The Ischiorectal Fossa

THE ISCHIORECTAL FOSSAS-IV RM21

Learning objective

•At the end of the lecture the student should be able to:

–Know the details of ischiorectal fossa

–Identify the boundaries and recessess of ischiorectal fossa

–Know the contents of ischiorectal fossa.

•Wedge shaped spaces between skin of anal region and pelvic diaphragm

•Base directed downwards to the surface of the perineum

•Apex at the line of meeting of the obturator and anal fascia

•5 to 6 cm deep, anterioposteriorly 5 cm, 2.5 cm side to side

•Lie below the levator ani muscles and on either side of anal canal

•Post anal space connects the two fossae posteriorly by a horse shoe path. The space is filled with loose areolar tissue and loosely arranged large loculi of fat. The infection of this space leads to abscess formation and are least painful because swelling can occur without tension.

Base is formed by the skin.

Apex - Is formed by meeting of Obturator fascia with the inferior fascia of the pelvic diaphragm (anal fascia). The line corresponds to the origin of levator ani from the lateral pelvic wall.

Anterior wall - The fossa is limited by the posterior border of perineal membrane.

Posterior wall- (a) lower border of the gluteus maximus and (b) Sacro tuberous ligament
Lateral wall is vertical and is formed by

(a) Obturator internus with Obturator fascia,

(b) Medial surface of ischial tuberosity below the attachment of Obturator fascia.

Medial wall - Slopes upwards and laterally and is formed by

(a) External anal sphincter with fascia covering it in the lower part and

(b) levator ani with anal fascia in the upper part.

RECESSES

•These are narrow extension of the fossa beyond its boundaries.

•1. Anterior recess - Extends forwards above the urogenital diaphragm almost up to the posterior surface of the body of pubis.

•2. Posterior recess - It is smaller than anterior recess. It extends deep to sacrotuberous ligament.

•3. Horse shoe recess (deep post anal space/Post Sphincteric space) - Connects the two fossae behind the anal canal

•

CONTENTS OF ISCHIORECTAL FOSSA

Inside Alcock's canal, on the lateral wall

•Internal pudendal artery

•Internal pudendal vein

•Pudendal nerve

Outside Alcock's canal, crossing the space transversely

•Perineal branch of fourth sacral nerve

•Perforating cutaneous branch of S2, S3 nerve

•Inferior rectal artery

•Inferior rectal vein

•Inferior anal nerves

•Fatty tissue across which numerous fibrous bands extend from side to side