Anal and perianal disorders

From SurgWiki

Jump to: navigation, search


Anal fissure


An anal fissure is a linear tear or superficial ulcer of the anal canal, extending from just below the dentate line to the anal margin (Anatomy of the rectum and anal canal.). It usually occurs in the midline posteriorly, or sometimes anteriorly in females, particularly after a pregnancy.

Anatomy of the rectum and anal canal.


Although the precise aetiology is unknown, it is usually related to constipation and trauma to the anal canal from a hard stool. Hypertonia of the internal anal sphincter with an associated raised anal resting pressure is common.


The cardinal symptoms are severe anal pain during and immediately after defecation and anal outlet bleeding. The pain is so intense that the patient is afraid of and consequently avoids opening the bowels. The pain has been attributed to spasm of the internal sphincter.


The diagnosis is readily made on inspection. Anal fissure may be acute or chronic. Chronic anal fissure is associated with a sentinel skin tag at the anal margin and a hypertrophied anal papilla at the upper end of the anal canal. If the diagnosis is suspected on history and visual inspection of the anus, then it is important not to proceed to digital examination of the rectum: this would cause severe and unnecessary pain.

Inspection is the most important step in the diagnosis of anal fissure. This is performed with the patient in the left lateral position with the buttocks protruding well beyond the edge of the examining table. Good light must be made available. The buttocks are gently stretched apart and, providing the examiner is looking, a fleeting glimpse of the fissure will be obtained before sphincter contraction causes it to be withdrawn from view.

Differential diagnosis

Differential diagnosis includes fissures due to Crohn's disease and neoplastic ulcers. Fissures due to Crohn's disease are usually not in the midline. These fissures are deep, with indolent edges, tend to be multiple and occur at atypical sites; they are relatively painfree. Anorectal strictures or ulcers and Crohn's proctitis are usually present. Neoplastic ulcers are usually due to squamous cell carcinoma. The ulcer is deep and has heaped-up edges. Other conditions that may have to be considered include sexually transmitted diseases (syphilis and HIV).


The principal aim is to relax the internal sphincter, thereby relieving pain (which is due to spasm of that sphincter).

Conservative treatment

Conservative treatment includes the application of topical anaesthetic and hydrocortisone ointment, and a high-fibre diet to increase stool bulk (so that the stool itself dilates the sphincter). The complete healing rate is about 50% after 4 weeks of treatment. Recurrence rate is high, at about 25%. Glycerine trinitrate paste (0.2%) is effective in up to 50% of patients by relaxing the internal sphincter; however, the recurrence rate is high. It may also cause severe headache. More recent examples of chemical sphincterotomy include the use of calcium channel blockers and botulinum toxin.

Surgical treatment

Lateral internal anal sphincterotomy is the procedure of choice for chronic anal fissure or an acute fissure that remains severely symptomatic after a prolonged course of non-operative measures. The aim of surgery is to break the vicious cycle of internal sphincter spasm. The distal internal sphincter, up to but not above the dentate line, is divided under anaesthesia (Lateral sphincterotomy for chronic anal fissure.). This procedure offers almost immediate relief of pain. The large sentinel skin tag and hypertrophied anal papilla are excised. After sphincterotomy, the patient should be put on a high-fibre diet. The recurrence rate is less than 3%. Some minor impairment of control of flatus occurs in up to 10% of patients but major faecal soiling is rare. In this regard, sphincterotomy performed through the base of the fissure is best avoided.

Lateral sphincterotomy for chronic anal fissure.

Some surgeons have advocated anal dilatation using six or eight fingers instead of sphincterotomy. This technique is imprecise and associated with a high prevalence of incontinence of both faeces and gas. It has no place in the modern management of anal fissure.

Perianal abscess


Perianal abscess is a common condition that is usually due to a blocked anal gland (Spread of infection (A) from the primary anal gland abscess and (B) to the perianal region.) that subsequently becomes infected (cryptoglandular origin). There are usually no predisposing factors, but patients with diabetes, Crohn's disease or those who are immunocompromised are susceptible. The abscess may discharge spontaneously to the skin, and if a communication to the skin is established then a fistula may result. This may occur in up to 50% of patients.

Spread of infection (A) from the primary anal gland abscess and (B) to the perianal region.


