Appendicitis

Author: Mikael Häggström
Appendicitis may histopathologically be defined as neutrophilic infiltrates of the wall of the appendix in the correct clinical context.

  See also: General notes on fixation

Comprehensiveness

On this resource, the following formatting is used for comprehensiveness:

• Minimal depth
• (Moderate depth)
• ((Comprehensive))

Gross processing

Standard sections if the appendix appears inflamed and there are no signs of malignancy. Describe abnormal signs including:

• 

  Appendicitis with congestion

• 

  Serosa with a patchy purulent exudate.

• 

  Appendicitis, with the lumen containing a blood-tinged purulent exudate.

• 

  Longitudinal section showing a red inflamed mucosa with an irregular luminal surface (in a case of acute suppurative appendicitis).

Further information: Appendix

Microscopic evaluation

• Evaluate depth of the inflammation.
• Look for any perforation of the wall.
• Look for cancerous cells (which may have caused the appendicitis). Further information: Appendix
• (Attempt to specify the type of appendicitis as either of the following:)

Types

Classification of acute appendicitis based on gross pathology and light microscopy characteristics

Pattern	Gross pathology	Light microscopy	Image	Clinical significance
Acute intraluminal inflammation	None visible	Only neutrophils in lumen No ulceration or transmural inflammation		Probably none
Acute mucosal inflammation	None visible	Neutrophils within mucosa, and possibly in submucosa Mucosal ulceration		May be secondary to enteritis.
Suppurative acute appendicitis	May be inapparent. Dull mucosa Congestion of surface vessels Fibropurulent serosal exudate in late cases Dilation of the appendix	Neutrophils in mucosa, submucosa and muscularis propria, potentially transmural. Extensive inflammation Commonly intramural abscesses Possibly vascular thrombosis		Can be presumed to be primary cause of symptoms
Gangrenous/necrotizing appendicitis	Friable wall Purple, green or black color	Transmural inflammation, obliterating normal histological structures Necrotic areas Extensive mucosal ulceration		Will perforate if untreated
Periappendicitis	May be inapparent. Serosa may be congested, dull and exudative	Serosal and subserosal inflammation, no further than outer muscularis propria to be called isolated.		If isolated, probably secondary to other disease
Eosinophilic appendicitis	None visible	>10 eosinophils/mm2 in muscularis propria. No changes conforming to other types of appendicitis		Possibly parasitic, or eosinophilic enteritis.
Chronic appendicitis	Fibrosis	Predominantly mononuclear infiltrate rather than neutrophilic.		Should preferably correlate with long-term or recurrent symptoms.

Further workup

(In acute suppurative appendicitis, still look for any periappendicitis. Also look by the lumen for parasites.)

Microscopy report

Should include, if detected:

• Acute or chronic appendicitis
• Depth of inflammation
• Any abscess and\or perforation
• Necrosis and\or ulceration, at least if transmural

(Classification into one or several types as per table above.)

Example

(Appendix, resection (or appendectomy):) Acute appendicitis and periappendicitis with transmural necrosis and perforation.

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