For Pathology students

1. Acute Appendicitis
Dr Mohammad Manzoor Mashwani

2. Appendix: NORMAL STRUCTURE
The appendix is a blind-ending tubular
diverticulum of the cecum, usually lying
behind the caecum and varies in length from 4
to 20 cm (average 7 cm).The wall of the
appendix consists of all the four typical coats
of the digestive tube: mucosa, submucosa,
muscularis externa & serosa.
A diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body.

3. Histology
The appendix is characterized by a thick wall but
a relatively narrow lumen which is stellate or
irregular in outline. Intestinal villi are absent.
Mucosa: Epithelium, Lamina propria, muscularis
mucosa
Epithelium: The mucosa is lined mainly by
absorptive cells (enterocytes) which are
columnar cells; only a few/numerous goblet
cells are present.

4. Histology
The lamina propria shows intestinal glands (crypts of
Lieberkühn). The intestinal glands in the appendix are
less well developed, shorter, and often spaced farther
apart than those in the colon.
The lamina propria of the appendix is heavily infiltrated
with lymphocytes and contains numerous lymphoid
nodules, which form the most conspicuous histologic
feature of this organ. These lymphoid nodules show
germinal centers and are not confined to the lamina
propria, but penetrate the muscularis mucosae to
extend into the submucosa ( present often in the
submucosa).
Argentaffin and nonargentaffin endocrine cells are present in the base of mucosal glands just as
in the small intestine.

5. The submucosa has numerous blood vessels.
The connective tissue of the submucosa of appendix is
characterized by the abundance of fat cells.
The submucosa has abundant lymphoid tissue.
The muscularis externa (propria)of the appendix is thin
but has two layers of smooth muscle cells (inner
circular and outer longitudinal) as elsewhere in the
alimentary tract. Teniae coli are absent. The
parasympathetic ganglia of the myenteric plexus are
located between the inner and outer smooth muscle
layers of the muscularis externa.
Serosa forms the outermost coat of the appendix under
which are seen adipose cells .

7. Acute Appendicitis - Epidemiology
Acute inflammation of the appendix, acute appendicitis, is
the most common acute abdominal condition confronting the
surgeon.
The condition is seen more commonly in older children and young adults, and
is uncommon at the extremes
of age.
The disease is seen more frequently in the West and
in affluent societies which may be due to variation in diet—
a diet with low bulk or cellulose and high protein intake more
often causes appendicitis.

8. ETIOPATHOGENESIS
The most common mechanism is obstruction of the lumen
from various etiologic factors that leads to increased intraluminal pressure.
This presses upon the blood vessels to produce ischaemic injury
which in turn favours the bacterial proliferation and hence acute
appendicitis.
Acute appendicitis is thought to be initiated by progressive increases in intraluminal pressure
that compromises venous outflow. In 50% to 80% of cases, acute appendicitis is associated with
overt luminal obstruction, usually by a small, stonelike mass of stool, or fecalith, or, less
commonly, a gallstone, tumor, or mass of worms. Ischemic injury and stasis of luminal contents,
which favor bacterial proliferation, trigger inflammatory responses including tissue edema and
neutrophilic infiltration of the lumen, muscular wall, and periappendiceal soft tissues.

9. The common causes of appendicitis are as under:
A. Obstructive
1. Faecolith/ Fecalith
2. Calculi (Stones)
3. Foreign body
4. Tumour
5. Worms (especially Enterobius vermicularis)
6. Diffuse lymphoid hyperplasia, especially in children.
B. Non-obstructive
1. Haematogenous spread of generalised infection
2. Vascular occlusion
3. Inappropriate diet lacking roughage.

11. Phlegmon is a spreading diffuse inflammatory process with
formation of suppurative/purulentexudate or pus. This is the
result of acute purulent inflammation which may be related to
bacterial infection, however the term 'phlegmon' mostly refers
to a walled-off inflammatory mass without bacterial infection,
one that may be palpable on physical examination.
Aposteme:A swelling filled with purulent matter.

12. MORPHOLOGIC FEATURES
Grossly, the appearance depends upon the stage at which the
acutely-inflamed appendix is examined.
In early acute appendicitis, the organ is swollen and serosa
shows hyperaemia.
In welldeveloped acute inflammation called acute suppurative
appendicitis, the serosa is coated with fibrinopurulent
exudate and engorged vessels on the surface.
In further advanced cases called acute gangrenous appendicitis,
there is necrosis and ulcerations of mucosa which extend
through the wall so that the appendix becomes soft and
friable and the surface is coated with greenish-black
gangrenous necrosis.

