Space
Ischioanal fossa
Compressible tissue beside the anal sphincters
High-yield
The pudendal canal lies in obturator fascia laterally. Posterior communication between the fossae helps explain horseshoe spread of some anorectal infections.
Overview
Each ischioanal fossa is a fat-containing space between pelvic floor and lateral perineal wall. Its wedge-shaped cross-section accommodates anal movement and expansion. Inferior rectal vessels and nerves traverse the fat to reach the sphincter region.
Reference facts
- Boundaries
- Medially bounded by levator ani and external sphincter; laterally by obturator internus fascia and ischial tuberosity. Skin forms the base, and the roof narrows where pelvic floor meets obturator fascia. An anterior recess lies above the perineal membrane.
- Contents
- Fat, connective tissue, lymphatics and inferior rectal neurovascular branches; cutaneous sacral branches may also pass through. Pudendal nerve and internal pudendal vessels occupy the lateral-wall canal.
- Communications
- Extends forward above the perineal membrane and communicates posteriorly through the deep postanal region. The pudendal route connects the lateral wall with the lesser-sciatic-foramen region.
Clinical correlation
Anal-gland infection can extend into ischioanal tissues and across the deep postanal region. Horseshoe collections reflect this communicating anatomy; infection cannot be explained simply by labeling the fat poorly vascularized.
Frequently asked questions
What are the boundaries of the ischioanal fossa?
Medially bounded by levator ani and external sphincter; laterally by obturator internus fascia and ischial tuberosity. Skin forms the base, and the roof narrows where pelvic floor meets obturator fascia. An anterior recess lies above the perineal membrane.
What does the ischioanal fossa contain?
Fat, connective tissue, lymphatics and inferior rectal neurovascular branches; cutaneous sacral branches may also pass through. Pudendal nerve and internal pudendal vessels occupy the lateral-wall canal.
What does the ischioanal fossa communicate with?
Extends forward above the perineal membrane and communicates posteriorly through the deep postanal region. The pudendal route connects the lateral wall with the lesser-sciatic-foramen region.