Diagnosis of colon cancer performs the following main tasks:
- establishment of localization of colorectal cancer, its extent, anatomical form of growth and morphological structure;
- determination of local and long-term prevalence of the tumor process;
- Assessment of the general condition of the patient and the function of vital organs and systems.
Examination of the patient begins with a careful study of complaints, the history of the disease. In case of physical examination, attention should be paid to the color of the skin, the condition of the peripheral lymph nodes, to a greater extent inguinal. With palpation of the abdomen, a tumor-like formation can be detected, as a rule, with a large tumor size, as well as a painful infiltrate, indicating the attachment of inflammation. In depleted patients, the liver affected by metastases can be palpable.
Objective research ends with palpation of the rectum, and in women - with vaginal examination. Finger research is effective in 70% of patients. If the tumor is reached by a finger, then it is possible to determine its localization from the edge, as well as mobility with respect to surrounding structures.
Recto-manoscopy can diagnose cancer of the rectum and lower parts of the sigmoid colon, determine its extent, anatomical form of growth, and also take a biopsy to determine the morphological structure of the tumor.
X-ray examination of the colon allows one to recognize up to 90% of tumors. As a contrast agent, barium sulfate is used most often. Contrast substance can be taken through the mouth and then following its progress along the gastrointestinal tract is observed with the help of repeated X-ray studies. More often use the introduction of contrast by enemas. The technique of such an X-ray examination (irrigoscopy) consists of the following stages:
- the study of the contours of the intestine when it is filled with contrast;
- study of the mucosal relief after partial bowel evacuation;
- study after introduction into the gut of air (double contrasting).
X-ray signs of colon cancer:
- obstruction of the lumen of the gut with pronounced deformation of the contours;
- narrowing of the lumen of the intestine;
- defect filling;
- flat "niche" in the contour of the intestine;
- change in the relief of the intestinal mucosa;
- absence of peristalsis on the altered segment of the intestine;
- Stiffness of the intestinal wall;
- violation of the evacuation of contrast.
Colonoscopy is an endoscopic method of research of the large intestine. This method of diagnosis is available for tumors up to 1 cm in diameter, which are often determined by irrigoscopy. Unfortunately, it is not always possible to perform a full colonoscopy. In this regard, the entire colon should be examined both with the help of a colonoscopy and an irrigoscopy. This is of particular importance in multiple lesions of the large intestine, when the distally located tumor narrows the lumen of the intestine and does not allow the colonoscope to pass beyond the narrowing site. Thus, the above tumors are diagnosed during surgery or, worse, after it. Visual diagnostics at a colonoscopy is necessarily verified morphologically.
To evaluate the T criterion, the theoretically ideal method is endoscopic ultrasound. Ultrasonic colonoscopy is proposed as a method of refining the diagnosis of epithelial neoplasms of the large intestine, which, according to endosonographic criteria, differentiates benign and malignant tumors, determines the depth of their invasion into the intestinal wall, and determines the presence of metastases in regional lymph nodes.
With the help of ultrasound colonoscopy it is possible to obtain previously inaccessible by nature, volume and quality of diagnostic information:
- detection and evaluation based on the known endoscopic semiotics of various neoplasms of the colon, determining their nature, size, type of growth, obtaining tissue fragments for morphological study;
- determination of the absence or presence of tumor invasion (including an assessment of its depth) of the detected tumor into the thickness of the wall of the large intestine;
- determination of local prevalence of detected malignant tumors, involving in them adjacent to the affected area of the intestinal wall of organs and tissues, regional cavernous lymph nodes.
It was found that the sensitivity of ultrasound colonoscopy in the differential diagnosis of epithelial neoplasms of the colon is 96.7%, specificity 82.4%.
Correct determination of the depth of tumor invasion of the colon wall is possible in 75.4% of cases, with the best results obtained in the establishment of T3 and T4 invasion, where the diagnostic accuracy was 88.2 and 100%, respectively.
