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Anal fistulas - Kathryn Boyce
- 1. TREATMENT OF ANAL FISTULA Kathryn Boyce 03/04/13
- 2. Introduction • Aetiology • Classification • Clinical assessment • Treatment • Management of specific fistulas; Crohn’s disease
- 5. Clinical Assessment • History • Examination
- 7. Investigations • Anal manometry • Fistulography • CT • Anal endosonography • MRI
- 8. MRI
- 10. MRI
- 11. MRI
- 12. MRI
- 13. Treatment
- 14. Fistulotomy
- 15. Fistulotomy
- 16. Seton
- 17. Treatment • Transanal rectal advancement flap • Fibrin Glue • Fibrin plug
- 19. Treatment • 1. Emergency treatment: I+D of abscess • 2. Stabilisation: insertion of seton and optimisation of medical therapy • 3. attempts at healing:medical therapy including anti-TNF- alpha (infliximab, remicade) or surgery, including fistulotomy or flap procedures or both • 4. proctectomy if the above treatment fails
- 20. Association • Crohn’s disease • HIV infection • Ileoanal pouch anastomosis • Malignancy • Tuberculosis
- 21. Summary • Understand the pathological anatomy • It is not possible to be prescriptive on the management of each type of fistlua • Complex fistulas should be treated by a surgeon with experience particularly when they are associated with Crohn’s disease
- 22. References • The Treatment of Anal Fistula: ACPGBI Position Statement 26 October 2012. The Association of Coloproctology of Great Britain and Ireland. www.acpgbi.org.uk/members/guidelines/documents
- 23. Anal Canal Anatomy • Extraperitoneal • 3-5cm long • 2/3 above dentate line • 1/3 below dentate line • Uppermost portion of canal dominated by mucosal ridges called anal columns • Columns contain terminal branches of superior rectal artery and vein
- 25. Pectinate line a.k.a Dentate line • Clinically important landmark • Lies at inferiormost level of anal columns and indicates the junction of the superior and inferior parts of anal canal • Difference in embryonic origin of these parts gives rise to differing arterial, venous and nervous supply above and below the dentate line
- 27. Anal sphincters • Internal sphincter- involuntary, parasympathetic innervation, relaxes in response to pressure distending rectal ampulla • External sphincter- subcutaneous, superficial and deep parts, voluntary, S4 innervation via inferior rectal nerve (branch of pudendal nerve)
- 28. Blood supply • Upper 2/3 lined with simple columnar epithelium • Supplied by superior rectal artery (branch from IMA) • Lower 1/3 lined with stratified squamous epithelium • Supplied by inferior rectal artery (branch from internal pudendal artery) • Lower 1/3 third further divided by Hilton’s white line- division between keratinized and non-keratinized stratified squamous epithelium
- 30. Venous and lymphatic drainage • Plexus of veins branch around anal canal • Drain to superior rectal vein above dentate line • Drain to inferior rectal vein below dentate line • Drain into internal iliac lymph nodes above dentate line • Drain into superficial inguinal lymph nodes below line
- 32. Nervous innervation • Visceral supply from inferior hypogastric plexus above dentate line (therefore only sensitive to stretch) • Somatic supply from inferior rectal nerve (branches of pudendal) below dentate line (therefore sensitive to pain, temperature and touch)
- 34. Ano-rectal abscesses • Perianal- most common (60% cases) • Ischiorectal- occurs when suppuration transverses the external sphincter into ischiorectal space • Intersphincteric- suppuration between sphincters • Supralevator- results from primary disease in the pelvis or suppuration extending cranially from an origin in intersphincteric space.
- 36. Park’s classification of Fistula-in-Ano
Editor's Notes
- Common Causes pain and discharge of pus from an external opening which may be continuous or intermittent Often causing pain and discomfort making the patients life a misery
- Anorectal sepsis may present acutely as an abscess or chronically as a fistula. Non-specific anal fistulas arise as a consequence of infection developing in an anal gland lying within the intersphincteric space. A fistula consists of a primary track which passes from the internal opening in the anal canal to the external opening in the perineum. The presence of glands within the submucosa and internal sphincter was recognised in 1880. In 1961 parks carried out a study on 44 ano rectal specimens and found glands in all specimens, usually numbering 6-10. Each gland emptied into an anal crypt. In 2/3 one or more gland branches entered the sphincter and in half the cases glandular tissue crossed the internal sphincter to end in the intersphinteric space. Not all people had intramuscular glands, higher incidence in males than in females. Other authors have shown a wide variation in anatomy of anal glands and there associated ducts with many reporting a preponderance of ducts in the posterior anal canal possibly explainging the high frequency of the internal opening lying in the midline posteriorly. The role of the anal glands is not known. They are mucin secreting but the secretion appears to be of different composition to the mucin secreted by the rectal mucosa and they are dissimilar to those involved in scent production and thus they are not vestigial remnants of sexual scent glands. Although current understanding places infection of an anal gland in the intersphincteric space as the initiating event in anal sepsis, an acute abscess confined to the intersphinsteric space is rare and in most patients with an acute abscess the infection points some distance from the intersphinteric space. Spread from an infected intersphincteric gland can occur in 3 directions: Downward –perianal abscess at the anal margin acute stage or intersphincteric fistula chronic phase Laterally – penetrating the external sphincter to form an ischiorectal abscess acute or trans-sphincteric fistula chronic phase Upwards – either to form a pelvic abscess in the supralevator space or a high intramuscular abscess depending on the relationship of the infected gland to the longitudnal muscle.
