Haven't detected colon cancer after annual physical examinations? This small test may have been overlooked

Author: Hou Jiayi, Deputy Chief Technician, Shanxi Provincial Hospital of Traditional Chinese Medicine

Reviewer: Li Ning, deputy chief physician, Shanxi Provincial People's Hospital

Mr. Zhang, 50, has taken the company's physical examination every year, and he didn't have any major problems. However, this year when he went to the doctor, he was told that he had colon cancer! He was puzzled and doubted the accuracy of the physical examination results, "Are these physical examination items useful?" After reading his physical examination report, the doctor found that there was a test that Mr. Zhang had ignored before, which led to the failure to detect colon cancer in time. This test was the fecal occult blood test.

1. What is a fecal occult blood test?

Fecal occult blood test means that when the amount of gastrointestinal bleeding is small, the red blood cells have been digested and decomposed, resulting in no obvious blood in the stool and no red blood cells can be observed under a microscope. However, after the red blood cells are destroyed, hemoglobin is released, which can be detected by chemical methods (o-tolidine method) and immunological methods (colloidal gold labeled immunosandwich method).

Figure 1 Fecal sampler

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Why do we need to do a fecal occult blood test?

The entire digestive tract, such as the mouth, esophagus, stomach, small intestine, large intestine and anus, lesions (inflammation, ulcers, tumors) in these parts can lead to positive fecal occult blood tests. The surface of colorectal cancer tumors is rich in blood vessels, which are easy to bleed when rubbed with stool. Therefore, the positive detection rate of fecal occult blood tests is relatively high. Fecal occult blood tests are convenient, non-invasive, and low-cost. They can be used as the preferred examination indicator for colorectal cancer screening, especially for early cancer screening in middle-aged and elderly people.

Mr. Zhang's annual physical examination includes this item, but he couldn't defecate that day, and he thought his stool looked normal, so he gave up this "small check". As a result, he didn't do the fecal occult blood test in his physical examination for the past two or three years, missing the opportunity to early-warning colon cancer.

Figure 2 Positive fecal occult blood test

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3. What symptoms require prompt fecal occult blood test?

The current guidelines for colorectal cancer prevention and treatment recommend that the general population should undergo an immunological fecal occult blood test during their annual routine physical examination, and if the result is abnormal, a colonoscopy should be performed, so that colorectal adenoma or colorectal cancer can be detected early. However, once the following symptoms appear, such as changes in bowel habits (constipation, diarrhea, etc.), changes in stool shape (thinner stools), changes in stool properties (blood in the stool, black stools, mucous stools, etc.), and pain in a fixed part of the abdomen, you should seek medical attention in a timely manner. For people with a family history of colorectal cancer, since the risk of colorectal cancer is significantly increased, only a fecal occult blood test can no longer meet the screening needs, and they should follow the doctor's advice to undergo regular colonoscopy examinations.

Mr. Zhang mentioned above has had mushy stools and sometimes black stools in recent months. He went to the hospital for a series of tests and found that the fecal occult blood test was strongly positive. The doctor immediately recommended that he undergo a colonoscopy, and the results showed that he was already in the middle and late stages of colon cancer. The doctor said that colon cancer progresses slowly. If Mr. Zhang had been able to detect abnormalities through fecal occult blood tests during his physical examination a few years ago and received timely treatment, his prognosis would have been better. Now, Mr. Zhang is really regretful.

It is worth noting that Mr. Zhang is not an isolated case. In routine physical examinations in my country, many people think that collecting stool is too troublesome, so they give up doing fecal occult blood tests. It is recommended that if you cannot collect stool specimens during physical examinations, you can keep them at home and take a small amount in a clean and dry container to the physical examination institution as soon as possible. I hope everyone will establish awareness of tumor screening and let this "small examination" play its due role.