Although most abscesses are perianal, sepsis can occur either above or below the levator muscle, in the intersphincteric space, submucosally or in the ischiorectal space (Types of perianal abscess: (A) ischiorectal, (B) perianal, (C) intersphincteric, and (D) submucosal.). Abscesses that involve the upper portion of the anal sphincters are complex and require specialist management.

Types of perianal abscess: (A) ischiorectal, (B) perianal, (C) intersphincteric, and (D) submucosal.


The diagnosis is readily made from a history of throbbing pain and visual inspection, which demonstrates localised swelling, tenderness and redness. A large or a deep-seated abscess, such as an ischiorectal abscess, often presents with systemic symptoms of sepsis and fever.


A full blood count and blood glucose level measurement should be performed. Further investigations should be performed if associated conditions are suspected as defined under ‘Aetiology’ above.


The most common practice is to incise and drain the abscess under local anaesthesia. Antibiotics are used if the sepsis is extensive or if the patient is immunocompromised. There is little role for antibiotics in the primary management of perianal abscess of cryptoglandular origin. It is usual to leave a small drain or packing gauze in the abscess cavity for a few days postoperatively. Bigger and deeper abscesses, such as an ischiorectal abscess, are drained under general anaesthesia. Perianal abscesses must be drained with optimal preservation of underlying anal sphincters. A sigmoidoscopy to examine the rectal mucosa should be performed in this situation. It is important to recognise these complex or horseshoe ischiorectal abscesses so as not to damage the anal sphincter. Simple drainage will suffice, followed in a few weeks by a more sophisticated test such as an endorectal ultrasound, and a further examination under anaesthesia if discharge persists. Underlying bowel disease such as Crohn's disease must be excluded in these complex situations. Almost 50% of abscesses are associated with a fistula-in-ano and therefore many of these abscesses recur. Should this happen, an examination under anaesthesia should be performed after the abscess has been drained to determine whether a fistula is indeed present.



A fistula is an abnormal communication between two epithelial-lined surfaces. Afistula-in-ano implies a communication between the anorectum and the perineal skin.


The causes of fistula-in-ano are given in Aetiology of fistula-in-ano.


The most important determinant of a fistula-in-ano is whether its internal opening is below or above the anorectal ring (Types of perianal fistulas: (A) intersphincteric, (B) trans-sphincteric, (C) supra-sphincteric, and (D) extra-sphincteric.). Those below are low fistulas and those with an internal opening above the levator are high fistulas. In general terms, low fistulas tend to be either idiopathic or associated with anal gland infection, and high fistulas have other, more serious aetiological associations.

Types of perianal fistulas: (A) intersphincteric, (B) trans-sphincteric, (C) supra-sphincteric, and (D) extra-sphincteric.

The line of communication between the internal and external openings is not always direct, and may indeed be very tortuous. Goodsall observed that when the external opening was anterior to the anus, it communicated directly with the internal opening; while when the external opening was posterior to the anus, the internal opening tended to occur in the midline posteriorly. This may produce complex fistulas with a horseshoe configuration with blind tracks on either side communicating with the anus in the midline posteriorly, and probably result from an abscess in the postanal space.


The patient may present with recurrent perianal abscesses or with a bloody and purulent discharge. Pain and discomfort are usual. A careful history may elicit symptoms of inflammatory bowel disease or other conditions.


The diagnosis is usually confirmed by examination. An external opening is usually readily visible. The track leading to the internal opening is sometimes palpable and, with experience, the internal opening may sometimes be identified on rectal examination. Whenever possible, it is important to determine by examination the level of the internal opening in relation to the levator mechanism. Goodsall's law indicates that fistulas with an anterior external opening drain directly into the anus at the dentate line, and those with a posterior external opening take a curved course to enter the anal canal in the midline (Goodsall's law.). While the majority of fistulas probably conform to Goodsall's law, there are some exceptions.

Goodsall's law.


Sigmoidoscopy is necessary to examine the mucosa of the rectum to exclude inflammatory bowel disease. If the latter is suspected then colonoscopy and a small bowel series should be performed to determine the extent of the disease.

Examination under anaesthesia is very useful, especially in patients with complex or high fistulas. A fistulogram may be useful in identifying the extent of complex fistulas. Endoluminal ultrasound and magnetic resonance imaging (MRI) are proving very useful in patients with complex fistulas as they clearly demonstrate the relationship of the fistula track to the levator mechanism and anal sphincters.


