How is the Anus Examined?
The easiest and best way to examine the anus is to insert a lubricated finger into the anus and carefully feel for abnormalities. This is called a digital rectal examination (DRE) and requires no investment in expensive equipment or any special training. It is available to every patient that sees a health care provider. We feel that DRE is the most important part of every anal exam, because it is a very good way of detecting any abnormal growths or masses. After DRE, health care providers may perform anoscopy if abnormalities are felt. Anoscopy is a simple procedure that also can be performed by most health care providers. A small plastic disposable cylindrical tube known as an anoscope is placed into the anal canal and a strong light shined inside. The examiner then looks with the naked eye for any abnormalities that correspond to what was felt on DRE.
Occasionally patients will have a sigmoidoscopy, which is a test in which a flexible tube is inserted higher up into the colon beyond the anus. Sigmoidoscopy examines the lower third of the colon and rectum, whereas a colonoscopy is an exam in which a longer tube is passed through the entire large bowel to where it connects to the small intestine. Sigmoidoscopy and colonoscopy are both tests used to screen for colorectal cancer. As the physician is inspecting the rectum they can turn the scope backwards on itself to view the anus and occasionally visualize abnormalities. However, these tests are much better for evaluating the colon and rectum than they are for looking at the anus.
It has only been since the late 1980s and early 1990s that the technique known as high-resolution anoscopy (HRA) was developed to examine the anus. Physicians in England were the first to describe this technique in which a microscope is used to examine the anus after applying vinegar. The microscope, officially called a colposcope, was first developed in the 1930s in Germany to examine the cervix for cancer and precancerous lesions. The use of the colposcope became widespread in the 1960s as a way of evaluating abnormal cervical Pap smears by directly viewing the cervix with magnification so biopsies could be performed. Biopsies are small pieces of tissue that are removed, fixed, sliced, stained, and placed on glass slides in order for the pathologist to examine them and make a diagnosis. Since 1991, our group here at UCSF has pioneered and developed this technique of HRA to examine the anus and has performed HRA on over 1,000 patients who have been enrolled in various natural history studies.
How Anal Exams and HRA are Done in the UCSF Anal Dysplasia Clinic
- Patients are first asked to tell us about their general health, medical history, immune status, medications, CD4+ lymphocyte count and viral load if HIV-positive, sexual history, any history of anal warts, dysplasia, or any other anal problems. We specifically ask if they have a heart valve abnormality that is severe enough to warrant taking antibiotics when they get their teeth cleaned to prevent infections from occurring on their heart valves. It has been our recent practice to prescribe antibiotics to such patients prior to performing any biopsies.
- Next, patients are asked to describe any anal symptoms present such as itching, discomfort, irritation, pain or difficulty with bowel movements or with receptive anal intercourse (if they have anal sex), bleeding, or any other symptoms related to their anus.
- Patients undress and lie down on the examining table on their left side with their bottom at the end of the table and their feet resting in the stirrup. A Dacron swab is moistened in tap water and inserted into the anus to collect a specimen for anal cytology as described above. This must be done PRIOR to putting any lubricant into the anus because the lubricating jelly interferes with the Pap smear.
- Then a careful DRE is performed using a combination of 2% lidocaine jelly and lubricating jelly. If patients are symptomatic with tenderness or irritation or highly anxious and hyperresponsive, then 5% anorectal lidocaine cream such as L.M.X.5 or Lidosense is inserted gently and carefully into the anal canal for a few minutes prior to proceeding with DRE. It is important to put patients at ease and make the exam as comfortable as possible because patients are often embarrassed and uncomfortable being examined. Performing DRE first has several advantages: it helps to establish trust with the patient that you are not going to hurt them, topical anesthesia facilitates examination and decreases the burning effect of 3% acetic acid that is used, and most importantly, DRE allows the detection of anal masses or areas of induration or hardness (signs of cancer) in order to direct the exam to areas of concern for possible invasion.
- The lubricated and gloved finger is swept over the entire circumference of the anal canal with attention to any areas of thickening or nodularity at the level of the internal sphincter, which corresponds to the dentate line, near the location of the squamocolumnar junction. Internally the finger is feeling for masses, warty growths, ulcerations, or hard areas. Finally, the finger is swept externally in a similar fashion to palpate for any suspicious areas perianally or externally including raised, thickened, hardened, ulcerated, or tender areas.
