This document summarizes information about hydatid cysts, which are caused by infection with the larval stage of the Echinococcus tapeworm. It describes the lifecycle of E. granulosus and how humans can become infected through contact with dog feces. Hydatid cysts most commonly form in the liver and lungs, and may grow slowly over many years without symptoms. Clinical features depend on the infected organ and size of cysts. Imaging tests and serology can help diagnose cysts, while treatment involves antiparasitic drugs, percutaneous drainage, or surgical removal based on cyst type and location. Close follow up is needed due to risk of recurrence.

1. Hydatid cyst
Pranjal Rokaya
Resident General Surgery
KIST MCTH
29th December, 2022

2. Outline

3. Echinococcal disease
• Caused by infection with larval stage of tapeworm Echinococcus.
• Belong to family taenidae.
• Two species most commoly cause disease in human:
a. E. granulosus : Cystic echinococcus (CE)
b. E. multilocularis : Alveolar echinococcus (AE)

4. Echinococcus granulosus
• Dog tapeworm
• Habitat: Duodenum and jejunum of dogs and
other canine carnivores.
• Small tapeworm (3-6 mm).
• Consists of scolex, short neck and strobila.
• Strobila composed of three segments.
• Adult worm lives for 6-30 months.

5. • Eggs
Indistinguishable from those of other Taenia species.
Contains embroyo with three pair of hooklets.
• Larval form
Found within hydatid cyst developing inside various organs of intermediate host.
Represents scolex of adult worm.
After entering definite host, scolex exvaginates and develops into adult worm.

6. Lifecycle of Echinococcus granulosus

8. …Life cycle
• Infection follows ingestion of eggs due to intimate handling of dogs or eating raw
food contaminated with dog faeces.
• Ova liberated from chinitous wall by gastric juice liberating embroyos which
penetrate intestinal wall and enter portal venules.
• Trapped in hepatic sinusoids where they eventually develop into hydatid cyst.
• Some embroyos pass liver, get trapped in pulmonary capillary.
• Few enter systemic circulation and get lodged in various organs.

9. Evolution of hydatid cyst
• Greek: Hydatis: Drop of water.
• At site of deposition, embryo develops into hollow cyst filled with fluid.
• Enlarges slowly and reaches diameter of 0.5-1 cm in 6 months.
• Evokes host repsonse leading to deposition of capsule around it.

10. …Evolution of cyst
• Cyst wall secreted by embroyo has three layers:
a. Pericyst: Consists of fibroblastic proliferation,
mononuclear cells, eosinophils and giant cells;
eventually developing capsule.
b. Ectocyst: Composed of acellular, hyaline
material.
c. Endocyst: Germinal layer consisting of number
of nuclei; gives rise to brood capsule and hydatid
fluid.

11. …Evolution of cyst
• Hydatid fluid
Contains NaCl, sodium sulfate and salts of succinic acid.
Highly antigenic; liberation into circulation: eosinophilia
and even anaphylaxis.
• Brood capsule
Found at hydatid sand; originated from endocyst, gives
rise to protoscolices.
 Inside mature cyst, daughter and granddaughter cyst
may develop often over 20 years or more.

12. Organs involved
Liver : 66 %
Lungs : 25%
Brain, muscles, spleen, bones, pancreas.
• Single organ involvement in 85-90 % cases.

13. Clinical features
• Initial phase always asymptomatic.
• Many infections acquired in childhood but don’t cause symtoms until adulthood.
• 50% of detected cases in asymptomatic patients.
• Clinical feature depends upon site of cyst and their size.

14. Clinical features
a. Liver
Right lobe in 60-85% cases; symptoms unusual with cyst < 10 cm.
Hepatomegaly a/w RUQ pain, nausea and vomitting.
In 1/4th cases, cyst ruptures into biliary tree producing biliary colic, obstructive
jaundice, cholangitis and or pancreatitis.
Pressure effect: Cholestatis, portal hypertension, venous obstruction.
Rupture into peritoneum: peritonitis; transdiaphramatically: pulmonary hydatosis or
bronchial fistula.

