Patients may present in the outpatient or emergency department setting with various anorectal conditions. A high degree of professionalism is especially warranted in these cases because of the nature of the examination.
As part of the initial evaluation, obtain a complete history of the present illness, perform a physical examination of the abdomen, and perform a visual inspection of the anus and perineum. The next step, if necessary, is a digital rectal examination (DRE).
If the data obtained from the external visualization and DRE are insufficient to make a definitive diagnosis, anoscopy may be performed to visualize the anus, anal canal, and internal sphincter.[2, 3, 4]
Indications for anoscopy include the following:
To visually investigate anorectal conditions for which a DRE does not provide sufficient diagnostic information
- To obtain information on conditions such as internal hemorrhoids or disruption and other pathology of the rectal mucosa, or to examine for an anorectal mass or foreign body in the anal canal
- To obtain samples for cytology as a screening method for anal squamous lesions, [5, 6, 7, 8] particularly in high-risk patients with HIV infection [9, 10, 11]
Anoscopy should not be performed on an imperforate anus. Caution should be exercised on patients who have recently undergone anal or rectal surgery.
High-resolution anoscopy is a preferred screening method in the diagnosis of anal intraepithelial neoplasia (AIN) ; however, despite its sensitivity in identifying patients with AIN, its routine use is not justified, and conventional anoscopy is carried out for the diagnosis of other conditions.
The anal canal is the most terminal part of the lower gastrointestinal (GI) tract (ie, the large intestine or colon). It lies between the anal verge (anal orifice or anus) in the perineum below and the rectum above. The pigmented, keratinized perianal skin of the buttocks (around the anal verge) has skin appendages (eg, hair, sweat glands, and sebaceous glands); it may be contrasted with the anal canal skin above the anal verge, which is also pigmented and keratinized but does not have skin appendages.
For more information about the relevant anatomy, see Anal Canal Anatomy.
Equipment and materials used in anoscopy include the following:
Lubricating jelly or lidocaine jelly (see the first image below)
- Sterile or nonsterile gloves
- Paper towels or tissue paper
- Disposable sheet
- Light source (if not already built into the anoscope)
- Anoscope (see the second, third, fourth, and fifth images below)
Most patients do not require analgesia for anoscopy.
Topical anesthesia is administered, with 2% lidocaine jelly inserted into the anal canal at least 10 minutes before insertion of the anoscope. If necessary, intravenous (IV) medications such as opiates (eg, morphine sulfate) or benzodiazepines (eg, lorazepam, diazepam, midazolam) may be administered for analgesia and light sedation.
In some situations, it may be reasonable to consider IV procedural sedation via local protocol with agents such as fentanyl, midazolam, propofol, ketamine, or etomidate. Such situations include the following:
The patient could not tolerate anoscopy despite topical medication and administration of initial IV medications
- Initial attempts at foreign-body removal with medication as described above were not successful, and further attempts are indicated in the current venue
For complicated cases in which the anatomy is distorted, the patient cannot tolerate the procedure, or the attempt at foreign-body removal was unsuccessful, referral to a specialist for an examination under anesthesia or admission to the hospital is indicated.
The patient can be placed in various positions to facilitate insertion of the anoscope. The most common position is the lateral decubitus position with the contralateral (top) leg flexed at the knee and the hip. The patient may also be placed in the knee-shoulder position or the prone position.
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.
During high-resolution anoscopy, 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 high-resolution anoscopy is operator-dependent and requires substantial expertise.
An approach to high-resolution anoscopy 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 exluding high-grade lesions at the highest risk for progression to anal carcinoma.
Guidelines outlining initial minimum competencies for the clinical practice of high-resolution anoscopy were proposed by the Board of the International Anal Neoplasia Society (IANS) in 2016.
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.
The goals of pharmacotherapy are to reduce morbidity and prevent complications.
Local anesthetics are used to facilitate the procedure.
Lidocaine topical (Topicaine, Lidocin, Glydo)
Decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.
Induction of anesthesia is accomplished by using opioids. Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties that are beneficial for patients who experience pain.
Morphine (Duramorph, Infumorph)
Morphine sulfate is the DOC for analgesia owing to its reliable and predictable effects, safety profile, and ease of reversibility with naloxone.
Indicated for patients that may experience significant anxiety before a surgery.
Lorazepam is a sedative-hypnotic of the benzodiazepine class that has a rapid onset of effect and a relatively long half-life. By increasing the action of gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter, it may depress all levels of the central nervous system (CNS), including the limbic system and reticular formations. Lorazepam is excellent for patients who need to be sedated for longer than 24 hours.
Midazolam is a sedative-hypnotic of the benzodiazepine class that provides initial sedation as well as amnesia.
Diazepam (Diastat, Diastat AcuDial, Valium)
Diazepam modulates the postsynaptic effects of gamma-aminobutric acid–A (GABA-A) transmission, resulting in an increase in presynaptic inhibition. It appears to act on part of the limbic system, the thalamus, and hypothalamus, to induce a calming effect. It also has been found to be an effective adjunct for the relief of skeletal muscle spasm caused by upper motor neuron disorders.
Diazepam rapidly distributes to other body fat stores. Twenty minutes after initial IV infusion, the serum concentration drops to 20% of maximum plasma concentration (Cmax).
Individualize dosage and increase cautiously to avoid adverse effects
These agents stabilize the neuronal membrane so the neuron is less permeable to ions. This prevents the initiation and transmission of nerve impulses, thereby producing the local anesthetic effects.
Fentanyl citrate is a synthetic opioid that has 75-200 times more potency and a much shorter half-life than morphine sulfate. It has fewer hypotensive effects than morphine and is safer in patients with hyperactive airway disease because of minimal or no associated histamine release. By itself, fentanyl citrate causes little cardiovascular compromise, although the addition of benzodiazepines or other sedatives may result in decreased cardiac output and blood pressure.
Fentanyl citrate is highly lipophilic and protein-bound. Prolonged exposure to it leads to accumulation of the drug in fat and delays the weaning process. Consider continuous infusion because of the medication’s short half-life.
The parenteral form is the drug of choice for conscious-sedation analgesia. Fentanyl citrate is ideal for analgesic action of short duration during anesthesia and the immediate postoperative period. It is an excellent choice for pain management and sedation with short duration (30-60min) and is easy to titrate. The drug’s effects are easily and quickly reversed by naloxone.
Propofol is a phenolic compound unrelated to other types of anticonvulsants. It has general anesthetic properties when administered intravenously. Propofol IV produces rapid hypnosis, usually within 40 seconds. The effects are reversed within 30 minutes, following the discontinuation of infusion. Propofol has also been shown to have anticonvulsant properties.
Ketamine acts on the cortex and limbic system, decreasing muscle spasms.
Amidate is a nonbarbiturate imidazole compound with sedative properties. It is short-acting and has a rapid onset of action; the duration of action is dose dependent (15-30 minutes). Its most useful feature as an induction agent is that it produces deep sedation while causing minimal cardiovascular effects.
The major application of amidate is induction for endotracheal intubation, particularly in patients with, or at risk for, hemodynamic compromise. Amidate has been shown to depress adrenal cortical function; however, this effect is not significant clinically during short-term administration. Since the drug is mixed in propylene glycol, continuous infusion not recommended.