13. Gross description
● Fibrinopurulent exudate on serosa, prominent
vessels
● Lumen may contain blood-tinged pus
● Variable perforation, mucosal ulceration, fecalith
or other obstructing agent
The inflammatory reaction transforms the normal glistening serosa into a dull, granular
appearing, erythematous surface.

15. Microscopy
Microscopically, the most important diagnostic
histological
criterion is the neutrophilic infiltration of the muscularis
propria.
Inearly stage, the other changes besides acute
inflammatory
changes, are congestion and oedema of the appendiceal
wall.
In later stages, the mucosa is sloughed off, the wall
becomes necrotic, the blood vessels may get thrombosed
and there may be neutrophilic abscesses in the wall.
Diagnosis of acute appendicitis requires neutrophilic infiltration of the muscularis propria.

16. Micro description
● Mucosal ulceration
● Minimal (if early) to dense neutrophils in
muscularis propria with necrosis, congestion,
perivascular neutrophilic infiltrate
● Late: absent mucosa, necrotic wall,
prominent fibrosis, granulation tissue, marked
chronic inflammatory infiltrate in wall,
thrombosed vessels

17. Acute appendicitis. Microscopic appearance showing diagnostic
neutrophilic infiltration into the muscularis propria. Other changes
present are necrosis of mucosa and periappendicitis.

19. CLINICAL COURSE
The patient presents with features of acute
abdomen as under:
1. Colicky pain, initially around umbilicus but later
localised to right iliac fossa
2. Nausea and vomiting
3. Pyrexia of mild grade
4. Abdominal tenderness
5. Increased pulse rate
6. Neutrophilic leucocytosis.

20. Clinical features
A classic physical finding is McBurney’s sign, deep
tenderness noted at a location two thirds of the
distance from the umbilicus to the right anterior
superior iliac spine (McBurney’s point).
Complications:
1. Peritonitis
2. Abscess
3. Adhesions
4. Portal Pylephlebitis
5. Mucocele

21. COMPLICATIONS
If the condition is not adequately managed, the following
complications may occur:
1. Peritonitis. A perforated appendix as occurs in
gangrenous appendicitis may cause localised or generalised
peritonitis.
2. Appendix abscess. This is due to rupture of an appendix
giving rise to localised abscess in the right iliac fossa. This
abscess may spread to other sites such as between the liver
and diaphragm (subphrenic abscess), into the pelvis between
the urinary bladder and rectum, and in the females may
involve uterus and fallopian tubes.

22. 3. Adhesions. Late complications of acute appendicitis are
fibrous adhesions to the greater omentum, small intestine
and other abdominal structures.
4. Portal pylephlebitis. Spread of infection into mesenteric
veins may produce septic phlebitis and liver abscess.
5. Mucocele. Distension of distal appendix by mucus
following recovery from an attack of acute appendicitis is
referred to as mucocele. It occurs generally due to proximal
obstruction but sometimes may be due to a benign or
malignant neoplasm in the appendix. An infected mucocele
may result in formation of empyema of the appendix.

23. TUMOURS OF APPENDIX
Tumours of the appendix are quite rare. These
include:
• Carcinoid tumour (the most common),
• Pseudomyxoma peritonei and
• Adenocarcinoma.
CARCINOID TUMOUR.
Both argentaffin and argyrophil types are
encountered, the former being more
common.
Appendiceal carcinoids, occur more frequently in 3rd and 4th decades of life without any sex
predilection, are often solitary and behave as locally malignant tumours.

24. Morphology
Grossly, carcinoid tumour of the appendix is
mostly situated near the tip of the organ and
appears as a circumscribed nodule, usually
less than 1 cm in diameter, involving the wall
but metastases are rare.
Histologically, carcinoid tumour of the appendix
resembles other carcinoids of the midgut.
Appendiceal carcinoids commonly involve the tip of the organ and are solitary

25. Tumors of Appendix
PSEUDOMYXOMA PERITONEI. Pseudomyxoma peritonei
is appearance of gelatinous mucinous material around the
appendix admixed with epithelial tumour cells. It is generally
due to mucinous collection from benign mucinous
cystadenoma of the ovary or mucin-secreting carcinoma of
the appendix.
ADENOCARCINOMA. It is an uncommon tumour in the
appendix and is morphologically similar to adenocarcinoma
elsewhere in the alimentary tract.

26. THANKS
Haveagoodday.