An introduction to the ano-rectal region

The perianal, anal and rectal region lend themselves to early clinical diagnosis without the need to resort to complex investigative processes.

Procedures

The history followed by inspection, palpation, rectal examination, proctoscopy and then sigmoidoscopy are sufficient to clinically diagnose most conditions.

If a full local examination is not performed a delay in diagnosis of conditions such as carcinoma of the anal canal and rectum may occur.

Inappropriate treatment of other conditions such as pruritus ani, warts, haemorrhoids, polyps, abscesses and fistulas may result.

Functional unit of continence

The anus, anal canal and rectum are a functional unit responsible for the maintenance of continence of faeces and flatus as well as the co-ordinated process of defecation.  Theories such as the valvular mechanism of the anorectal angle have been postulated to explain the process.  Basic factors responsible for the maintenance of continence are the:

– internal sphincter
– external sphincter
– anorectal angle (formed by the puborectalis muscle)

This is all controlled by a reflex interaction and integration between the:

– sensory receptors in the pelvis
– smooth muscle internal sphincter supplied by the autonomic nervous system and
– striated muscle of the external sphincter – supplied by the somatic fibres of the pudendal nerve.  It is postulated at rest with the faeces in the rectum that the anorectal angle acts like a valve.  As pressure increases the valve is accentuated, maintaining continence.  However as the bulk increases further receptive relaxation of the internal sphincter occurs.  There is a sampling of the faecal material by the sensitive epithelium of the anal canal resulting in the desire to defecate and the sensation of the need to pass flatus

This is further controlled by the voluntary external sphincter muscle

Defaecation

With straining the anorectal angle is reduced and straightened, the internal and external sphincter muscles relax and defecation occurs.

Pathological

Continence may be interfered with as a result of localised or generalised disease or following trauma or surgery.

Histological features

The perianal skin is stratified squamous epithelium with keratinisation.  Just above the anal verge the skin, hair, sebaceous glands and sweat glands and there is a transitional type of epithelium for a distance of approximately 1 cm – to the pectinate line.

Above the pectinate line the glands of Lieberkuhn’s and goblet cell appear a muscularis mucosa and lamina propria are found.

The pectinate line (dentate line):

  • is formed at the site of the fusion of the embryonic proctodermal plate and post-allantoic gut embryologically.

  • is land mark not only histologically but is also the site at which there are major practical significant changes as is a junctional zone between:

  • the somatic sensory supply to the skin, modified skin and the autonomic supply to the mucosa above the pectinate line.

  • the junction between the haemorrhoidal arterial supply derived from the mesenteric artery and the lower pudendal artery supply from the iliac artery

  • systematic circulation below the dentate and portal venous system above.

  • lymphatic drainage below the dentaline is to the inguinal node above the dentaline to the pelvic lymph nodes – there is some overlap with this particularly in pathological states

  • anal glands open at the pectinate

History & Examination

Symptoms indicate disease but a more detailed analysis then indicated the diagnosis:

  • bleeding

  • pain

  • protruding or prolapsing lump

  • discharge – starting on the underwear or associated bowel action with pus and mucous

  • an irritation

  • faecal incontinence

  • unsatisfied defecation

  • changes in bowel habit and urgency with either diarrhoea or constipation

  • “Haemorrhoids” – often patients complain of “haemorrhoids”

The diagnosis of haemorrhoids cannot be taken at face value as patients often use this term for any anorectal problem.

All the above symptoms may be associated with:

  • disease in the anorectal region

  • disease from higher level in the bowel

  • result of some generalised problem

The history and examination are directed at differentiating these possible signs:

  • the type of bleeding is critical and needs further description, the blood may be dark or bright, mixed with the stool, on the paper or dripping in the bowl.  The bleeding may be associated with pain or painless.

  • blood mixed with the stool can suggest a cause of bleeding higher up in the bowel.

  • bright red blood on the toilet paper suggests haemorrhoids.

  • black stools may indicate bleeding from higher in the stomach.

  • a few drops of blood associated with severe pain on and after defecation could suggest a fissure.

  • the presence of pus or mucous might suggest an inflammatory condition.

  • a sexual history may be necessary to diagnose HIV or AIDS or gonococcal disease.  Infected proctitis can occur in either.  This needs to be differentiated from non-specific proctitis.

These inflammatory conditions can present with an abscess or fistula, an atypical fissure, which is of an opportunistic infection such as amoebiasis or cryptos porous.

Examination

  • A general inspection.  The general appearance of the patient may suggest a cause of bleeding and its severity.  It may be signs of pallor with excessive bleeding due to anaemia or jaundice for example where there are liver problems.  There even may be signs of cachexia.

  • The examination of the abdomen is carried out first to detect masses or other features such as an enlarged liver e.g. the liver of psoriasis may be associated with portal hypertension and bleeding haemorrhoids.

  • The left lateral position may be used for the examination.

  • The rectal examination may be difficult in the apprehensive, sensitive, overweight patient with severe pain.  An examination under anaesthesia is required in some circumstances:

  • the anal verge is inspected.

  • the anal skin has ridges which irradiating peripherally.  The anal orifice is usually closed but a gaping sphincter may be present.

  • the surrounding area is examined.

  • there may be signs of ulceration, irritation, excoriation, swelling or the external opening of a sinus or fistula with a discharge.  Skin tags are often present and may point to underlying haemorrhoids or fissures.

  • scars from obstetric injuries or trauma or previous surgery can be important in the assessment – particularly of incontinence.

  • a protruding lump may be present.  The commonest cause of this would be haemorrhoids.

