Anoscopy - rectoscopy

Anoscopy is a simple procedure that is useful in evaluating perianal and anal complaints in a patient. The procedure may be performed in the office or the emergency room with a minimum of equipment and patient preparation.

Anoscopy provides direct, sequential visualization of both external perianal and internal anal structures. The internal anal structures may be visualized up to the lower valve of Huston. Along with visualization, the anoscope provides a working aperture for the operator to perform swabs, do biopsies, and manipulate intraanal instruments (James DM (ed), 2001) .

Two types of anoscopes

There are two basic types of anoscopes – their use depends on indications for procedure (James DM (ed), 2001) :

1. The tube-type anoscope is a cylindrical tube about 7 to 10 cm in length. It is generally made of plastic and is disposable (Fig. 1). The distal end of the anoscope is smoothly bevelled for patient comfort and has a diameter of 2.5 cm. This type of anoscope is ideal for examination of the internal anal structures, obtaining swabs or biopsies of the anal canal, or passing instruments to manipulate anorectal objects (including foreign bodies).

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   Fig. 1. Disposable anoscopes

2. The slotted anoscope is generally 7 cm in length and has a large fenestration on one side of the tube, with a smoothly bevelled distal end (Fig. 2, 3). These types of anoscope are generally made of metal and are ideal for treatment of haemorrhoids and other small lesions on the sides of the anus or anorectum.

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Fig. 2. Slotted anoscope (Hirschman type)

All anoscopes have a removable, smooth obturator that helps during insertion. After insertion, the obturator is removed and the light source is attached to the anoscope for aid in visualization.

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Fig. 3. Rectoscope (in sealed packing) with eyepiece, light cable and insufflatory bulb

Anatomy

• The terminal portion of the large intestine consists of two parts: the sigmoid colon and the rectum. Rectosigmoid junction is a sharp bend which begins approximately 15 cm proximal to the anal verge.
• The rectum, located proximal to the anal canal, contains three semicircular valves (valves of Houston or transverse folds of the rectum), and is continuous with the anus. A network of striated muscle that forms both the internal and the external anal sphincters regulates the anal outlet (Fig. 4).

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Fig. 4. Anatomy of the anal canal

• Dentate line, located approximately 2 cm proximal to the anal verge, marks the transition between columnar epithelium proximally (innervated by the autonomic nervous system) and squamous epithelium distally (innervated by the somatic nervous system) The patient can experience painful somatic sensation distal to the dentate line.

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Fig. 5. Rectal examination: Line drawing showing frontal view of intestines and rectal exam procedure

Indications for anoscopy

• Fissures or fistula in ano
• Initial evaluation of rectal bleeding
• Rectal pain
• Anal discharge or itching
• External or internal haemorrhoids (diagnostic or therapeutic, i.e. for banding or injection of haemorrhoids)
• Palpable masses or pain on digital rectal examination
• Anal condylomata

Contraindications to anoscopy

• Massive lower GI bleeding
• Anal stricture
• Acute perirectal abscess
• Acutely thrombosed haemorrhoid

Technique  (Chen H, Sonnenday CJ, Lillemoe KD (eds), 2000)

• Patient positioning: lateral decubitus (Sim’s) position or lithotomy position.
• The anus should be examined by gently spreading anoderm and performing digital rectal examination (DRE) (Fig. 6).

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Fig. 6. Digital rectal examination

• The anoscope must be inserted slowly, using liberal amounts of a water soluble lubricant, and with the obturator in place, until the flange at the base rests on perianal skin.
• The obturator should be removed and, while withdrawing the anoscope, the anal mucosa is examined in a systematic manner.
• The obturator should be replaced prior to removal of the anoscope.

Complications

• Fissure: anal or perianal tears (if occur, they usually respond to conservative measures, e.g. stool softeners and Sitz baths).
• Bleeding: rare but may occur especially if large internal haemorrhoids are present; it is usually self-limited.

Glossary

HES

Hemalun Eosine Safran (histology, French: Cell components revelation method)