Symptoms of colorectal cancer

In addition to the early stage of colorectal cancer, which may have an insidious onset and no symptoms, advanced colorectal cancer often has clinical manifestations of varying degrees. At this time, as long as you are vigilant, ask about the medical history in detail, conduct a careful physical examination, and supplement with laboratory, endoscopic and X-ray examinations, it is not difficult to make a correct diagnosis.

1. Medical history

A detailed medical history can often reveal the diagnosis of colorectal cancer. For those who are middle-aged or older and have unexplained weight loss, anemia, changes in bowel habits, mucus in stool, blood in stool, intestinal obstruction, etc., the possibility of colorectal cancer should be considered. In order to detect colorectal cancer early, some people who have no obvious symptoms but have risk factors for colorectal cancer, such as those with a family history of colorectal cancer, those who have suffered from multiple polyposis of the colon, ulcerative colitis, Crohn's disease, chronic schistosomiasis, or those who have received pelvic radiotherapy or cholecystectomy, should be followed up and reexamined regularly.

2. Physical Examination

A comprehensive physical examination not only helps to correctly diagnose colorectal cancer, but also estimates the severity of the disease, the invasion and metastasis of cancer, and serves as a reference for formulating a reasonable treatment plan. Local signs should pay special attention to intestinal obstruction, abdominal mass, and abdominal tenderness. Since the vast majority of colorectal cancers occur in the rectum and sigmoid colon, a digital rectal examination should be essential. Whenever a patient has symptoms such as blood in the stool, changes in bowel habits, and deformed stools, a digital rectal examination should be performed. During the examination, find out whether the anus or rectum is narrowed, whether the finger cuff is stained with blood, and if a mass is touched, its location, shape, range of lesions, activity of the base, and its relationship with adjacent organs should be clarified.

Evaluation of colorectal cancer diagnosis and population screening

As mentioned above, the incidence of colorectal cancer has been increasing year by year, with a high mortality rate, and the 5-year survival rate is closely related to the Dukes stage. Since the cause of colorectal cancer is unknown, the improvement of survival rate depends on secondary prevention, that is, early diagnosis of colorectal cancer. Early diagnosis includes two meanings: one is early detection, and the other is early diagnosis. At present, due to the widespread use of fiber colonoscopy, endoscopic pathological tissue sampling and biopsy have become very simple and easy, so it is not very difficult to diagnose precancerous lesions or early cancer. However, the early detection of colorectal cancer still faces many obstacles. The main reason is that the symptoms of early colorectal cancer are often hidden, and patients who come to the doctor are often in the late stage of cancer; in addition, there is currently a lack of specific laboratory examination methods for early cancer diagnosis.

Conducting a census of asymptomatic people or monitoring patients with a family history of colorectal cancer or confirmed precancerous lesions is an important way to detect early cancer. Since the diagnosis of cancer often relies on fiber colonoscopy and pathological biopsy, any form of census must take into account workload, economic costs and social tolerance. Conducting initial screening tests to narrow the high-risk population can make up for the shortcomings of fiber colonoscopy in application. Even if we consider screening efficiency alone, initial screening tests can improve the detection effect of fiber colonoscopy. For example, in a census of more than 10,000 people, we compared the results of simple sigmoidoscopy and immune occult blood-colonoscopy sequential census and found that after the initial screening test, sigmoidoscopy can be used to detect cancer first.

As a primary screening test for colorectal cancer, the method must not only be sensitive and specific, but also simple, easy to use, economical and practical. So far, many methods have been tried for experimental diagnosis of colorectal cancer, but most of them are difficult to meet the above requirements. This is because most diagnostic indicators only have average differences between colorectal cancer patients and control patients, but they are not specific, it is difficult to establish the diagnostic threshold of cancer, and they are often insensitive to early cancer. According to the colorectal cancer survey data worldwide, the primary screening tests currently used for surveys are mainly fecal occult blood tests and rectal mucus T antigen tests developed in recent years. In addition, the use of monoclonal antibodies to detect colorectal cancer-related antigens in blood or feces is being tried in a small range of survey populations.

There are many methods for fecal occult blood tests. The chemical occult blood test method is simple, but it is easily affected by many factors and may result in false positives (such as eating meat, fresh fruits, vegetables, iron supplements, aspirin, etc.) and false negatives (such as long-term retention of feces, decomposition of hemoglobin in the intestinal cavity, and taking antioxidants such as vitamin C, etc.). Immunoassay is the second generation of colorectal cancer screening test after the chemical occult blood test. Its outstanding advantages are strong specificity and no interference from food and drugs. The early research was the agar immunodiffusion method, but we found in the application that although the specificity of this method is good, its sensitivity for cancer detection is not superior to that of the chemical method. Subsequently, we compared the reverse indirect hemagglutination test, the immunolatex test, and the SPA coagulation test. The principle is to coat human hemoglobin antibodies on a carrier. The results showed that the SPA immunooccult blood test can greatly improve the sensitivity and specificity of occult blood detection. In the 8233 cases surveyed, we found 934 positive patients, of which 4 cases of colorectal cancer were detected, and 3 were early cancers. It is worth mentioning that the SPA test uses staphylococci containing A protein as a carrier. The antibody labeling does not require purification or complicated treatment. During the operation, only a drop of fecal fluid needs to be collected on site and mixed with the SPA reagent. Stable results will appear within 1 to 3 minutes, so it is very suitable for censuses.