- After DRE, the anoscope is inserted and a wooden cotton swab that is thinly wrapped with a single ply 4 x 4 cotton gauze soaked in 3% acetic acid is inserted through the anoscope and allowed to remain in the anus for 1 minute. The swab is removed. The anoscope is re-inserted and slowly withdrawn from the rectum into the anus while looking through the binoculars of the colposcope until the anal epithelium is visualized.
- Then the anoscope is manipulated in such a way as to visualize the entire circumference of the squamocolumnar junction, which is where the majority of HPV-related lesions are located. We have found that frequent re-applications of vinegar using a wooden Q-tip are helpful in making lesions appear and also in looking between the mucosal folds and hemorrhoidal cushions. Occasionally the anoscope must be re-inserted beyond the internal sphincter in order to rotate it to visualize and/or flatten out the folds. Often during longer exams, engorgement of hemorrhoids occurs in some patients, which may complicate and make exams sub-optimal. We define an adequate exam as one in which the entire circumference of the squamocolumnar junction can be visualized and inspected.
- Normal anal epithelium is shiny, glistening, translucent, and usually grayish pink; it is seen as an edge demarcating the rectal epithelium which is also acetowhite (appearing white after the application of vinegar) and more granular or grape-like in appearance reflecting the cells of the rectum. The actual junction is often scalloped in appearance and islands of metaplasia can be seen at or near the edge as “holes” in the squamous epithelium. Squamous metaplasia is normal and refers to the area of change or transition where the squamous cells cover over the rectal cells.
- The squamocolumnar junction is examined carefully for any abnormal white areas or acetowhitening, which appear as denser opaque areas. These areas appear distinct from the normal anal tissue and acetowhitening is the first indication noted that a lesion is present. Lesions are then evaluated for their surface characteristics such as papillae or the little finger-like fronds associated with warts or changes such as micropapillae, which are simply very small papillae often characteristic of LSIL. Texture or thickening is noted and whether or not there is ulceration (an area where the surface is eroded, denuded or missing leaving a hole similar to a sore on the skin).
- Lesions are next evaluated for the presence of abnormal blood vessels, which are characteristic of high-grade or precancerous lesions. Some of these vascular changes are called punctation and mosaicism and usually indicate areas of HSIL. Cancers contain very abnormal appearing blood vessels in addition to feeling thickened or hard and in some cases may be recognized by these features.
- Once a lesion is found it can be biopsied using a forceps, which means to cut out or remove a small piece of it, which is then preserved in formalin and sent to the pathologist. We tend to biopsy the most abnormal areas as a means of determining the severity of the disease present and ensuring that cancer is not present. Biopsies taken in the clinic during HRA are usually quite small, measuring about the size of a half of a grain of rice (1/8 of an inch or 1 to 3 mm). The biopsy removes the surface and underlying tissue including the basement membrane so the pathologist can determine the level of severity of the SIL and whether or not there is invasion or cancer present.
- Biopsies are easily performed and usually quite well tolerated. No anesthesia is required other than the topical numbing jelly unless the lesions are located close to the outside and then local anesthesia must be infiltrated prior to biopsy. The nervous supply to the inside of the anus is similar to the nervous supply to the internal organs; pressure and stretching are usually felt, but not cutting and pinching per se, which is in contrast to the skin in which sharpness is easily felt. Significant bleeding and infections are extremely uncommon following anal biopsy. If brisk bleeding occurs, removing the anoscope is usually all that is needed and if that is not successful, then re-insertion of the anoscope and application of Monsel’s solution (ferric subsulfate) will usually help to stop the bleeding.
- Patients may experience mild discomfort for a few hours to a few days, but often do not feel anything. There may be bleeding with bowel movements, which can last up to a week, but often does not occur.
- The anal canal in women is usually shorter, which can make assessment difficult. Obese patients and patients with very muscular buttocks can often be quite difficult to examine.
- Once the entire circumference of the squamocolumnar junction has been examined with frequent re-applications of vinegar, then the anoscope is slowly withdrawn while looking though the colposcope to evaluate the distal anal canal and mucosa close to the verge. Lesions in this more keratinized mucosa (covered with a thicker layer of skin cells) are less common and often more difficult to characterize and require anesthesia prior to biopsy.
- Following removal of the anoscope, the lubricating jelly is wiped off and then 3% acetic acid applied to the external anus, which is then examined carefully with the colposcope. External lesions can be more challenging to evaluate. Such a lesion may manifest as a more subtle superficial ulceration or denuding of the surface epithelium, and in the presence of punctation should be biopsied. External lesions can be biopsied after infiltration with lidocaine with a variety of forceps. Bleeding is stopped by application of silver nitrate sticks and pressure.