- Anal fistulas should be classified on the basis of the relationship between the primary fistula track and the anal sphincter muscles. 4 types a – inter, b – trans, c – supra and d – extrasphincteric e – subcutaneous/superficial
- ?intestinal pathology ?sphincter function ?previous anal surgery ? Obstetric trauma Inspection – location of external opening Palpation-induration? DRE – internal opening?
- States that the external opening of a fistula tract located anterior to a transverse line drawn across anal verge is associated with a straight radial track to the dentate line. An external opening posterior to the transverse line follow a curved tract to the posterior midline of the rectal lumen. Not applicable in all cases – various factors inc intestinal disease confound it. Data indicate that goodsall’srule is accuurate in patients with an opening posterior to the transverse anal line but is less reliable when it is anterior.
- Anal manometry has been shown to improve outcome in selected patients – by guiding appropriate use of sphincter preserving techniques Fistulography is little used in clinical practice –in certai pts eg IBD or extrasphincteric fistula fistulography can show direct communication with the intestine above the levator. CT – offers little in the assesment of anal fistula other than to determine the extent of intestinal inflammation in inflammatory bowel disease - thin slice spiral ct may be helpful when mri is not available or iiscontraindicated Anal endosonography (us) may be the first line investigation for patients with an anal fistula suspected to be complex. Patients with recurrent fistula may benefit from anal endosonography, but mri will also be required MRI – Should be considered in any primary fistula deemed after clinical or uss assessment to be complex. It should also be considered in patients with recurrent anal fistulas. The majority of fistulas need no investigationand can be treated with surgery with good expectation of cure. Primary cases suspected to be complex should have an anal uss and if features of complex fistulation or secondary extension are present the mri should be requested
- Infection may spread circumferentially in either the intersphincteric space, ischorectal fossa or supralevator space to form a so-called horesshoe extension
- The key to successful treatment is to eradicate the primary track. In most patients this is carried out by laying open the fistula Fistulotomy. An operation which has been performed since mediaeval times as described by john of ardene in the 14th century It aims to cure the fistula while at the same time preserving anal sphincter function.
- Division of external sphincter muscle can lead to impairment of continence which is more likely the higher the fistula track
- Immediate fistulotomy is assoc with a lower recurrence rate than simple i+d but should be advised in patients in whom the internal opening can be found and where the fistula is submucosal or intersphincteric. Abscesses assoc with a more complicated fistula should be simply drained and subsequent surgery reserved for patients who develop continuing or further sepsis or fistula.
- Where it is deemed that fistulotomy would lead to disturbance of continence other procedures are available Loose seton Can be used to achieve longterm drainage Cutting – gradually severs the enclosed muscle with the aim of achieving cure of the fistula with minimal continence disturbance.
- Attempts to occlude the fistula track by biological substances
- Superior-derived from embryonic hindgut Inferior- derived from embryonic proctodeum
- Internal sphincter muscle continuation of the circular muscle of the rectum External sphincter-deep segment continuous with puborectalis muscle and forms anorectal ring (palpable on digital examination) Note ishiorectal fossa
- Between the two the middle rectal arteries form anastomoses with each to assist in the blood supply
- Middle rectal vein mainly drains muscularis externa and anastomoses with superior and inferior veins
- Perianal-superficial collections of pus located beneath the skin of anal canal, do not transverse external sphincter Supralevator- appendicitis, diverticular disease, gynae sepsis, intersphincteric space through the longitudinal muscle of the rectum and reaching above levators
- Intersphencteric- 70% of fistulas, through internal sphincter down intersphincteric space Transsphencteric- 25%, through internal and external sphincters into ischiorectal space Suprasphecteric-5% via intersphincteric space superiorly above puborectalis Extrasphincteric 1%