Spontaneous healing of perianal fistula is rare. Surgical treatment is usually required. The key to management includes identification of the fistulous tracts and their relationship with the anal sphincters.

Low fistula

The mainstay of treatment is to identify the internal and external openings and to ‘lay open’ the intervening track by fistulotomy. This allows the track to heal by secondary intention. Special assessment of the adequacy of the sphincter mechanism should be considered in females who have had several vaginal deliveries because occult injuries to the anal sphincters and pudendal nerve may already be present.

High fistula

Fistulotomy is contraindicated if the internal opening is above the levator mechanism. In these patients fistulotomy would include division of the levator, which would result in incontinence. Caution should be exercised when more than one-third of the external anal sphincter needs to be divided. To avoid this serious complication it is useful to insert a seton between the two openings: silk or silastic tubing is railroaded into the track and loosely tied. The seton may act as a drain and if it is progressively tightened it may gradually divide the muscle while allowing it to heal by fibrous tissue formation. Alternatively, the seton downstages the sepsis and facilitates subsequent repair of the fistula with an advancement rectal flap. Occasionally, with more complex fistulas, a proximal stoma is constructed to divert the faecal stream, in addition to other local surgical manoeuvres.

Anovaginal and rectovaginal fistulas

Special mention is made of anovaginal and rectovaginal fistulas because they are not uncommon and are usually very distressing to the patient.


Obstetrical trauma is the most common cause. This may be related to either a tear during delivery or an inappropriately sited episiotomy (or one that may not have been expertly repaired). Other causes include trauma, radiation injury and inflammatory bowel disease (especially Crohn's disease).


The patient complains of passing flatus or faeces per vaginum. The symptom is socially and sexually embarrassing and some patients only seek advice after several years of social isolation.


The diagnosis is readily made during examination under anaesthesia.


It is usually possible either to directly repair the defect between the anorectum and vagina or to advance a mucosal-submucosal flap of rectum or vagina to cover the defect. This treatment is efficacious even in patients with Crohn's fistulas. Occasionally, a covering (diverting) stoma may be required following repair of a very complex fistula.

Anal cancer

Anal cancer is rare and represents less than 5% of all large bowel cancers. Most anal cancers are malignant epithelial tumours of the anal canal. The majority are squamous cell carcinomas (SCC). There are various additional subtypes, including cloacogenic carcinoma (transitional, basaloid, pleomorphic), adenocarcinoma of anal gland origin and malignant melanoma. The latter represent less than 1% of all malignant tumours of the anorectum. In Queensland with the highest incidence of cutaneous melanoma in the world, anorectal melanoma is the fourth more common site of occurrence after cutaneous, occular and vulval melanomas.

Squamous cell carcinomas of the anal canal occurs commonly in elderly women, while SCC of the anal verge is more often seen in men. The reason for the higher prevalence in women is unclear but it may be due to human papilloma virus (HPV) infection from secondary spread from cervical HPV (genotypes 16 and 18) or from the practice of receptive anal intercourse. Many agents may act as cofactors with HPV to promote epithelial dysplasia into invasive cancer including carcinogens (tobacco); other viral infections (HIV, herpes simplex II); immunodeficiency; and sexually transmitted diseases (syphilis, lymphogranuloma venereum, chlamydia). Also, Bowen's disease and extra-mammary Paget's disease are important premalignant skin conditions that may give rise to an invasive cancer of the anal verge. Anal cancer is now commonly seen in male homosexuals often in association with AIDS-related illnesses.

Classification of anal cancer

A knowledge of the different epithelia that line the anal canal is helpful in understanding the origin and classification of the various tumour types that may arise from the anus and adjacent perianal skin (Origin and classification of anal canal tumours.). The dentate or pectinate line (Anal canal. DL, dentate line.) is a circumferential landmark which, at the bases of the anal columns, unites the anal valves covering the anal crypts containing the openings of the anal glands (Anal canal and rectum.).

Origin and classification of anal canal tumours.

Anal canal. DL, dentate line.

Anal canal and rectum.

