MEDI7302 Study Guide - Final Guide: Diverticulitis, Endoderm, Sacral Plexus

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School
Department
Course
Professor
Perianal
Learning
objectives
Understand the presentation and treatment options for rectal prolapse
Explain the cryptoglandular theory of perianal abscess development
Explain how perianal fistulae develop and understand the Salmon-Goodsall rule
Contrast the management of the three common causes of acute perianal pain,
perianal abscess, thrombosed external haemorrhoid and anal fissure
Describe a stepwise management plan for first, second and third degree
haemorrhoids
Anatomy Anal canal is the final segment of GIT that plays an important role in defecation and
maintaining faecal continence
3cm (F) or 4cm (M) canal inside the anal triangle of the perineum between R and L
ischioanal fossae
Anal sphincters
Both internal and external anal sphincters overlap
each other
Location Type Neurovascular
Internal
Upper
2/3 anal
canal
Thickened involuntary
circular smooth
muscle in bowel wall
(an extension of the
circular muscle of the
rectum)
Middle rectal
artery
PSNS fibres (S4)
External
Lower
2/3 anal
canal
Voluntary muscle
(extension of
puborectalis and
levator ani)
Inferior rectal
artery
Inferior rectal
nerves (via
pudendal nerve)
Anorectal ring - muscular ring formed by fusion of
internal anal sphincter, external anal sphincter & puborectalis muscle
Internal structure
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Superior aspect of anus (above pectinate line) has columnar epithelium
(continuation of rectum superiorly)
Mucosa is organised into longitudinal folds (anal columns) joined at their
inferior ends by anal valves, whereby small pouches sitting above anal valves called anal
sinuses contain mucus-secreting glands
Anal valves collectively form an irregular circle called pectinate/ dentate
line that divides anal canal into upper and lower parts
Above pectinate line is derived from embryological hindgut
Below pectinate line is derived from ectoderm of proctodeum
Inferior aspect of anus (below pectinate line) has non-keratinized stratified
squamous epithelium, that transitions to true skin/ keratinized stratified squamous at
inter-sphincteric groove
Surgical vs anatomical anal canal
Surgical/ functional anal canal - 4cm long, anorectal ring (proximal)
-> anal verge (distal)
Anatomical anal canal - 2cm long, dentate ling (proximal) -> anal
verge (distal)
Neurovascular supply
Above pectinate line Below pectinate line
Arterial Superior
rectal artery (branch off IMA)
Anastomosing
branches from middle rectal artery
(branch off internal iliac, anterior
div)
NOTE:
superior, middle and inferior rectal
arteries all anastomose
Inferior rectal
artery (branch off internal pudendal
artery)
Anastomosing
branches from middle rectal artery
(branch off internal iliac, anterior div)
NOTE: superior,
middle and inferior rectal arteries all
anastomose
Venous Submucosal
venous plexus -> superior rectal
vein (drain into IMA) -> portal
system
If varicosed, it
can result in internal haemorrhoids
NOTE:
superior, middle and inferior rectal
veins all anastomose to form
portal-systemic anastomoses
Submucosal
plexus -> inferior rectal vein (drain
into internal pudendal) -> IVC
(systemic system)
If varicosed, it
can result in external haemorrhoids
NOTE: superior,
middle and inferior rectal veins all
anastomose to form portal-systemic
anastomoses
Nerves Visceral
innervation (inferior hypogastric
plexus)
Sensitive to
stretch
Somatic
innervation (inferior anal nerves that
branch off pudendal nerve)
Sensitive to pain,
temp, touch, pressure
Lymphatics Internal iliac
LNs
Superficial
inguinal LNs
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Relationships
Anterior Male
P
erineal body
U
rogenital diaphragm
U
rethra
B
ulb of penis
Female
P
erineal body
U
rogenital diaphragm
V
agina
Posterior Anococc
ygeal ligament
Coccyx
and sacrum
Lateral Ischioan
al fossae
Overview of
pathology
Hematochezia
(PR bleeding)
Bright red blood passing per rectum is a common symptom
Etiology
General Bleeding diatheses (rare)
Local Haemorrhoids
Fissure in ano
Colon or rectal cancers
Diverticular disease
Ulcerative colitis
Trauma
Angiodysplasia of colon
Massive haemorrhage from upper GIT (eg bleeding
duodenal ulcer - either hematochezia + haematemesis OR meleana)
Clinical presentation
Blood Pain
Haemorrhoids Bright red blood on paper & in toilet
Possible prolapse
Painless
Pain if prolapsed & thrombosed
Fissure in ano Bright red blood on paper & outside Long lasting pain after passing stool
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Document Summary

Understand the presentation and treatment options for rectal prolapse. Explain the cryptoglandular theory of perianal abscess development. Explain how perianal fistulae develop and understand the salmon-goodsall rule. Contrast the management of the three common causes of acute perianal pain, perianal abscess, thrombosed external haemorrhoid and anal fissure. Describe a stepwise management plan for first, second and third degree haemorrhoids. Anal canal is the final segment of git that plays an important role in defecation and maintaining faecal continence. 3cm (f) or 4cm (m) canal inside the anal triangle of the perineum between r and l ischioanal fossae. Both internal and external anal sphincters overlap each other. Thickened involuntary circular smooth muscle in bowel wall (an extension of the circular muscle of the rectum) Voluntary muscle (extension of puborectalis and levator ani) Anorectal ring - muscular ring formed by fusion of internal anal sphincter, external anal sphincter & puborectalis muscle.

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