The accuracy of ultrasound colonoscopy for visualization of regional lymph nodes is 80.3%, sensitivity - 90.9%, specificity - 74.4%. In assessing the nature of visualized cecal lymph nodes by ultrasound, the diagnostic accuracy is 63.6% y
In a comparative aspect, the resolving possibility of ultrasound colonoscopy and other instrumental diagnostic methods has been studied.
According to all criteria of effectiveness evaluation, the method of ultrasound colonoscopy surpasses the routine (accuracy is higher by 9.5%, sensitivity by 8.2, specificity by 11.8%). The ultrasound colonoscopy for diagnostic efficiency is superior to the X-ray method for the study of neoplasms of the large intestine. The accuracy of ultrasound colonoscopy was higher by 6.7%, sensitivity by 20, specificity by 10%.
Thus, ultrasound colonoscopy is the most informative, non-invasive, repeatable, safe method of objective refining diagnostics of epithelial neoplasms of the colon, the diagnostic efficiency of which far exceeds that of all the routine methods of instrumental diagnostics used so far in clinical oncology.
The possibility of determining the presence of tumor germination through the intestinal wall by the method of computed tomography (CT) is very limited in comparison with EUS. Indeed, a good sensitivity of CT (82-89%) is adjacent to a low specificity (51%), mainly due to the fact that the tumor has an external edge of irregular shape surrounded by edematous periorrectal fat tissue, which causes a reassessment of stage distribution.
Nuclear magnetic resonance imaging (NMR) can not evaluate tumor infiltration of the rectum wall with high accuracy, but like CT it gives a good idea of the involvement of surrounding tissues and structures and in 81% -82% of cases predicts damage by metastases of regional lymph nodes.
Concerning the evaluation of criterion N, certain information can be obtained by EUS, CT pelvis and NMR. More specific studies, such as lymphangiography, interstitial lymphoscintigraphy (with Tc-99t of antimony trisulphide, a colloidal solution administered to a depth of 4 cm in each saddle-and-rectal fossa), rectal lymphoscintigraphy (from Tc-99t - colloidal solution of tin sulfide, introduced into the submucosa rectum using a special needle through the rectoscope) and immunolymphoscintigraphy of the rectum with monoclonal antibodies are used to improve the accuracy of diagnosis of lymph node involvement metastases.
Finally, regarding the evaluation of criterion M, it is known that synchronous liver metastases develop in 10-15% of patients with rectal cancer, manifesting pain in the right upper quadrant of the abdomen: right upper quadrant, right posterior thorax or right shoulder. Pain can be chronic or acute, caused by hemorrhage or necrosis of metastases. Liver enlargement can be diagnosed by routine clinical examination of patients who do not complain. Liver echo- tomography (ultrasound) is the first method in the diagnosis of metastases, although less accurate than CT or NMR, especially in patients with diffuse lesions of the liver parenchyma, as fibrosis and tissue scarring can mask the presence of small tumors. However, CT and NMR should not be used when there is no clear indication. Patients whose metastases in the liver are diagnosed with ultrasound should undergo preoperative transcutaneous needle biopsy in order to better plan surgical treatment.
To plan treatment and determine the prognosis of the disease, it is necessary to determine the characteristics of the biological aggressiveness of tumors with different growth rates, and, consequently, different kinetic and clinical features.
The most important here are the operative markers, such as CEA, the degree of differentiation, the indices of cell proliferation, the ploidy of DNA. The test with cancer-embryonic antigen (CEA) is useful and is the basis for monitoring the patient and helps forecasting. Indeed, there is a clear correlation between the preoperative level of CEA, the differentiation and stage of the disease. In highly differentiated tumors, CEA increased in 61% of cases, while in low-grade cases only in 3.5% of cases. In addition, CEA values correlate with the stages of the tumor process (the more neglected stage, the higher the CEA).