The epithelium lining the upper third of the canal is known as the ‘anal transitional zone’ (ATZ). It has a variable proximal extension into the lower rectum that is age-dependent (broader in the elderly) and represents the remnant of the cloacal membrane in the foetus. It consists of a mixture of stratified squamous, stratified columnar and cuboidal epithelium (so-called transitional epithelium), which blends with the typical simple columnar epithelium of the rectum. Between the dentate line and the anal verge is the pecten, which is lined by stratified squamous non-keratinised epithelium that lacks skin appendages and has few sweat glands. Below this is true skin composed of stratified squamous keratinised epithelium with sweat glands and hair follicles.

It is important to distinguish between cancer of the anal canal from that arising from the anal verge, because their treatment and prognosis are different.


Anal cancer typically presents with bleeding or symptoms of pruritus ani, such as moisture, perianal itch, a burning sensation or pain after defecation if the tumour is ulcerated and infected. It is often difficult to be certain of the diagnosis on clinical examination alone and a high level of suspicion is necessary when examining this area.

Clinical features

Cancer of the anal canal is indistinguishable from rectal cancer and usually presents as an ulcer with typical rolled edges (Squamous cell carcinoma of the anal verge.). Cancer of the anal verge also presents as an ulcer or chronic fissure. Occasionally, the perianal tissues may show a superficial palpable, irregular brownish eczematoid plaque. The diagnosis must always be confirmed by incisional biopsy. In this context, any haemorrhoidectomy specimen should always be labelled separately and sent for histological examination if cancer is suspected. In melanoma, those arising from the rectum are far less common than those arising from the ATZ.

Squamous cell carcinoma of the anal verge.

Tumour spread

Anal canal cancer grows predominantly by upward spread along the line of least resistance. Distal spread is limited as the dentate line is relatively fixed to the underlying internal anal sphincter. As it arises in the ATZ or watershed area, it may then spread via lymphatics accompanying the superior and middle rectal arteries and has a tendency to present at an advanced stage. Cancer of the anal verge is likewise slow growing and may metastasise along lymphatics that accompany the inferior rectal artery to superficial inguinal lymph nodes.


Treatment depends on location, size and extent of local spread of the tumour. Pretreatment evaluation depends on careful clinical examination. This usually implies examination under anaesthesia with biopsy of the tumour. Transanal ultrasonography will accurately determine the level of direct spread into surrounding tissues and an abdominopelvic computed tomography scan is useful in detecting distant spread prior to planning treatment.

Cancer of the anal verge is usually treated by a wide local excision with clear margins. Skin grafting may be necessary to cover the defect. A large SCC (≥2 cm) occasionally may require chemoradiotherapy. Excision of the rectum and anus (abdominoperineal excision [APE]) may be necessary for a large tumour that extends into and involves the anal canal.

Cancer of the anal canal is primarily treated by chemoradiotherapy. This now is considered the treatment of choice as such tumours have an extensive lymphovascular drainage area and local relapse is high if treated by APE alone; they are radiosensitive tumours; chemoradiotherapy ensures preservation of a functioning anus in the majority of patients; and often such patients are elderly and have associated comorbidity, placing them at a high risk for surgery. Chemoradiotherapy is still based on the original regimen developed by Dr Norman Nigro (Nigro's regimen). This protocol uses a small dose of external beam radiotherapy, which has remarkably low toxicity when combined with chemotherapy. After treatment, patients are followed closely for at least 5 years. Salvage APE is offered to selective patients who develop local recurrence or such patients may receive additional chemoradiotherapy. Up to 25% of patients will present with clinically involved inguinal lymph node metastases at the time of initial consultation. Any suspicious node must be biopsied. If involved, mobile nodes are usually treated by block dissection of the groin, while fixed nodes are better treated by radiotherapy.

The treatment of anal melanoma is controversial but usually involves APE, often with radiotherapy.


Anal cancer is commonly staged using a modified TNM classification (Modified TNM staging for anal cancer) developed by the Union Internationale Contre le Cancer (UICC). Importantly, prognosis for patients with anal canal SCC is related to tumour size, histological grade, the extent of local spread and the presence of regional lymph node metastases. Cell type is not a prognostic factor; survival rates for SCC and cloacogenic carcinoma are the same. After local excision with tumour-free margins patients generally have a good prognosis, with more than 80% surviving 5 years. Patients who show an initial complete response to chemoradiotherapy can expect up to 80% 5-year survival on completion of such treatment. The results of treatment for melanoma are poor, varying from 7% to 20% overall 5-year survival.

