What is the diagnosis for a patient with perianal discharge, history of perianal abscess (anorectal abscess) drained twice, cord-like structure on digital rectal examination (DRE), internal opening at the dentate line on proctoscopy, without swelling, fever, or leukocytosis (elevated white blood cell count)?

Diagnosis: Intersphincteric Fistula (Answer C)

This patient has an intersphincteric fistula, characterized by the cord-like structure on DRE and internal opening at the dentate line, representing the chronic phase of recurrent perianal abscesses. 1

Clinical Reasoning

Key Diagnostic Features Present

• History of recurrent perianal abscesses (drained twice over 2 years) strongly indicates fistula formation, as approximately 40-50% of perianal abscesses develop into fistulas 2, 3
• Cord-like structure on DRE represents the fibrotic fistula tract between the internal and external sphincter muscles, pathognomonic for intersphincteric fistula 1
• Internal opening at the dentate line on proctoscopy is the hallmark of cryptoglandular fistulas originating from infected anal glands in the intersphincteric space 1, 3
• Absence of acute infection (no swelling, fever, or leukocytosis) confirms this is a chronic fistula rather than active abscess 1

Anatomical Classification

The Parks classification system uses the external sphincter as the reference point 4:

• Intersphincteric fistulas run between the internal and external anal sphincter muscles 1
• Perianal fistulas are superficial, low-lying tracts without specific anatomic localization—too nonspecific for this presentation 4
• Ischiorectal fistulas penetrate through the external sphincter into the ischioanal/ischiorectal space, which would present differently with lateral extension 4, 1
• Supralevator abscesses occur above the levator ani muscle and would present with a palpable mass or induration superiorly, not a simple cord-like structure 4, 1

Pathophysiology

• The cryptoglandular hypothesis explains that infection begins in anal glands at the dentate line, spreads into the intersphincteric space causing abscess, then forms a chronic fistulous tract after drainage 1, 3
• The internal opening at the dentate line and intersphincteric location of the tract confirm this cryptoglandular origin 1

Critical Clinical Pearls

• Rule out Crohn's disease in any patient with recurrent perianal fistulas—obtain focused history for inflammatory bowel disease symptoms (diarrhea, weight loss, abdominal pain) 4, 1
• Intersphincteric fistulas below the dentate line can typically be treated with fistulotomy without significant risk to continence 3, 5
• The two-year history with recurrence after drainage alone (without fistulotomy) explains the persistent symptoms 3, 6