"Even If It's Delicious, Never Eat 'This'..." A Doctor Says He'd Like to Put Up a Sign in His Exam Room. Why?

Liver Flukes in Freshwater Sashimi Can Cause Chronic Inflammation in the Bile Ducts
Thorough Cooking Is Key... Seek Medical Care for Abdominal Pain or Jaundice

Freshwater sashimi, a popular dish prized for its chewy texture and mild flavor, can pose a serious health risk. Clonorchis, a parasitic fluke found in freshwater fish, can settle in the bile ducts after entering the body and cause long-term inflammation and tissue damage. If the infection persists, it may also increase the risk of bile duct cancer. Experts stress the importance of cooking freshwater fish thoroughly.

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Hwang Junseong, a professor of gastroenterology at Changwon Hanmaeum Hospital, recently warned on the hospital's YouTube channel that parasites found in freshwater fish can cause gallstones and bile duct cancer. He emphasized the risk of raw grass carp sashimi in particular, saying, "I would like to put up a sign saying 'NO grass carp sashimi' in front of my clinic."

Clonorchis Infection Can Progress Without Symptoms

The main parasite to watch out for when eating freshwater sashimi is Clonorchis. Also known as the Chinese liver fluke, it can be transmitted through freshwater fish in the carp family, such as carp, crucian carp, and topmouth gudgeon. If people eat raw freshwater fish containing infective larvae, the parasites can enter the body through the mouth, pass through the small intestine, and move into the bile ducts, where they can mature into adult flukes.

One especially concerning aspect of Clonorchis infection is that it can be difficult to detect in its early stages. Many infected people experience no noticeable symptoms, but as the infection progresses, they may develop indigestion, abdominal pain, and loss of appetite. Depending on the severity, symptoms such as jaundice may also occur.

The problem is that the parasites can survive for a long time after settling in the bile ducts. The bile ducts carry bile produced by the liver to the duodenum, transporting the bile needed to digest fat. When Clonorchis remains there, it can repeatedly irritate the bile duct walls, causing inflammation and scarring and leading to cumulative tissue damage.

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These changes can obstruct the flow of bile and lead to complications such as cholangitis or gallstones. Long-term inflammation and damage are also associated with an increased risk of bile duct cancer. The International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO), classifies Clonorchis as a Group 1 carcinogen, meaning it is known to cause cancer in humans.

However, not everyone infected with Clonorchis will develop bile duct cancer. Various factors may affect the outcome, including whether a person is infected, how long the infection lasts, and the extent of bile duct damage. Professor Hwang said that evidence of a past Clonorchis infection should also be considered a risk factor for bile duct cancer.

Cook Freshwater Fish Thoroughly...Salting and Smoking Do Not Make It Safe

The surest way to prevent Clonorchis infection is to cook freshwater fish thoroughly before eating it. It is not enough to cook only the surface; the fish must be heated thoroughly all the way through. People should also be cautious about preparation methods when it is unclear whether the fish has been fully cooked, as well as avoiding raw freshwater sashimi.

In particular, fish should not be assumed to be safe simply because it has been salted, smoked, or pickled. The U.S. Centers for Disease Control and Prevention (CDC) advises that methods such as salting or smoking freshwater fish may not eliminate infectious parasites. Eating uncooked freshwater fish that has been processed in these ways does not completely eliminate the risk of infection.

Proper hygiene during food preparation is also important. Using the same knife and cutting board that were used to prepare freshwater fish on other ingredients can lead to cross-contamination, so it is best to use separate utensils. The Korea Disease Control and Prevention Agency also advises against using knives and cutting boards used to prepare freshwater fish on other ingredients without first cleaning them. Utensils should be heated in boiling water or washed appropriately, and hands should be washed thoroughly after handling the fish.

It is also important not to rely on the presence or absence of symptoms to determine whether someone is infected. Clonorchiasis can be diagnosed through tests such as examining stool for parasite eggs. If an infection is confirmed, it is treated with the antiparasitic drug praziquantel. However, if a long-lasting infection has damaged the bile ducts, the damage may not fully heal even after the parasites are eliminated, making early diagnosis and treatment important.

Do Not Let Your Guard Down Even If the Pain Subsides

Gallstones are another concern, alongside Clonorchis infection. If a gallstone blocks a bile duct, bile cannot flow properly, which can cause sudden, severe pain in the upper middle or right side of the abdomen. The pain may last for several hours and then subside when the blockage clears.

Pain that is severe but goes away within a relatively short time can easily be mistaken for ordinary stomach cramps or indigestion. However, the fact that the pain has subsided does not mean the underlying cause has been resolved. Gallstone-related pain can recur, and if the bile duct remains blocked, it can lead to more serious complications, including inflammation.

Professor Hwang said that some patients with gallstones visit the emergency room several times with symptoms resembling stomach cramps before the cause is finally identified. He described a pattern in which severe pain disappears as if by magic after three or four hours. Recurrent abdominal pain should not be dismissed as a simple digestive symptom; its cause needs to be identified.

Particular caution is warranted if severe abdominal pain is accompanied by fever, chills, or jaundice. These symptoms may indicate a condition, such as bile duct obstruction or infection, that requires prompt treatment. Anyone experiencing them should seek medical care immediately.

This content was produced with the assistance of AI translation services.