Pilonidal sinus

Pilonidal sinus is an acquired, chronic inflammatory condition in which hair becomes embedded in a midline pit or track, usually between the buttocks around the coccygeal region. It mainly affects young hirsute males and is almost never seen in prepubescent subjects. The sinus may consist of a single track, but commonly there may be subsidiary lateral tracks extending on either side to the buttocks. The sinuses are usually filled with hairs. Pilonidal sinuses can also occur between fingers and in the neckline posteriorly.


The presentation of pilonidal sinus can vary.

  • Asymptomatic. This is found incidentally during physical examination.
  • Abscess formation. This occurs with local pain and swelling, and systemic effects.
  • Chronic sepsis with discharge and discomfort. There are occasional episodes of abscess formation.


The diagnosis is readily made by simple observation of the sinus with or without evidence of sepsis.



Providing there is no sepsis, some patients may be treated conservatively by careful hair control using depilatory creams, regularly shaving the natal cleft and proper hygiene. Antibiotics are prescribed for acute exacerbations. The acute episode may sometimes settle simply by removing the hair.


Patients with an abscess should, in the first instance, have it drained. Some surgeons advocate injection of the track with a solution of phenol with the aim of obliterating it. Phenol is very irritating and it is important to protect the surrounding skin with petroleum jelly. Excision is the most commonly practised procedure. The principal track and subsidiary sinuses are excised. The resulting defect is then either left open to heal by secondary intention or is primarily sutured. If the defect is very large, as is occasionally the case, then a flap may be rotated to close it. Occasionally a split skin graft may also be used to close the defect.

Pruritus ani

Pruritus ani is an unpleasant yet common condition; however, it is poorly understood and often poorly managed. The patient complains of varying degrees of discomfort and itching around the anal area. No amount of scratching gives relief to the patient, who is often left anxious and frustrated. Symptoms are often more acute at night, exacerbated by the local warmth of bed clothing. Itch leads to repeated scratching with skin trauma, and further scratching leads to secondary infection and further itch.


The causes of pruritus ani are given in Aetiology of pruritus ani. A common exacerbating factor is said to be coffee, which acts as an irritant. Other predisposing conditions include diabetes, immune deficiency syndromes (HIV in particular) and, occasionally, psychological disorders. Diarrhoea of any cause can contribute to pruritus ani. However, causative or precipitating factors are identified in only 25% of patients.


A careful history and physical examination are required to exclude predisposing and associated conditions. Flexible sigmoidoscopy and proctoscopy are necessary to identify common anorectal conditions. When fungal infections are suspected, skin scrapings should be obtained for microscopic examination.


Coexistent and contributing conditions, such as diabetes, should be treated and managed first. The patient should be reassured that there is no sinister underlying pathology. Advice regarding personal hygiene is crucial. It is important that although the perineum should be clean, patients should not wash excessively lest the skin become too dry. After defecation, soft tissue or moist cotton wool pads should be used to wipe the anal area. The patient should avoid rubbing with harsh toilet paper. Cotton underwear is better than that made of synthetic material and tight clothes should be avoided. Whenever possible, hot humid conditions should be avoided. Medicated soaps should be not be used because they may exacerbate the irritation. Local application of zinc-based creams has been found to be useful, especially when the skin is very inflamed. A simple acid pH ointment, such as calamine lotion, helps to reduce the contact of the irritant with the perianal skin. Steroid-based creams may be used very sparingly in severe chronic cases, but should not be applied on a long-term basis because of toxicities with skin atrophy and superinfection. Disordered defecation such as anismus or mucosal prolapse may cause ‘after-leak’ following a bowel movement and may respond to specific treatment for these conditions.

Hidradenitis suppurativa

Hidradenitis suppurativa is a chronic, debilitating inflammatory condition of the apocrine glands. The axillae, groin, perineum and perianal skin are primarily involved. Apocrine glands begin to function at puberty and their secretions are thick and foul-smelling. It is thought that an endocrine disorder (elevated levels of androgen) leads to abnormal keratin production and obstruction of gland ducts.


Abnormal keratin plugging obstructs the ducts of the apocrine glands, which then become secondarily infected. The histopathology of hidradenitis suppurativa is usually non-specific.


