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7
Appendix Diseases
ANATOMY OF THE APPENDIX
P
SA RO
M PE
PL R
E TY
C O
O F
N E
TE L
N SE
T V
- N IE
O R
T
FI
N
AL
• Appendix develops as a diverticulum of the
cecum (cecal bud) in embryonic week 8, as part
of caudal midgut.
• Appendix is variable in length (2-20 cm) and
may become inflamed and enlarged owing to
fecal impaction and/or infection (appendicitis).
• Small mesentery (mesoappendix) connects with
terminal ileum and contains appendiceal blood
vessels and lymphatics.
• Tissue layers include mucosa, lamina propria,
inner circular and outer longitudinal smooth
muscle, and adventitia (peritoneum and
mesentery).
• Low mucosa contains numerous goblet cells,
intestinal glands, and crypts of Lieberkühn.
• Taeniae coli (triple longitudinal muscle bands of
the cecum) merge into a single, outer longitudinal muscle layer on appendix.
• Lamina propria contains masses of lymphoid
nodules with germinal centers.
Location and Position of Appendix
• Typical locations: retrocecal-retrocolic, pelvic
(descending), subcecal, ileocecal (anterior to
ileum), ileocecal (posterior to cecum)
• Variable by time and between individuals
• Can depend on size of mesoappendix
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Appendix Diseases
Ileocolic artery
Ileal branch
Superior
mesenteric
artery
Appendicular
artery
AL
Superior ileocecal
recess
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PL R
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Terminal part
of ileum
Ileocecal fold
(bloodless
fold of Treves)
Mesoappendix
Appendicular artery
Inferior
ileocecal
recess
Vermiform appendix
Appendicular
artery
Mesocolic
taenia
Retrocecal recess
Ileocecal Region and Appendix
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McBurney’s
point (on
spinoumbilical
line)
C
P
SA RO
M PE
PL R
E TY
C O
O F
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AL
A
Barium radiograph of
unusually long appendix
(A, Appendix; C, Cecum)
Variations in position
of appendix
Fixed
retrocecal
appendix
Mesoappendix
Serosa (visceral peritoneum)
Longitudinal muscle
Circular muscle
Submucosa
Aggregate lymphoid
nodules
Crypts of Lieberkühn
Vermiform Appendix
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Appendix Diseases
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Appendix Diseases
• May be displaced into pelvis in pregnancy, with
attendant differences in symptoms
Mesentery and Folds
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SA RO
M PE
PL R
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Mesoappendix
• Runs from the posterior leaf of the mesentery of
the terminal ileum
• Runs posterior to the terminal ileum and is often
attached to it
• Attaches to left side of cecum and to the entire
length of the appendix
• Triangular
• Contains appendicular artery (branch of ileocolic) and its variants
Ileocolic or Superior Ileocecal Fold
• In the terminal ileal mesentery
• Contains anterior cecal artery
• Forms anterior wall of ileocolic or superior ileocecal fossa
• Overlies terminal ileum to posterior wall of fossa
Ileocecal or Inferior Ileocecal Fold
• Anterior to mesoappendix
• Extends from right and anterior terminal ileum
• Forms anterior wall of ileocecal or inferior ileocecal fossa
• Mesoappendix: posterior wall of fossa
• Contains no vessels: “bloodless” fold of Treves
VESSELS AND LYMPHATICS
Appendicular (Appendiceal) Artery
• Branch of the ileocolic artery or of the ileal or
colic branch of the ileocolic (branches from the
superior mesenteric artery)
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• Base of the appendix may be supplied by the
anterior or posterior cecal artery.
• Appendiceal artery typically passes behind the
terminal ileum, within the mesoappendix.
Appendicular (Appendiceal) Vein
• Joins ileocolic vein, which joins superior mesenteric vein (portal vein drainage)
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PL R
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Hepatic
portal
vein
Superior
mesenteric
vein
Ileocolic
vein
Posterior
cecal vein
Appendicular
vein
Right testicular
(ovarian) vessels
External iliac vessels
Veins of Large Intestine
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Appendix Diseases
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Appendix Diseases
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PL R
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C O
O F
N E
TE L
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N
Right
colic nodes
AL
Superior
mesenteric
nodes
(central
superior
group)
Ileocolic
nodes
Prececal
nodes
Appendicular
nodes
Lymph Drainage of Large Intestine
Lymphatics
• Local drainage of nodes within mesoappendix
through vessels and nodes along appendiceal
and ileocolic arteries
• Draining toward superior mesenteric lymph
nodes
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CLINICAL CORRELATES
• Appendicitis is considered primarily a disease of
adolescents and young adults.
• Rare in infants
• Lifetime risk for Western populations is ~7%;
incidence varies with age.
Etiology (Most Common)
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Symptoms (Classic Presentation)
AL
• Children: hyperplasia, can follow infection
• Adults: fecalith
• Anorexia, periumbilical pain, vomiting
• Locus of pain shifts to right lower quadrant with
onset of peritonitis.
Differential Diagnosis
• Differential diagnosis for appendicitis is
extensive.
• Other conditions to be ruled out: other gastrointestinal, gynecologic, urologic, neoplastic
diseases.
Appendicitis during Pregnancy
• Most common cause of first-trimester acute
abdominal pain
• More likely to occur in second trimester, but not
the most common cause of acute pain
• More likely to perforate in third trimester (confused with contraction pain)
• Right upper quadrant pain can occur in third
trimester.
• Fetus can die with rupture (35%).
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Appendix Diseases
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Appendix Diseases
Acute
appendicitis
Fecal
concretions
in inflamed
appendix
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PL R
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Gangrenous
appendicitis
Inflamed retrocecal
appendix with
adhesions
Mucocele of appendix
Appendiceal abscess
Carcinoid of appendix
Diseases of the Appendix
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Prophylaxis
• Suspected, but uninflamed appendix may be
removed during laparotomy for a ruptured
ovarian cyst, thrombosed ovarian vein, or
regional enteritis (non-cecal).
Clinical Signs and Landmarks
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SA RO
M PE
PL R
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• McBurney’s point: surface projection on abdomen of appendix attachment to cecum; 1/3 of
the way along line from right anterior superior
iliac spine to umbilicus; near anterior cutaneous
branch of iliohypogastric nerve
• McBurney’s sign: deep tenderness at McBurney’s
point
• Aaron’s sign: rebound pain with applied
pressure
• Most common site of appendicular perforation:
midpoint of antimesenteric border
CT Signs of Appendicitis
• Diameter >7 mm or wall thickness >2 mm
• Bull’s eye appearance
Surgical Appendectomy
• Gold standard remains exploratory laparotomy
and appendectomy
• McBurney approach: oblique incision divides
external oblique fascia parallel to its fibers
• Rocky-Davis incision: right lower quadrant
transverse incision may be preferred in specific
instances
Carcinoid of the Appendix
• Most common site for carcinoid tumor (~50%)
• Ileum and rectum next most common sites
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Appendix Diseases
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