Anal fistula pathophysiology

Anal fistula Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Anal fistula from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Diagnostic study of choice
Laboratory Findings
X Ray
Electrocardiogram
CT
MRI
Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
Anal fistula pathophysiology On the Web
Most recent articles
cited articles
Review articles
CME Programs
Powerpoint slides
Images
American Roentgen Ray Society Images of Anal fistula pathophysiology All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Anal fistula pathophysiology
CDC on Anal fistula pathophysiology
Anal fistula pathophysiology in the news
Blogs on Anal fistula pathophysiology
Directions to Hospitals Treating Anal fistula
Risk calculators and risk factors for Anal fistula pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Manpreet Kaur, MD [2]

Overview

Anal fistula develops from infection of anal crypts gland.

Pathophysiology

Anatomy

• The anal canal is a 2 to 4cm in length, starts at the anorectal junction to the end of anal verge.
• It is divided into an upper and a lower part by transition zone that is seen at the dentate line or pectinate line which is surrounded by longitudinal mucosal folds, called columns of Morgagni.
• Each of this fold contains anal crypts, each of which contains 3 to 12 anal glands, the distribution of these glands is not uniform with most of the glands present anterior to the position of the anal canal and fewer in the posterior position.

Pathogenesis

There are following steps in the formation of anal fistula:

• Anal fistula develops from infection of anal crypts gland.

• The initial infection occurs in the ducts of the anal glands and the spread of infection results in the formation of the abscess.
• The crytoglandular theory states that obstruction of anal gland duct results in a infection
• The presence of these glands deep in relation to the anal canal and sphincter, the infection follows the path of least resistance resulting in abscess formation at the termination of the gland.

• If the abscess is ruptured, a fistula is formed.

Associated Conditions

Anal fistulas are associated with following conditions:

• Diverticulitis
• Foreign-body reactions
• Actinomycosis
• Chlamydia
• Lymphogranuloma venereum (LGV)
• Syphilis
• Tuberculosis
• Radiation exposure
• HIV disease
• Crohn’s disease
• Pilonidal disease
• Hidradenitis suppurativa
• Trauma
• Previous surgery (including ileoanal pouch surgery)
• Presacral dermoid cysts
• Sacrococcygeal teratoma
• Rectal duplication

Gross Pathology

On gross pathology:

• They are seen linear or completely maloriented and have the epithelial lining at one of its edges.

Microscopic Pathology

On microscopic histopathological analysis, following features are found:

• There is the central core of active and chronic inflammation with granulation tissue, foreign body giant cells, and surrounded by scar.
• Granulomas are seen occasionally.
• There is squamous cell extend into the fistula track which is partially epithelialized.