He has been receiving radiotherapy for colorectal cancer at the Hanoi Oncology Hospital since February.

His family recently gave him some dog meat, believing it was a protein-rich food "that could help improve his nutrition."

One day after eating it, he started bleeding non-stop from his eyes and had dark-red blood in his stool.

His family took him to a local hospital where he stayed for three days before being transferred to the Hanoi Oncology Hospital with severe blood loss and coagulation disorders, the hospital announced the case on Aug. 12 without revealing further when it happened specifically.

Based on his medical history and symptoms, doctors suspected that the dog meat he ate may have been contaminated with rat poison.

They then discovered he had been poisoned by a vitamin K antagonist rodenticide, which inhibits blood clotting and can cause prolonged bleeding.

"The important task is not only to stop the bleeding but identify the underlying cause," Dr Le Thi Tuyen of the hospital's intensive care unit, said.

"If the patient is given only blood transfusions or conventional hemostatic drugs, he may continue to bleed, eventually putting his life at risk."

A colorectal cancer patient is hospitalized with bleeding in the eyes. Photo by Vu Huong

The patient was then treated with high-dose vitamin K, red blood cell transfusions, fresh frozen plasma, and other blood products to replace the blood he had lost and restore his ability to clot.

After five days, the bleeding was controlled, his coagulation indicators improved, and his condition stabilized.

Doctors said the case highlights the risks posed by foods of unknown origin, particularly for cancer patients whose health and ability to withstand complications are already compromised.

They also recommended against consuming foods believed to have health benefits without consulting medical professionals.

Anyone who develops unusual bleeding like under the skin or in the eye or stools, or have abnormal symptoms after eating something should immediately seek medical attention, they added.