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Hydatid Cyst

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A hydatid cyst is a fluid-filled sac caused by infection with the tapeworm Echinococcus, commonly affecting the liver and lungs.

What is the Hydatid cyst?

The hydatid cyst represents the larval stage of the infection with Echinococcus granulosus or Echinococcus multilocularis (tapeworms). The cyst appears as the result of the parasitic infestation with the above mentioned organisms. The number of people who are diagnosed with this condition has increased in the past years, due to the development of globalization (which has resulted in increased transcontinental transportation). There are two main types, meaning the cystic echinococcosis and the alveolar echinococcosis.

Epidemiology

Given the frequency of this condition, it can be assumed that this is a rare disease in the United States. There are only a few areas in the northern part of Alaska, where this condition is considered endemic. The northern part of Europe also sees very few cases of hydatid cysts. On the other hand, these are the areas that are considered to be endemic: Africa (south), New Zealand, Australia, Iceland, South America (south), Middle East and Mediterranean countries. Central Asia, with China at the top of the list, is also considered an endemic area for the hydatid cyst.

There is no race or sex predilection when it comes to the appearance of the hydatid cyst. However, the hydatid cyst is known to grow slowly – this is the reason why the diagnosis is rarely made during childhood or adolescence (the only situation when the diagnosis is made at that age is if the brain has been affected). The hydatid cyst is considered a disease that affects mainly young adults, with the average age for diagnosis varying between 30 and 40 years. On the other hand, older adults can suffer from this problem as well.

Physiopathology

As it was already mentioned, the hydatid cyst is actually the result of a zoonotic infection, with tapeworms that belong to the Echinococcus genus. Apart from the organisms that were presented in the paragraph above, there are other tapeworms that can lead to the appearance of this cyst – such as Echinococcus vogeli (this is however quite rare). One should remember that E. multilocularis is not a common parasite but it can lead to a serious infection, given its high virulence.

Symptoms of Hydatid Cyst

First of all, keep in mind that there are many patients who have a hydatid cyst but do not present any symptoms (even at an advanced age). There are a number of factors that influence the appearance of certain symptoms, such as: the parasite load, site where the tapeworm has made the infestation and also how big the cyst actually is

The hydatid cyst can appear at the site of any organ but the liver seems to be the organ most commonly involved. The lungs are also typically affected by such health problems. It is said that the liver and the lungs account for 90% of the cases.

When it comes to the cystic echinococcosis, it is important to remember that it takes a long time for the symptoms to become obvious (the only exception from that rule is when the parasite is found at the level of the brain or the eyes). It is known that the hydatid cysts produce symptoms when they are larger in size (over 5 cm diameter). Apart from the liver and the lungs, the following organs can be affected by the hydatid cyst: muscles, bones, kidneys, brain and spleen.

There are a number of symptoms that are actually caused by the pressure resulting from the hydatid cyst, such as:

  • Non-specific symptoms

    • Pain

    • Cough

    • Fever (low-grade)

    • Abdominal fullness sensation

  • More specific symptoms (the mass grows, thus pressing or obstructing a certain organ)

    • Jaundice and abdominal pain (liver)

    • Biliary colic, jaundice and urticaria (biliary rupture)

    • Hydatid membranes in the emesis or the stool (rarely)

    • Chronic cough, difficulties breathing, pleuritic or chest pain, coughing up blood (lungs)

    • Cystic membrane expectoration, sputum (intrabronchial rupture)

    • Confusion, reduced consciousness, vertigo, headaches, neurological deficits (brain)

  • Specific symptoms for alveolar echinococcosis:

    • Liver – primary site of infection

    • Progressive liver dysfunction – can lead to liver failure

    • It may take years for the hydatid cyst to progress and cause organ insufficiency

    • Distant metastasis (13% of the patients) – most common: lung, brain or bone.

