Colorectal cancer diagnosis involves screening tests such as colonoscopy, stool tests, and imaging studies to detect and confirm the presence of cancerous growths in the colon and rectum.
The misdiagnosis rate of colorectal cancer is relatively high in elderly individuals, mainly due to mild early symptoms that do not attract the patient’s attention. Elderly individuals often have a delayed response to symptoms, leading to a delay in seeking medical attention. Clinical physicians also often have insufficient knowledge about the symptoms of colorectal cancer and subjectively attribute them to disorders of intestinal function, hemorrhoids, chronic diseases, or colitis, without further investigation. Reports have shown that the misdiagnosis rate of rectal cancer can be as high as 50% to 80%, with many cases remaining misdiagnosed or mistreated for several years or even longer, causing patients to miss the opportunity for early cure.
(1) Symptoms requiring necessary physical examination and special tests (Colorectal cancer diagnosis):
For individuals aged 35 and above, the following symptoms should be considered as possible indications of colorectal cancer, requiring necessary physical examination and special tests:
- Recent onset of persistent abdominal discomfort, dull pain, or bloating that remains unresponsive to general treatment.
- Unexplained changes in bowel habits, such as persistent diarrhea or constipation, or alternating between the two.
- No history of dysentery, colitis, hemorrhoids, or other related conditions, but experiencing increased frequency of bowel movements accompanied by pus, blood, mucus, or bloody stools.
- Gradually worsening symptoms of intestinal obstruction.
- Unexplained anemia, weight loss, or unexplained decrease in body weight.
- Abdominal mass, particularly in the lower left or right abdomen.
- Continuous occurrence of black or tarry stools, with positive results in fecal occult blood tests.
(2) Physical examinations that should be performed for diagnosis (Colorectal cancer diagnosis):
- Abdominal inspection and palpation: Examination of the abdomen for signs of bloating, masses, tenderness, and symptoms of intestinal obstruction.
- Digital rectal examination: The physician inserts a gloved finger into the rectum for examination, which is the most important and indispensable method of examination. If the rectal cancer is located 8-10 cm above the anal margin, it can often be felt during the digital rectal examination. This examination can provide clarity on its location, size, mobility, presence of narrowing in the intestinal lumen, invasion of adjacent organs, and presence of pus or blood on the glove.
(3) Special examinations that should be performed for diagnosis (Colorectal cancer diagnosis):
- Rectosigmoidoscopy or colonoscopy: Approximately 70% to 75% of colorectal cancers are located within 25cm from the anal verge and can be detected using rectosigmoidoscopy or colonoscopy. Biopsy samples should be taken for pathological examination to confirm the diagnosis and prevent misdiagnosis.
- Barium enema or double-contrast barium enema X-ray: This is an important examination method for detecting tumors in the middle and upper segments of the sigmoid colon. The positivity rate of this examination can reach 90%. Its purpose is to observe the entire colon, check for multiple polyps and multiple cancers, and observe for local intestinal mucosal damage, filling defects, intestinal wall stiffness, and intestinal lumen narrowing. Patients with intestinal obstruction should not undergo barium enema examination, and barium meal examination is even less suitable.
- Flexible sigmoidoscopy or colonoscopy: This examination allows for a detailed observation of the internal lesions throughout the entire colon. It can be used for live tissue examination, imaging, and removal of pedunculated polyps. During surgery, when multiple lesions in the colon cannot be accurately palpated and located, a flexible sigmoidoscopy can be inserted through the anus to assist the surgeon in examination, which is highly effective.
- Carcinoembryonic antigen (CEA) testing: CEA testing is not specific for diagnosing colorectal cancer (meaning a positive CEA test does not necessarily indicate colorectal cancer), but it is important for assessing treatment efficacy, recurrence, and particularly liver metastasis. If CEA is positive and the value is high before surgery, it should return to normal within 2-3 weeks after complete tumor resection. If CEA returns to normal after surgery and then continues to rise after a period of time, it indicates the possibility of recurrence or distant metastasis. Positive CEA reactions often occur earlier than clinical symptoms.
- CT (computerized tomography) or MRI (magnetic resonance imaging) scan: These examinations are useful for observing the size and extent of postoperative recurrence or metastatic lesions, and provide important reference for determining suitability for surgical treatment.
- Fecal occult blood test: There are immunological and chemical methods for this test, with the immunological method having higher sensitivity and specificity than the chemical method. This test is commonly used for initial screening of colorectal cancer, and individuals with positive occult blood results should undergo further endoscopic examination.
When diagnosing colorectal cancer, it is important to differentiate it from the following diseases, including other malignant tumors, benign tumors, inflammation, hemorrhoids, tuberculosis, schistosomiasis, amoebiasis, sexually transmitted granuloma, trauma, chemical injury, and radiation enteritis. Diagnosis should be approached with caution and attention to detail.
