II. Epidemiology

  1. Represents 25% of Perirectal Abscess

III. 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

IV. 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

V. Differential Diagnosis

  1. High Abscess
    1. Pelvirectal Abscess
    2. Intersphincteric Abscess
  2. Low Abscess
    1. Perianal Abscess (immediately adjacent to anal verge)

VI. Imaging

  1. CT Pelvis
  2. Intrarectal Ultrasound
    1. Evaluation of complex or suspected high abscess

VII. 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

VIII. Complications: Deep spread of infection

  1. Posterior rectal space infection (horseshoe abscess)
  2. High Ischiorectal Abscess

IX. 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

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Related Studies

Ontology: Ischiorectal abscess (C0149816)

Concepts Pathologic Function (T046)
ICD10 K61.3
SnomedCT 155795000, 266529008, 36046008
Dutch ischiorectaal abces, abces; ischiorectaal, ischiorectaal; abces, Ischiorectaal abces
French Abcès ischio-rectal
German ischiorektaler Abszess, Ischiorektalabszess
Italian Ascesso ischiorettale
Portuguese Abcesso isquiorrectal
Spanish Absceso isquiorrectal, absceso isquiorrectal (trastorno), absceso isquiorrectal
Japanese 坐骨直腸膿瘍, ザコツチョクチョウノウヨウ
English ischiorectal abscess (diagnosis), ischiorectal abscess, Abscess - ischiorectal, Ischiorectal abscess, Ischiorectal abscess (disorder), abscess; ischiorectal, ischiorectal; abscess
Czech Ischiorektální absces
Korean 궁둥뼈직장 고름집(농양)
Hungarian ischiorectalis tályog