The onset of disease usually coincides with puberty and mimics Crohn's disease. Clinically, the disease begins as a small, firm, subcutaneous nodule that subsequently becomes tender. The infected glands are painful and discharge malodorous fluid. The disease is characterised by remission and relapse, and is associated with significant scarring and consequent social isolation. Ultimately, the condition results in multiple subcutaneous tracks and fibrosis around the anus, and may mimic a complex fistula-in-ano (Hidradenitis of the perineum and perianal region.). Only the distal one-third of the anal canal that contains apocrine glands is involved. Other regions should always be examined, including the axillae, groins and perineum, to ensure adequate treatment.

Hidradenitis of the perineum and perianal region.

Differential diagnosis

Differential diagnosis includes:

  • lymphogranuloma venereum
  • tuberculosis
  • actinomycosis
  • pilonidal sinus
  • fistula-in-ano
  • Crohn's disease
  • squamous cell carcinoma

Evaluation of the patient includes inspection of all apocrine gland-bearing areas. Sigmoidoscopy is done to determine the extent of anal disease and to rule out Crohn's disease. If the diagnosis is in doubt, biopsy of the involved tissue is performed.



Broad-spectrum antibiotics such as augmentin are useful. Acute abscesses are drained. Long-term antibiotics do not alter the likely chronicity of the course of illness.


The treatment of choice is an en bloc excision of the involved skin-bearing apocrine glands. Minor defects may be closed primarily. However, more radical surgery usually results in a wide defect that needs to be grafted. Alternatively, incision and drainage of subcutaneous abscesses without radical excision may be done for very extensive disease. Repeated sessions may be needed to lay open all the tracks. Very occasionally, with very severe perineal disease, preliminary faecal diversion by loop colostomy may be helpful.

Perianal warts

Perianal warts, also known as condylomata acuminata, are sexually transmitted. They are most often seen in adult homosexual males and less frequently in the heterosexual population. About two-thirds of patients with perianal warts also have warts within the anal canal. Perianal warts are caused by HPV, and genotype 6 is most frequently seen. There is an association between warts, receptive anal intercourse and anal cancer. Perianal warts may become locally invasive without invasion of lymphovascular structures. These are the so-called giant condylomata.

Squamous metaplasia and in situ carcinomatous changes within the perianal warts may occur. Sometimes they become malignant and result in invasive SCC.


Treatment involves the combination of diathermy fulguration of small clusters of warts or warts within the anal canal and scissor excision of more extensively involved areas. Topical application of 25% podophyllin in benzoin tincture has a role in small isolated clusters of perianal warts but may cause pain. Several sessions may be needed to clear recurrent warts.Warts may also disappear spontaneously, presumably due to the development of some degree of immunity.

Levator syndrome

The cause of levator syndrome is obscure. Patients describe a sudden onset of severe perineal pain that is selflimiting, lasting from only a few minutes to less than half an hour, often after sexual activity or awakening from sleep (also called proctalgia fugax). It mainly affects young men and tends to regress spontaneously in later life. The majority of patients are anxious. A large number of patients also present with a ball-like rectal pressure radiating from the rectum toward the coccyx and sometimes into the buttock. This is usually aggravated by sitting and is relieved by ambulation or lying down. This occurs more frequently in women. The term levator syndrome is used to describe this entity but more often it encompasses a generalised diagnostic group with obscure causation. It is important to exclude other organic causes that may cause perineal or anal pain (Causes of anal pain). Proctalgia or levator syndrome pain should not be confused with coccygodinia, which implies pain due to a coccygeal injury. Computed tomography scan, magnetic resonance imaging as well as transanal ultrasonography are all useful techniques to investigate patients with chronic pain; however, in the majority of patients the aetiology remains obscure and is commonly explained on the basis of idiopathic, self-limiting painful spasm of the pelvic floor muscles (levator ani, puborectalis).

Treatment is empirical and patients should be reassured that they have no sinister pathology. Massage of the puborectalis sling, local heat, muscle relaxants, galvanic muscle stimulation and biofeedback have all been claimed to alleviate pain. Reassurance is often sufficient to deal with most of the symptoms. Management is difficult and recurrence rates are substantial owing to psychogenic reasons.

