Lymphoma of the Small Intestine - Causes, Symptoms, and Management

What Is Opisthorchiasis?

It is an infection caused by a parasite that belongs to a subgroup of liver flukes. Liver flukes are a group of parasites that cause liver and bile duct disease in infected humans. There are two types of liver flukes based on geographical distribution, life cycle, and long-term outcomes, they are-

• Opisthorchiidae - Includes species of Clonorchis and Opisthorchis. The species Opisthorchis is further classified into two types-

  • Opisthorchis Viverrini - Also known as South Asian liver fluke.

  • Opisthorchis Felineus - Also known as cat liver fluke.

• Fasciolidae - Includes the species Fasciola.

Opisthorchiasis is an infection caused by the species Opisthorchis. People who consume raw fish or uncooked fish, crabs, or crayfish in areas of Asia and Europe, including Thailand, Laos, Cambodia, Germany, Italy, etc., where the species is abundantly found, are susceptible to opisthorchiasis.

Most people do not show any immediate signs and symptoms of infection and only are aware of it as a result of serious illness that is caused after the completion of the lifespan (25 years to 30 years) of the parasite. Typical symptoms of opisthorchiasis include indigestion, abdominal pain, diarrhea, and constipation, although these will vary depending on the duration of the infection. In rare cases, patients have been known to develop opisthorchiasis-induced-bile duct cancer, commonly known as cholangiocarcinoma.

How Does One Become Infected With Opisthorchis?

The life cycle of liver fluke starts with the deposition of fully developed eggs by the adult liver flukes, these are passed into the environment through human feces. The eggs of these parasites get ingested by freshwater snails that become the intermediate host for the parasite.

In the snail, the parasite undergoes several developmental stages- sporocyst, rediae, and cercariae. The freshwater snails release the cercariae into the water which are then consumed by the freshwater fish which becomes the parasite's second intermediate host.

In the fish, the parasite undergoes a few more changes and becomes an encysted (enclosed in a cyst) metacercariae which hides in the muscles and under the scales of the infected fish. When humans consume these infected fish in their uncooked form, the metacercariae enter the digestive system after ingestion. Once they reach the small intestine (duodenum), they ascend through the ampulla of Vater and then into the biliary ducts where they exocyst and get attached to the wall of the duct. After three to four weeks, they develop into adults and start producing eggs thus repeating the cycle all over again.

What Are the Signs and Symptoms of Opisthorchiasis?

The infection causes a number of hepatobiliary diseases, the symptoms and the consequences of the infection depend on the intensity and the duration of the infection. The adult flukes mechanically injure the bile ducts and the metabolic products released by them irritate the biliary lining leading to an array of symptoms, they are as follows:

• Acute Opisthorchiasis - Most people infected with Opisthorchis do not experience immediate symptoms, this is because the two groups of people who are at risk of getting the infection, the locals and the travelers have acquired immunity due to repeated exposure and vaccinations respectively. However, in a few individuals, the following symptoms are seen:

  • High-grade fever.

  • Malaise.

  • Anorexia.

  • Diarrhea.

  • Constipation.

  • Dull pain and discomfort in the upper right quadrant of the abdomen.

  • Arthralgia.

  • Lymphadenopathy.

  • Urticarial skin rash.

• Chronic Opisthorchiasis - The parasite lives up to 45 years in a human host, during this time, the adult flukes mechanically injure the bile ducts and release their metabolic products into the ducts. This leads to irritation of the biliary epithelium, desquamation, hyperplasia, dysplasia, and fibrosis which cause the following complications:

1. Cholangitis - This is the inflammation seen around the biliary tree as a result of the host immune response that mediates much of the hepatobiliary damage is opisthorchiasis.

2. Biliary Fibrosis - Chronic inflammation and persistent irritation caused by the infection stimulate the deposition of fibrous tissue. The persistent irritation happens through various sources, they are:

- Mechanical irritation happens when the oral and ventral suckers of the flukes hook onto the epithelium of the biliary duct.

- Feeding and migration of the flukes.

- Metabolic products released by the tegument and the excretory opening of the flukes, these products are immunogenic, mitogenic, and toxic to the bile duct.

3. Cholangiocarcinoma - This is a life-threatening complication of chronic opisthorchiasis that occurs as a result of skewing of the immune response towards TH1, TH2, and regulatory T cells.

It is primary cancer that develops rapidly and has a very poor prognosis. There is no medical treatment available and the majority of patients die within a year of diagnosis.

How Is Opisthorchiasis Diagnosed?

In patients with acute symptoms, a detailed travel history, medical history, and stool examination will help to diagnose opisthorchiasis, however, in patients suffering from chronic opisthorchiasis, stool examination is unlikely to aid in the diagnosis.

In these patients, the cysts containing the parasites can be detected with the help of an ultrasound, a computed tomography (CT) scan, or an MRI (magnetic resonance imaging). Blood tests are not useful in diagnosis and patient management.

A recent development in detecting parasites is the loop-assisted isothermal amplification (LAMP) method. This method is simple, sensitive, and specific, but is yet to be commercially available.

How Is Opisthorchiasis Treated?

Antihelmintic drugs like Praziquantel and Albendazole are effective against opisthorchiasis. Acute complications resolve after removing the underlying infection but chronic complications often end up being life-threatening, especially in cases of cholangiocarcinoma. There is no surgical or supportive treatment for patients with non-resectable cholangiocarcinoma that has developed as a result of chronic opisthorchiasis.

How to Prevent Opisthorchiasis?

The good old saying, “Prevention is better than cure” aptly applies to patients suffering from opisthorchiasis. It can be prevented by avoiding raw and uncooked fish and by following the FDA (Food and Drug Administration) guidelines which are-

• Cook fish adequately to an internal temperature of at least 145 degrees Fahrenheit.

• Freeze the fish at an appropriate temperature and time: - 4 degrees Fahrenheit for at least 7 days or - 31 degrees Fahrenheit for at least 15 hours to 24 hours.

Conclusion

Opisthorchis is a parasite that is endemic in nature, it is present in only certain areas of the world, mainly in northeast Thailand, Laos, Cambodia, and central and south Vietnam. It has also been found in Italy, Germany, Russia, Kazakhstan, Belarus, and Ukraine. People who live in these areas are susceptible to opisthorchiasis only when they consume raw fish, drinking the river water will not infect them with Opisthorchis.

That being said opisthorchiasis has been reported in Asian immigrants, and travelers (to Asia, Russia, Germany, etc.). and in people who have consumed freshwater fish that has been imported from countries containing Opisthorchis.