e.g., albendazole 400 mg BID for 1-3 months) is recommended before invasive procedures to reduce scolicidal load and recurrence, particularly for PAIR.
Medical Management:
Anthelmintic therapy (albendazole or mebendazole) is primarily used as an adjunct to invasive procedures or for inoperable cases
It does not typically cure established hydatid cysts but can reduce cyst size and prevent growth
Long-term therapy may be required
It is also used for prophylaxis against recurrence post-surgery in some protocols.
Surgical Management:
The choice between PAIR (Puncture, Aspiration, Re-injection, and further Aspiration) and surgical excision (pericystectomy or hepatectomy) depends on cyst size, location, number, stage, presence of complications, and patient factors
PAIR: A minimally invasive technique, often guided by ultrasound or CT
Indicated for uncomplicated, intact cysts, usually >3 cm
Pre-medication with albendazole is essential
Complications include anaphylaxis, secondary infection, and leakage
Pericystectomy: Enucleation of the intact cyst with its pericystic layer
Preferred for smaller to medium-sized cysts, especially in superficial locations
Minimal liver resection is involved
Hepatectomy: Reserved for very large cysts involving major vascular or biliary structures, or when multiple cysts are present within a lobe, or for complicated cases like infected cysts or those with biliary communication that cannot be managed otherwise
It involves removing a portion of the liver parenchyma.
Supportive Care:
Postoperative care for PAIR involves close monitoring for signs of anaphylaxis and infection
Postoperative care for surgical excision includes standard post-laparotomy/laparoscopic care, pain management, wound care, fluid balance, and early mobilization
Anthelmintic therapy is often continued post-operatively to prevent recurrence
Nutritional support is important for recovery.
Complications
Early Complications:
Anaphylactic shock following cyst rupture or aspiration (most feared complication)
Secondary bacterial infection of the cyst
Hemorrhage from the cyst or during surgery
Biliary peritonitis if cyst communicates with biliary tree
Worsening jaundice due to biliary obstruction
Pneumothorax/hemothorax if cyst ruptures into pleura/lung.
Late Complications:
Recurrence of hydatid disease
Liver abscess formation
Chronic biliary obstruction leading to cholangitis or liver cirrhosis
Hepatic dysfunction
Metastatic hydatid disease (rare).
Prevention Strategies:
Strict adherence to PAIR protocols with pre-medication, careful aspiration techniques, and use of scolicidal agents in the aspirate if possible
Thorough surgical excision of the entire cyst with pericyst
Careful intraoperative management to prevent spillage
Postoperative anthelmintic therapy
Public health measures to control Echinococcus transmission (deworming dogs, safe slaughter practices).
Prognosis
Factors Affecting Prognosis:
Size, number, and location of cysts
Presence and severity of complications (rupture, infection, biliary involvement)
Adherence to treatment protocols
Host immune status
Promptness and appropriateness of treatment
The effectiveness of PAIR versus surgical intervention for specific cyst characteristics.
Outcomes:
With appropriate management, the prognosis for liver hydatid cysts is generally good
Asymptomatic or uncomplicated cysts treated effectively have excellent outcomes
Complicated cysts or those with significant rupture carry a higher risk of morbidity
Recurrence rates vary depending on the treatment modality and completeness of excision, typically ranging from 2-20%.
Follow Up:
Long-term follow-up is essential, typically with ultrasound and serology every 6-12 months for several years (5-10 years) post-treatment, especially after PAIR or in cases with high recurrence risk
This is to detect any recurrence or new cyst formation.
Key Points
Exam Focus:
The primary goal is to understand the indications for PAIR versus surgical excision (pericystectomy/hepatectomy)
Remember PAIR for uncomplicated, intact, suitable cysts
Surgery for complicated, very large, or multiple cysts
Anaphylaxis is the major risk of PAIR and cyst rupture
Albendazole pre-treatment is crucial for PAIR.
Clinical Pearls:
Always inquire about travel/residence in endemic areas for hydatid disease
Ultrasound is the first-line imaging
Consider serology as supportive
NEVER aspirate an intact hydatid cyst without scolicidal agents and immediate operative backup due to anaphylaxis risk
Thorough pericyst removal during surgery minimizes recurrence
Post-operative albendazole is standard of care.
Common Mistakes:
Performing PAIR without adequate scolicidal agent precautions or scolicidal agent in the aspirate
Incomplete pericystectomy leading to recurrence
Neglecting to prescribe postoperative albendazole
Misinterpreting imaging or serology leading to delayed or incorrect treatment
Operating on an infected cyst without appropriate drainage and antibiotic therapy first.