Anoscopy
Before performing an anoscopy, visually inspect the area, then perform a digital rectal examination (DRE) to investigate for bleeding or an obvious mass. A DRE can also help to localize pain prior to the procedure.
In some cases, it may be beneficial to clear the rectum of stool. An enema may also be administered in cases of obstipation to help clear the rectal vault prior to the procedure.
When using an anoscope with an obturator, it is important to ensure that the obturator of the anoscope is completely inserted.
Generously lubricate the anoscope with standard lubricating jelly or lidocaine jelly. Introduce the anoscope gently, and advance it slowly with a slight side-to-side twisting motion while the patient bears down. If resistance due to contraction of the external anal sphincter is significant, constant pressure on the anoscope eventually fatigues the muscles and permits insertion.
Maintain pressure over the obturator with the thumb during insertion to keep the obturator from slipping out. To avoid pinching the anal mucosa, completely remove the anoscope, and reinsert the device if the obturator slips or falls out during insertion. Some anoscope models have small tabs at the operator end of the device. These tabs should be aligned along the rostral-to-caudal axis of the patient to allow complete insertion of the device.
Once the anoscope is completely inserted, remove the obturator.
As the anoscope is slowly withdrawn, the anal mucosa can be visualized over the entire circumference of the canal. Any debris or blood can be swabbed for analysis, if desired. As the instrument is withdrawn at the anal verge, spasm of the external sphincter may lead to rapid expulsion. Firm counterpressure prevents expulsion. Reinsertion may be required for adequate visualization of the anal verge.
High-resolution anoscopy
During high-resolution anoscopy (HRA), a microscope similar to a colposcope is used to magnify the view. A 3% acetic acid solution is applied and left in contact with the perianal skin and mucosa for 2 minutes, after which Lugol iodine solution is applied. Anal intraepithelial neoplasia (AIN) lesions usually acquire a whitish colour when in contact with acetic acid and and will not take Lugol; these properties allow them to be identified and biopsied. It must be kept in mind, however, that HRA is operator-dependent and requires substantial expertise [18] ; a scarcity of appropriately trained providers can present a barrier to its implementation. [19]
An approach to HRA has been described that makes use of anal chromoendoscopy with standard gastroenterologic video-endoscopes to diagnose AIN. Oette et al found this method to be safe and effective in diagnosing AIN in a population of 211 HIV-infected patients and suggested that it was particularly useful for excluding high-grade lesions at the highest risk for progression to anal carcinoma. [20]
HRA has commonly been performed in a clinical setting, with subsequent ablation performed in the clinical setting or operating room (OR). A study by Moeckli et al found that detection rates for anal dysplasia on HRA were significantly higher when the procedure was performed in the OR, [21] suggesting that patients with high-grade dysplasia on anal pap testing might benefit from proceeding directly to the OR for concurrent HRA and ablation.
Guidelines outlining initial minimum competencies for the clinical practice of HRA were proposed by the Board of the International Anal Neoplasia Society (IANS) in 2016. [22]
Complications
Anoscopy is a relatively safe procedure. The most common complication is minor irritation of the local mucosa, which can lead to some bleeding. To avoid contamination, do not reuse multiple-use anoscopes without proper sterilization. Dispose of single-use devices after use.
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Disposable anoscope with integrated light source. Image courtesy of Welch Allyn.
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Plastic disposable anoscope with obturator in place.
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Plastic disposable anoscope with obturator removed.
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Standard lubricating jelly.
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Stainless steel anoscope. Image courtesy of Welch Allyn.