Anorectal manometry

Anorectal manometry is a method of measuring anal canal pressure. It may be useful in the investigation of patients with faecal incontinence and obstructed defecation. In most patients with anorectal disorders, however, anorectal manometry is not essential.

A small balloon mounted at the end of a catheter that is connected to a pressure transducer is passed into the anal canal and slowly withdrawn. Resting pressures are measured at 1-cm intervals. This permits an estimation of the length of the anal canal and measures the resting pressure, which reflects the function of the internal sphincter. The patient is then asked to contract the sphincter muscle, and the maximum squeeze pressure is measured. This is a function of the external sphincter. Sophisticated computerised equipment has been developed to provide longitudinal and circumferential pressures along the entire length of the anal canal.

When the rectum is filled with faeces, the internal sphincter should relax (the rectoanal inhibitory reflex). This does not occur in conditions like Hirschsprung's disease. To test this reflex, a second, longer cathetermounted balloon is passed into the rectum and slowly inflated, at the same time measuring the resting pressure in the anal canal. This pressure should decrease as the rectal balloon volume increases.

Anorectal manometry ascertains coordination of the pelvic floor and anal sphincters during straining at stool and simulated defecation in a laboratory setting. Paradoxical contraction of the puborectalis muscle with straining (anismus) can be demonstrated by pressure and electromyographic study of the anal canal.

Endoluminal ultrasound

During the past decade, intrarectal and intra-anal ultrasound probes have been developed to obtain accurate and detailed views of the five layers of the rectal wall and the pararectal tissues. The examination is rapid, well tolerated by the patient and accurate. Endoluminal ultrasound can be used to accurately assess the degree of invasion of tumours through the bowel wall. It is especially useful in assessing patients with villous tumours of the rectum and can assess whether a rectal cancer has invaded adjacent organs. It is less accurate in determining whether metastases to lymph nodes have occurred. Ultrasound-guided biopsies of adjacent structures can also be performed with remarkable accuracy. Endorectal ultrasound is particularly useful for pre-operative staging of low rectal tumours in determining whether patients should have abdominoperineal excision or a transanal local excision with preservation of anal sphincters. It also helps select those lesions that might benefit from pre-operative adjuvant therapy. Endorectal ultrasound is also invaluable in the evaluation of a pararectal mass because it helps define its relationship with the rectal wall.

Endorectal ultrasound is emerging as a potentially useful tool for the surveillance of patients after surgery for rectal cancer. The test may detect extrarectal recurrence or enlarged pararectal lymph nodes in the preclinical stage, at a time when therapeutic intervention may have a beneficial effect. It may also help to confirm a local recurrence when clinical examination and other tests, such as computed tomography scan, is equivocal.

Endo-anal probes are available to provide a clear view of the anal sphincters, the pelvic floor and perianal tissues. Indications for this test include the evaluation of complex or recurrent anal fistulas, faecal incontinence and anal carcinoma. An occult intersphincteric abscess (causing anal pain) may also be identified using endo-anal ultrasound (Endo-anal ultrasound showing a left-sided intersphincteric abscess.).

Endo-anal ultrasound showing a left-sided intersphincteric abscess.

Further reading

Fazio VW, Tjandra JJ. The management of perianal disease. In: Cameron JL, ed. Advances in Surgery. Vol 29. Philadelphia: Mosby-Year Book Inc; 1996:59–78.

Orsay C, Rakinic J, Perry WB, et al. Practice parameter for the management of anal fissures. Dis Colon Rectum. (In press).

Tjandra JJ, Fazio VW. Perianal disease. In: Cohen AM, Winawer SJ, eds. Cancer of the Colon, Rectum and Anus. New York: McGraw-Hill; 1995:1007–1012.

Wong S, Gibbs P, Chao M, Jones I, McLaughlin S, Tjandra JJ. Carcinoma of the anal canal: a local experience and review of the literature. Aust NZ J Surg. 2004;74:541–546.

Tjandra JJ, Lubowski D. Anorectal physiological testing in Australia. Aust NZ J Surg. 2002;72:757–759.

Schraffordt SE, Tjandra JJ, Eizenberg N, Dwyer PL. The anatomy of the pudendal nerve and its terminal branches: a cadaver study. Aust NZ J Surg. 2004;74:23–26.
Personal tools