Ischiorectal Abscess


Ischiorectal Abscess, Ischioanal Abscess, Horseshoe Ischiorectal Abscess

  • Epidemiology
  1. Represents 25% of Perirectal Abscess
  • Pathophysiology
  1. Perirectal Abscess involving ischiorectal space or fossa
    1. Space contains primarily adipose tissue
  2. Anatomic boundaries
    1. Lateral to external anal sphincter
    2. Medial to the obturator internus Muscle
    3. Below or inferior to the pelvic diaphragm or levator ani (puborectalis, pubococcygeus, and iliococcygeus Muscles)
  3. Horseshoe Abscess
    1. Abscess between the anal canal and the Sacrum extends anteriorly and bilaterally into the ischiorectal space
  • Signs
  • Low Abscess
  1. See Perirectal Abscess
  2. Infection of fatty tissue below Rectum
  3. Perianal tenderness and swelling 2-3 cm from anal verge
  • Differential Diagnosis
  1. High Abscess
    1. Pelvirectal Abscess
    2. Intersphincteric Abscess
  2. Low Abscess
    1. Perianal Abscess (immediately adjacent to anal verge)
  • Imaging
  1. CT Pelvis
  2. Intrarectal Ultrasound
    1. Evaluation of complex or suspected high abscess
  • Management
  1. See Perirectal Abscess
  2. Ischiorectal Abscess incision should be made as close to anal verge as possible
    1. Minimizes length of potential fistula formation
  3. Local Incision and Drainage indications
    1. Low abscess without signs of higher spread
    2. Non-toxic appearance
  4. Surgical Consultation for drainage indications
    1. Signs of fasciitis and deep ischiorectal spread
    2. Horseshoe abscess drainage is complex
      1. Posterior incision placed between Coccyx and anus
  • Complications
  • Deep spread of infection
  1. Posterior rectal space infection (horseshoe abscess)
  2. High Ischiorectal Abscess
  • References
  1. Marx (2002) Rosen's Emergency Medicine, p. 1952
  2. Roberts (1998) Procedures, Saunders, p. 649-51
  3. Sherman, Bahga and Vietvuong (2022) Crit Dec Emerg Med 36(7): 23-9