15. b. Lungs
60% affects the right lung; 50-60% involve lower lobe.
• Cough (53-62%)
• Chest pain (49-91%)
• Dyspnea (10-70%)
• Hempotysis (12-21%)
Cyst rupture into pleural cavity: Pneumothorax, effusion or empyema.
Bacterial infection: Pulmonary abscess.

16. Other organs involvement
Heart: Mechanical rupture with widespread dissemination or tamponade.
CNS: Seizures, signs of raised ICP.
Kidneys: Hematuria , bilateral flank pain: glomerulonephritis leading to nephrotic
syndrome.
Bones: Asymptomatic until pathological fracture develops.

17. Complications
• Anaphylaxis
• Rupture of the cyst
• Obstructive jaundice
• Infection
• Calcification
• Liver failure

18. Investigations
Imaging Serology

19. Imaging
1. Ultrasonography
Sensitivity: 90-95%
Most common appearance: Anechoic, smooth, round cyst difficult to distinguish
from benign cyst.
In presence of liver cyst membrane, mixed echoes confused with abscess or
neoplasm.
Daughter cyst: Internal septations seen.

20. Classification based on USG
Gharbi classification
Type 1 Consists of pure fluid
Type 2 Fluid collection with split wall
Type 3 Contains daughter cysts (with
or without degenerated
material.
Type 4 Heteogenous echo pattern
Type 5 Calcified wall

21. WHO classification of hydatid cyst
WHO stage Description Stage
CE1 Unilocular, unechoic cystic lesion Active
CE2 Multiseptated cyst Active
CE3a Cyst with detatched membrane Transitional
CE3b Cyst with daughter cyst in solid matrix Transitional
CE4 Cyst with heterogenous hypo/hyperechoic
content; no daughter cysts
Inactive
CE5 Solid plus calcified wall Inactive

23. A non-calcified liver cyst with
with floating layers of germinal
membrane
Hydatid daughter cyst

24. Imaging
2. Computed tomography
Sensitivity: 95-100%
Best mode to determine number, size and anatomical
location of cysts.
Better for detection of extrahepatic cysts compared to
USG.
Used for monitoring lesions during therapy and detect
recurrence.

25. Imaging
3. MRI
No major advntage over CT for evaluation of abdominal or pulmonary cysts,
except in defining intra and extrahepatic venous system.
May delineate cyst capsule better than CT and better at diagnosing complications
(infection or biliary communication).
Usually not required, neither cost effective.

26. Serologic tests
Site of lesion Sensitivity of serologic tests
Liver a. IgG ELISA : 80-90 %
b. IgE ELISA. : 82-92%
c. Latex agglutination. : 65-75%
d. Hemagglutinin. : 80-90%
e. Immunoblot. : 80 %
Lung a. IgG ELISA : 60-85%
b. IgE ELISA. : 45-70%
c. Latex agglutination. : 50-70%
d. Hemagglutinaton. : 50-70%
e. Immunoblot. : 55-70%

27. Serologic tests
• Two antigens used in serologic tests: antigen 5 and antigen B.
• Utility of serology improved with combination of test or
sequential testing.
• No correlation between results and number or size of cyst.
• Negative test doesn’t rule out the disease.
• Less likely to be (+): cysts intact, calcified or noviable.

28. Interventional procedure
• In absence of (+) serology, percutaneous aspiration
or biopsy may be required for confirmation.
• Aspiration peformed under USG or CT guidance.
• ERCP may be required to evaluate biliary
involvement.
• May demonstrate hydatid membrane within
duodenum or impacted im pappila.

