Generality
Virtual colonoscopy is a relatively young diagnostic technique, which is a valid alternative to the traditional colonoscopic examination.
Advantages
Established in 1994, virtual colonoscopy allows non-invasive internal colon walls to be studied, saving the patient the trouble and embarrassment associated with the traditional procedure; it is also not necessary to use sedatives and painkillers, the duration of the exam is lower and immediate discharge, with the possibility of driving and resuming normal daily activities as soon as possible.
Small annoyances
However, even for virtual colonoscopy the need for adequate dietary preparation remains, with the help of specific laxatives. Furthermore, before the examination, carbon dioxide must be blown into the patient's rectum by means of a small rectal probe, after Buscopan has been administered to reduce the sense of discomfort (except for contraindications to the use of the medicinal product). All this in order to relax the walls of the colon and allow an easier study of the same; this need can produce a modest sensation of abdominal distension due to the air blown, but overall the virtual colonoscopy remains an almost painless examination, especially when compared to the classic method.
When it is performed
In addition to being a first-level method for the screening of colorectal carcinoma, in subjects over the age of 50, virtual colonoscopy is also indicated as a second-level investigation in the evaluation of individuals that are positive for the presence of occult blood in the faeces.
Colorectal cancer
It represents the second cause of mortality due to cancer both in males, after that of lung, and in women, after that of breast.
The good news is that this type of neoplasm is characterized by a slow evolution starting from polyps or adenomas, which can be exported before they turn into a malignant tumor form. If you are over 50 or if your family has had other cases of colorectal cancer, contact your doctor for more information on screening tests, a real bulwark against the development of colorectal cancer.
In patients who refuse to undergo traditional colonoscopy, the virtual method can be performed in the presence of symptoms such as abdominal pain, rectal bleeding, constipation or chronic diarrhea, frequent alterations of the alvus (periods of constipation alternating with diarrheal episodes), iron deficiency anemia unknown origin, tenesmus (feeling of incomplete stool evacuation), emission of ribbon-like excrement and abundant presence of mucus in the stool. Many of these symptoms are also attributable to the cancerous forms of colorectal cancer.
How does it work
The virtual colonoscopy exploits a technique called multilayer spiral CT and a software, constantly updated, capable of reconstructing colic walls on the screen. All this is made possible by the use of ionizing radiation, which is passed through the patient's body; at the opposite end a suitable receiver is able to record these radiations, which come out of the patient with different degrees of attenuation based on the tissues crossed (the denser they are and the greater the attenuation). By converting this data into an electrical signal, it is possible to reconstruct, with the help of a special program, the anatomy of the irradiated tissues and organs. The radiologist will then be able to observe the inside of the colon "virtually", as if he were performing a conventional colonoscopy. Theoretically, there is also the possibility of examining also the other abdominal organs, identifying possible extracolic pathological alterations.
The scan has a duration of a few seconds and the amount of ionizing radiation administered is minimal and considerably lower than a CT scan of the standard abdomen.
Advantages
Since its introduction, the sensitivity and specificity of virtual colonoscopy have gradually improved. If it is indeed important to guarantee the non-invasiveness of the procedure and minimize the discomfort for the patient, it is equally important to ensure that this technique is actually able to recognize suspected lesions against the colon. This characteristic has always been proportional to the dimensions of the same, making it excellent for formations with a diameter greater than one centimeter and scarce for those with a radius of less than 3 mm (which have a probability of becoming extremely low in malignant tumors); not surprisingly, the continuous improvements to which virtual colonoscopy is subjected are aimed precisely at ensuring the correct recognition of smaller lesions.
Thanks to this constant improvement work, it is likely that in the next few years virtual colonoscopy will replace the traditional method and the rectosigmoidoscopy as an elective screening test for colorectal cancer.
The rectosigmoidoscopy, in addition to maintaining a certain invasiveness, is not able to identify any adenomatous polyps or tumors located in the proximal and central sections of the large intestine. For its part, colonoscopy is burdened with a higher rate of complications and poor tolerance on the part of patients.
Another advantage of the virtual colonoscopy compared to the traditional one is the ability to completely visualize the whole colon, which due to the particular conformation or the presence of stenoses and diverticula may not make the examination of some traits possible (such as the blind-ascending ) with the normal optical colonoscopy. The virtual methodology therefore finds a further indication in all those cases of traditional incomplete colonoscopy, or non-executable due to the refusal of the patient or the presence of contraindications to its performance (for example in cardiopaths and chronic bronchitics).
Contraindications and Disadvantages
Due to the need to blow air into the colon, the virtual colonoscopy remains contraindicated, like the traditional one, in the presence of acute diverticulitis, toxic megacolon and recent subjection to surgery in this section of intestine.
The main limitation or disadvantage of virtual colonoscopy over the traditional remains the impossibility to intervene during the examination itself to perform small biopsy samples or to remove an abnormal polyp. Unfortunately, inevitably, in situations where the colonoscopy identifies anomalies (indicatively one case in 10), these operations become indispensable and the patient will therefore have to submit himself to the traditional examination in spite of himself.
Although the X-ray dose administered to the patient is very low and far below the maximum limits established by the authorities in force, colonoscopy should not be performed during pregnancy. Finally, there is a low ability to identify flat lesions.
Preparation
If at the time of the examination the colic walls are not thoroughly cleaned, the virtual colonoscopy can exchange simple faecal residues for anomalous masses. To prevent this possibility, the digestive endoscopy center provides the patient with a series of recommendations to follow during the approach to the exam. The preparation is often similar to that used for traditional optical colonoscopy, although it is generally less restrictive.
