Benign Colorectal Conditions

 

• Anorectal anatomy

  Rectum

  • 15 cm long, from rectosigmoid to anorectal line. Curves with sacrum, and contains 3 folds.
  • Autonomic innervation from hypogastric plexus.

  Anal canal

  • 3.5 cm long, from anorectal line to anus.
  • Divided by dentate line, with columnar epithelium and autonomic innervation above, and squamous epithelium (continuous with perianal skin) and pudendal somatic innervation below.

  Sphincters

  • Lie within anal canal.
  • Internal sphincter is a circular muscle under parasympathetic control.
  • External sphincter blends with puborectalis, and is under voluntary control via the pudendal nerve (S4).

• Anorectal abscess

  Pathophysiology and anatomy

  Obstruction of anal glands/crypts – 6-10 structures at the dentate line of unclear function – and subsequent infection by gut bacteria.

  Locations:

  • Perianal (60%): limited to skin of anal canal.
  • Ischiorectal (20%): crosses the external anal sphincter.
  • Intersphincteric: between internal and external sphincters.
  • Supralevator: superior extension above levator ani. Rare.

  Abscess rupture, spontaneous or surgical, leads to fistula formation in 50%.

  Risk factors

  These may cause abscess formation via anal gland infection and/or separate mechanisms:

  • Bowel inflammation: IBD (esp. Crohn's), diverticulitis, TB, hidradenitis suppurativa.
  • Immunosuppression: diabetes, HIV.
  • Trauma: rectal foreign bodies, receptive anal sex.
  • Demographic and social: male, age 20-60.

  Presentation

  • Perianal pain and pruritus. Pain may be worse on sitting and defecation.
  • Constipation due to painful defecation.
  • Deeper abscesses may cause systemic symptoms.
  • On examination, perianal swelling (external or felt by DRE), purulent/bloody discharge. Examination under anaesthesia if there is significant discomfort.

  Investigations

  • Can often be diagnosed clinically.
  • Deeper abscesses may require endoanal US or MRI.

  Management

  Incision and drainage:

  • Can be done in ward/ED for simple perianal abscesses, otherwise will require theatre.
  • Most wounds can be left open, without packing. Intersphincteric abscesses may require post-op drain.
  • Post-procedure, advise frequent sitz baths (water to hip height) and consider laxative to reduce painful defecation.

  Antibiotics (in addition to I&D) only if there is evidence of sepsis, extensive cellulitis, or immunosuppression.

• Anal fistula

  Definition and causes

  A fistula is an abnormal communication between two epithelial surfaces. In this case, the anal canal and the perianal skin.

  Most follow drainage or rupture of an anorectal abscess (i.e. anal gland infection). Other causes include:

  • Crohn's
  • Infection: TB, HIV, actinomycosis, lymphogranuloma venereum.
  • Rectal cancer or radiotherapy.
  • Trauma: foreign body, iatrogenic, anal fissure.

  Classification: intersphincteric (70%), transphincteric (25%), suprasphincteric, extrasphincteric.

  Signs and symptoms

  Presentation:

  • Persistent symptoms or 'non-healing' following abscess drainage.
  • Rectal pain, which may be worse on sitting and defecation.
  • Discharge (continuous or intermittent) and soiling.
  • Pruritus
  • Untreated, can cause sepsis, and anatomical changes leading to incontinence.

  Examination:

  • Goodsall's rule: posterior external opening tracks along curvilinear path to posterior midline position, while anterior external opening tracks radially to anal canal.
  • Examination under anaesthesia if there is significant discomfort.

  Investigations

  • Simple fistulas can be diagnosed clinically.
  • Otherwise, MRI or endoanal US.

  Management

  Low fistula tract (superficial, intersphincteric, low transphincteric) options:

  • Fistulotomy, in which fistula is opened and allowed to heal by secondary intention.
  • Injection of fibrin glue/sealant.

  High fistula tracts options:

  • Fistulotomy and placement of seton cord, which is left in fistula to allow drainage during healing.
  • Advancement flaps: adjacent mucosa used to seal internal opening.
  • Fistula plug.
  • Ligation of intersphincteric fistula tract (LIFT).

• Anal fissure

  Definition and causes

  • Longitudinal tear (ulcer) in the anal canal, anywhere from below the dentate line to the anal margin. 90% are in the 6 o clock position.
  • Causes: straining in constipation, childbirth trauma, IBD.

  Management

  Initial advice:

  • Avoid straining.
  • Minimize constipation: increase fibre and fluid intake, consider laxative.
  • Immerse anus in warm water with shallow bath or Sitz bath kit, 2-3 times daily.