29. Differential diagnosis
a. Simple benign cyst
b. Hemangioma
c. Hepatocellular carcinoma
d. Abscess
e. Tuberculosis

30. Treatment
Antiparasitic
therapy
Percutaneous
aspiration and
instillation of
scolicidal
agent
Surgical
resection

31. Treatment based on WHO classification

32. Antiparasitic therapy
• Albendazole: Primary antiparasitic agent.
• Poorly absorbed; ideally ingested with fatty meal to increase bioavailability.
• Effective alone for cysts with single compartment and diameter <5 cm. (CE1,
CE3a).
• Drug t/t alone for multiple liver cyst <5 cm, cysts deep inside liver parenchyma
and intraperitoneal cyst.
• Definite therapy: one to three months

33. Adjunctive therapy
• Drug useful adjunct to surgery and percutaneous t/t.
• Perioperative drug therapy reduces recurrence by inactivatig protoscolices; aslo
softens cyst facilitating removal.
• Treatment initiated at least 4 days prior to surgery and continued at least one
month (albendazole) or three months (mebendazole) following surgery.
• Drug also required after spontaneous cyst rupture.

34. Mechanism of action

35. Percutaneous treatment (PAIR)
• Indications
Inoperable patients.
Pts. who refuse surgery.
CE1 and CE3a cyst more than 5 cm.
In pregnant women, children <5yrs.
Relapse after medical therapy or surgical therapy (w/o daughter cysts).

36. PAIR
P : Puncture of cyst under imaging guidance.
A : Aspiration of the cyst contents.
I : Instillation of the scolicidal agent in the cyst cavity.
R : Respiration.

37. Contraindication of PAIR
• Cysts with nondrainable solid material.
• Superficial cysts at risk of rupture into abdominal cavity.
• Cysts that have rupture into peritoneum.
• Cysts with biliary communication.
• Inactive or calcified cysts.

38. Modified catheterization techniques
• Large bore catheters and cutting devices used together to remove entire
endocyst and daughter cysts.
• Appropriate for:
 Cysts difficult to drain via PAIR.
 Stage CE2 and CE3b, which have many compartments, and commonly relapse
after PAIR.

39. Surgical treatment
• Indications
a. Complicated cysts
i. Ruptured cyst. ii. Cysts with biliary fistula
iii. Cysts compressing vital structure. iv. Cysts with secondary infection/hemorrhage
b. Cysts with many daughter vesicles not suitable for percutaneous t/t.
c. Cysts more than 10 cm.
d. Extrahepatic disease( lung, bone, brain, kidney, spleen).

40. Surgical treatment
• Goal is to evacuate the cyst and obliterating residual cavity.
• Effort made to avoid fluid spillage. (3-6 months albendazole)
• Different techniques:
Removal of intact cyst if feasible.
Cyst opened, sterilised, contents evacuated and pericyst removed.
 Laying open of cyst cavity w/o removing pericyst.
• Cyst excision followed by omentoplasty a/w lowest complication rates.

41. Surgical treatment
• Surgical field should be protected with pads soaked with scolicides.
• Scolicidal agents not used in case of biliary communication to prevent risk of
sclerosing cholangitis or pancreatitis.
No RCTs performed comparing laparoscopic approach vs open.
Laparoscopy may be a/w increased risk of spillage.
Exclusion criteria for laparoscopy: a. Deep intraparenchymal cysts
b. Posterior cysts close to venacava. c. Presence of >3 cysts with calcification.

44. Follow up
• Can relapse years after treatment.
• F/U consists of USG or other imaging at 3-6 months intervals until findings are
stable; followed by yearly monitoring.
• F/U up to 5 years may be warranted.

45. F/U : USG
• USG findings that correlate with effective therapy:
a. Complete cyst disappearance.
b. Reduction in cyst size and volume.
c. Increase in propotion of solid component of cyst.
d. Thickening and irregularity of cyst wall.
e. Within multivesicular cysts, reduction in size and/or number of daughter cysts.

46. F/U: Serology
• Serologic titres usually fall by 1 to 2 years following surgery and rise again in
setting of recurrence.
• Antibodies may remain elevated many years after succesful cyst removal.

47. Prevention
Ensuring pet dogs don’t eat animal carcass.
Periodic deworming of pet dogs.
Euthanization of infected dogs.
Washing hands after touching dogs; avoiding kissing pet dogs.

48. References
• Bailey and Love, 26th edition.
• Swartz texbook of surgery, 11th edition.
• Sabiston textbook of surgery, 21st edition.

49. Thank You.