The degree of differentiation of tumor cells (G) is another useful preoperative parameter that can help in the biological assessment of colon tumors. Currently, four degrees of differentiation are distinguished: G1 - highly differentiated tumors; G2 - tumors of medium differentiation; G3 - low-grade tumors; G4 - undifferentiated tumors. This classification is based on the analysis of various gastopathological criteria of tumor cells, such as mitotic index, loss of nuclear polarity, nucleus size, hyperchromatism, atypia of glands and cells, pleomorphism and invasiveness. About 20% of tumors of the rectum are highly differentiated, 50% of medium differentiation, the remaining 30% are poorly differentiated and undifferentiated. It is emphasized that the degree of differentiation is clearly correlated with the presence of metastases in the lymph nodes: indeed, lymph node metastases are observed in Gl, G2 and G3-4 in 25, 50 and 80% of cases, respectively.
The histogram of flow cytometry of the colorectal cancer DNJ was performed in comparison with the tumor size, Duke staging, the degree of differentiation, the preoperative level of CEA, and the survival of the patient. In the study of diploid DNA in tumors, the prognosis was statistically worse (p = 0.017) with non-diploid DNA compared with diploid DNA, but the worst prognosis is in the presence of tetraploid DNA in tumor cells.
Screening of colonic cancer
To date, the ways and methods of early detection of cancer and precancerous diseases of the colon are being sought. The expediency of conducting preventive examinations in order to detect diseases of the large intestine is beyond doubt. However, during examinations the doctor faces a number of difficulties and, first of all, the unwillingness of a practically healthy person to undergo such procedures as rectoscopy, colonoscopy, etc. That is why it is necessary to develop an organizationally easily feasible study. This is currently the test for fecal occult blood, which was developed in the early 1960s, and since 1977 has been introduced into a wide clinical practice. This method is based on the famous guaiacol reaction, modernized by Gregor and called the "hemoculture test".
To date, the hemoccult test is the only screening test for the presence of colorectal cancer. It is simple in execution, does not require large expenses. This test is widely used in Europe and the US, as well as in South-East Asia and Japan. With the help of a hemoculture test, it is possible to reduce the death rate from colorectal cancer by 14-18%.
Screening of colorectal cancer should be carried out at least once every two years. With a positive result, each patient must perform a colonoscopy.
Since colon cancer develops primarily from polyps, which can also be detected with a hemocculant test, this method can be considered not only as a method of early detection of cancer, but also as a method of prevention. Detection and treatment of colon polyps is an important preventive measure in reducing cancer of the rectum and colon.
In the United States, another screening test is proposed for the early detection of rectal and colon cancer. The method is based on the analysis of mucus, taken from the rectum. Painted with Schiff's reagent, mucus changes its color if there is neoplasia in the colon. The method is simple, cheap, fast and does not give a large percentage of false positive and false-negative results. To the test is attached a set for its execution.
Recently, considerable interest has been caused by the development of domestic and foreign researchers, allowing the genetic screening of colorectal cancer. Colorectal cancer cells are secreted with feces, providing the potential for early detection of the disease by a non-invasive technique.
The method is based on the detection of mutant genes TP53, BAT26, K-KA5 in isolated from stool and multiplied by polymerase chain reaction (PCR) DNA from colorectal tumors. This technique is under development, but when it comes to acceptable sensitivity and specificity, as well as the cost of its prospects, it is very promising.
Recently, for the screening of colorectal cancer, a scrotal examination of tumor M2-pyruvate kinase has been proposed. This method allows detecting necrointestinal tumors in the large intestine, is characterized by high sensitivity and specificity. The results of applying this technique have not yet been described in the domestic literature.
To improve the quality of diagnostics, it is necessary to introduce screening tests into clinical practice with the subsequent application of radiological and endoscopic methods, as well as further scientific development of criteria allowing to form a high-risk group.
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