Diagnosis

These are the most common methods used for the diagnosis of the hydatid cyst:

Patient (medical) history

  • Living/visiting an endemic area

  • Exposure to the parasite – ingestion of food or water contaminated by feces

Physical examination

  • Skin

    • Jaundice – biliary obstruction

    • Spider angiomas – liver cirrhosis

    • Urticaria, erythema – signs of allergic reaction to the cyst

  • Vital signs

    • Fever – can appear as the result of the secondary infection or as an allergic reaction to the cyst

    • Low blood pressure – the hypertension is common in patients who experience an anaphylactic reaction to the rupture of the cyst (leak)

  • Lungs

    • Decreased breath sounds (airway obstruction)

    • Areas of consolidation – may involve from a small part to the whole lung

  • Abdomen

    • Abdominal tenderness

    • The liver is increased in size – upon palpation, a mass can be identified in the area

    • If the patient also presents fever and/or chills, the suggested picture is of secondary infection

    • Ascites (rarely encountered)

    • Increased size of the spleen – either due to the cyst being located in the respective organ or as the result of portal hypertension

  • Extremities

    • Bone or muscle involvement – tenderness and palpable mass

    • Rare occasions – peripheral nerve compression (leading to sensory or motor deficits)

  • Brain

    • Neurological deficits (depending on the area in which the cyst is located)

    • Coma (ranging from mild to full)

    • Cerebral herniation

  • Eyes

    • Rare involvement

    • Decreased visual acuity

    • Blindness

    • Exophthalmia

Laboratory testing

  • Liver enzymes

  • Leukocytes

  • Immunoglobulins

Imaging studies

  • X-ray – non-specific findings or normal

  • Ultrasound – can be used for the diagnosis (daughter cyst present)

  • CT scan – 98% accuracy in diagnosis the daughter cysts

  • MRI – high accuracy, same as the CT scan (no superior advantage)

Other tests

  • Casoni test – intradermal skin test

  • Endoscopic retrograde cholangiopancreatography – can be used to diagnose the biliary rupture caused by a hydatid cyst (diagnostic and therapeutic investigation).

The differential diagnosis can be made with the following conditions: abdominal abscess, acute liver failure, biliary colic, biliary obstruction, liver or lung abscess, portal hypertension, primary hepatic carcinoma and tuberculosis.

Complications

The risk of morbidity appears in the following situations:

  • Rupture of the hydatid cyst (with or without anaphylaxis)

  • Cyst infection

  • Dysfunction of affected organ

The hydatid cyst can lead to the dysfunction of different organs in more than just one way. It can cause the obstruction of the biliary ducts, lead to cirrhosis of the liver or obstruct the bronchi. At the level of the kidneys, it can lead to the obstruction of the renal outflow. If it appears in the brain, it can cause an increase in the intracranial pressure; hydrocephalus can occur as a complication, due to the obstruction of the cerebrospinal fluid outflow.

There are also systemic complications that can occur, as an anaphylactic reaction to the presence of hydatid cyst in a respective organ. Among the most serious complications, there are:

  • Sepsis

  • Cirrhosis of the liver

  • Respiratory failure

  • Operative complications

  • Sudden death.

Among the secondary complications that can occur as a result of the hydatid cyst leaking, there are:

  • In case of a minor leak:

    • Pain

    • Mild allergic reaction – flushing, urticaria

  • In case of a major leak (rupture):

    • Severe anaphylactic reaction – emergency treatment is required before the symptoms become life-threatening

  • Rupture into the biliary tree

    • Obstruction by the daughter cysts – cholangitis

  • Rupture into the bronchi

    • Expectoration of cyst fluid

  • Cyst infection

    • Primary or secondary

    • The secondary infection is due to the rupture of the cyst into the biliary tree (this is known as a cystobiliary fistula)

      • Mild fever

      • Full-blown sepsis

  • Bone/muscle involvement

    • Pain at the level of the extremities

    • The neurological deficit may or may not be present.

Treatment

These are the most common treatment measures that can be taken for the hydatid cyst:

Surgical intervention

  • Recommended for the cystic echinococcosis (best outcome and definite cure)

  • New alternatives are in testing – PAIR technique (puncture, aspiration, injection, re-aspiration)

  • Radical excision – for the alveolar echinococcosis

    • May be combined with chemotherapy for a better effect

Chemotherapy

  • Used as a treatment on a long-term basis in the hydatid cysts that have been partially resected or in those that cannot be resected (aggressive treatment)

  • Indicated in patients who are diagnosed with inoperable cysts at the level of the liver or the lungs; also, in patients who present cysts in two or more organs or in those with peritoneal cysts

  • Not recommended in case of pregnancy, suppression of the bone marrow or chronic hepatic disease

Interventional procedures

  • Performed in patients with alveolar echinococcosis

  • Endoscopic, ultrasound or CT scan guidance necessary

  • May affect the functioning of the respective organ

  • Common procedures include: sclerosis of esophageal varices, collection drainage or stenting.

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