Several different types of polyps may be present – particularly if the patient is asked to strain or they may be prolapsed down from the rectum by the examining finger on rectal examination.

  • a pedunculated fibro epithelial polyp

  • a pedunculated tubular adenoma

  • a sessile villous tumour

  • a myeloma or other connected tissue tumour such as a lipoma

  • Even a malignancy can be protruding

  • there may be skin lesions such as rarely melanoma, but occasionally conditions such as squamous cell carcinoma in situ.

Haemorrhoids, polyps or a rectal prolapse may appear with straining.

Abnormal laxity or descent of the perineum may occur in disorders of the pelvic floor, which can be associated with incontinence.

The anal verge can then be gently parted to demonstrate any protruding lesion or the presence of an anal fissure.  Parting the anal verge may be painful with an anal fissure and the sphincter can be seen to contract with the pain.

Rectal Examination

Rectal examination is part of the routine examination for any abdominal or rectal problem.  The glove must be well lubricated first.  An explanation is given regarding the examination and the patient reassured.  Gentle pressure is applied over the anus and this tends to overcome spasm and resistance and allows the gloved finger into the anal canal without pain.  The finger is introduced posteriorly along the anal canal and the tone of the sphincter is assessed.  The walls of the anal canal are palpated.  Four to five centimetres into the anal canal is the upper level of the surgical anal canal.  The ridge of the anorectal ring can be palpated.  The finger then enters the rectum.

The finger palpates the mucosa thoroughly and then two specific structures are sought:

  • Anterior – the prostate in males.  The cervix and uterus in females

  • Posteriorly – the hollow of the sacrum and

  • Laterally – the lateral ligaments and pelvic lymph nodes

  • The tip of the finger palpates the Pouch of Douglas looking for a mass – for example secondary deposits or a pelvic abscess.

Palpation of the mucosa may detect lesions such as:

  • Benign polyps – pedunculated tubular adenomas or sessile villous adenomas

  •  Malignant lesions such as carcinoma of the anus or rectum – ulcerated or nodular

  • Anal papillae

  • The internal opening of a fistula

Haemorrhoids may be palpated as a soft cushion but are not readily palpable unless very large or thrombosed.  If a painful condition such as an abscess or fissure is present, resistance to examination by the patient will be obvious and should not be pursued.

On withdrawal of the glove this is inspected for the presence of blood or mucous land the colour of the faecal material.

The rectal examination should be performed before any instrumentation.

Proctoscopy & Sigmoidoscopy

The mucosa is visualised and this is particularly useful in the diagnosis of haemorrhoids.  The haemorrhoids will bulge into the lumen of the proctoscope as it is withdrawn and the patient is straining.

Procedures such as injection of haemorrhoids or rubber band ligation can be performed through a proctoscope.

Sigmoidoscopy

Sigmoidoscopy can be performed in the left lateral position.  It is usually a little uncomfortable particularly when the area is inflated but is usually readily tolerated.  The area is inflated to allow visualisation of the mucosa or lumen or when attempting to negotiate the rectosigmoid junction which is at the level of 15 – 18 cms.

 It may not be possible in about 50% of patients to pass the rectosigmoid junction which is at about 15 cms due to discomfort because of the angulation to the site.

Sigmoidoscopy shows mucosal changes – signs of inflammation, melanosis coli (patchy dark pigmentation) attributable to excessive uses of laxatives and lesions arising from the mucosa such as polyps or malignancies.  These may be biopsied as necessary.

A high percentage of bowel tumours occur within reach of the sigmoidoscope.  Sigmoidoscopy is one of the most cost effective ways of detecting the presence of any carcinoma.  It should be used more frequently especially as bowel cancer is the second most common cancer in males and females.

Up to 50% of polyps and carcinomas of the colon are within reach of the sigmoidoscope.

Further investigation of the region may include flexible sigmoidoscopy, sigmoidoscopy and barium anaemia.

Management of ano-rectal conditions

Some of the conditions may be treated with conservative or appropriate ointments or creams.

Many of the conditions can be treated in the office – such as haemorrhoids.  Injection sclerotherapy and rubber band ligation are effective ways of treating haemorrhoids.  Perianal haematomas may be incised or excised under Local Anaesthetic.  A small perianal abscess can be drained.  Skin tags can be removed.

Experienced Surgeons may treat the more complex conditions in the office.  Anal fissures can be treated with sphincterotomy under Local Anaesthetic.  A variety of degrees of haemorrhoids may be excised under Local Anaesthetic in the office as appropriate.

Even polyps may be pulled down and ligated.

The same techniques can be used in hospital with the addition of light sedation.  Many cases can be treated as a day case.

Thus after a comprehensive examination of the history and examination which includes the abdomen, inspection of the perianal region, palpation of the perianal region, rectal examination, proctoscopy and sigmoidoscopy, a plan of action can be carried out.

 This may involves further investigative procedures or surgery in hospital.  However in many cases a definitive diagnosis can be made and a treatment carried out at that time or arranged for the near future.

Other serious problems must not be overlooked and must be taken into account before instituting a plan of action.

It must be remembered when treating the anorectal region the patients are apprehensive, may fear the presence of a possible cancer and may find the examination embarrassing and uncomfortable.  This needs to be assessed thoroughly before attempting any procedures.  There must be some explanation of the possibility of pain in the post-operative period.

Of course it is part of a risk management plan.  The advantages and disadvantages of having a procedure are discussed and the alternative methods of treatment available also discussed.

The option may be to do nothing or to wait and see.  A further review may be judicious.

It is however helpful to have literature available for the patient to read which will explain their condition in detail.