  Topical medical treatment:

  • GTN 0.4% is 1st line.
  • Other options: diltiazem 2%, Botox.

  Surgical:

  • Lateral anal sphincterotomy, in which internal sphincter fibres are divided over the length of the fissure.
  • Further option is excision and anal advancement flap.

• Haemorrhoids

  Definition and anatomy

  Enlarged, symptomatic anal vascular cushions. They are not just 'dilated veins'.

  Anal vascular cushions (aka haemorrhoidal cushions):

  • Part of normal anatomy, containing arteriovenous channels – that connect superior rectal artery and vein – sitting within smooth muscle, submucosal fibroelastic connective tissue, and mucosa.
  • Usually positioned at 3, 7, and 11 o'clock (in the lithotomy position). Smaller, additional ones may develop in haemorrhoids.
  • They contribute to anal tone.

  Risk factors

  • Middle age.
  • Constipation
  • Pregnancy

  Classification

  Grades of internal haemorrhoid:

  1. Never prolapse.
  2. Prolapse and reduce spontaneously.
  3. Prolapse and require manual reduction.
  4. Irreducible

  External haemorrhoids originate below the dentate line.

  Signs and symptoms

  • Bright red bleeding, usually on toilet paper or surface of stool.
  • Itchy but usually painless, though thrombosed external haemorrhoids and prolapsed, strangulated internal haemorrhoids may be painful and present acutely.
  • Mucus or faecal soiling may occur, though in general changes in bowel habit are uncommon and should alert you to other causes.

  Investigations

  • DRE
  • Proctoscope for examining the haemorrhoids.

  Management

  Non-Interventional:

  • Reassure, avoid straining, soften stools (fibre and fluids).
  • Topical local anaesthetic cream.
  • Sufficient for most.

  Interventional:

  • Indicated if thrombosed, strangulated, or symptomatic despite other measures.
  • Excision for painful, thrombosed external haemorrhoids presenting within 72 hrs (when pain still at peak).
  • Rubber band ligation via endoscopy for grade 1-2. Effective for 18 months. Cannot be done for external haemorrhoids as they have a normal sensory supply.
  • Open haemorrhoidectomy: post-op very painful for 2 weeks and small risk of impaired continence, but has low recurrence rate.
  • Stapling or haemorrhoid arterial ligation: for grade 1-3. Less pain than open, especially ligation, but less effective for long term prevention.

• Rectal prolapse

  Definition and types

  • Protrusion of rectum through anal opening.
  • Can be partial – mucosa only – or complete, involving full thickness of rectum. The other type is internal (intussusception).
  • Mostly in post-menopausal women.

  Signs and symptoms

  Mass that appears on defecation.

  Management

  Conservative:

  • Avoid straining.

  Mucosal prolapse:

  • Rubber band ligation or stapling.

  Full thickness prolapse:

  • Perineal approach: mucosal resection and muscle plication (DeLorme's procedure), or full thickness rectal resection (Altemeier's procedure). Gives 5-10 years relief.
  • Abdominal approach: laparoscopic ventral rectopexy, in which rectum is stitched to wall.

• Faecal incontinence

  Causes

  • Obstetric trauma: ↑parity, instrumental delivery, episiotomy.
  • Lower GI surgery.
  • Colonic or perianal disease, including cancer, fistulas.

  Investigations

  • DRE
  • Flexi sig or colonoscopy.
  • Endoanal US.
  • Anorectal physiology.

  Management

  • Treat underlying cause.
  • Anti-diarrhoeals: loperamide, codeine.
  • Anal plug.
  • Surgical: sphincter repair, sacral nerve stimulation, or stoma.

• Anal itching

  Aka pruritus ani.

  Causes

  Usually idiopathic, otherwise:

  • Colorectal: diarrhoea, constipation, haemorrhoids, fissures, fistulas, cancer, prolapse.
  • Dermatological: eczema, psoriasis, lichen planus, lichen sclerosis.
  • Infection: candida, anogenital warts (condyloma acuminata), tinea cruris, gonorrhoea, threadworm (usually nocturnal itch).
  • Inflammatory: Crohn's, hidradenitis suppurativa.
  • Multisystem: diabetes, thyroid disease, liver disease, polycythemia vera.

  Management

  Identify and treat any underlying causes.

  Patient advice:

  • Avoid itching and excess wiping, washing with plain water and gently patting dry.
  • Identify and avoid triggers e.g. soaps, detergent, fabrics, constipation, faecal leaking (try cotton wool plug).

  If perianal skin inflamed, offer 1-2 weeks 1% hydrocortisone, provided no fungal infection present.