Nitrergic hyperinnervation in appendicitis and in appendices histologically classified as normal

Area of Science:

• Gastroenterology
• Neuroscience
• Pathology

Background:

• The exact causes of appendicitis are not fully understood.
• Histologically normal appendices are often removed during surgery for suspected appendicitis.
• The enteric nervous system plays a role in gastrointestinal immune and inflammatory responses.

Purpose of the Study:

• To examine the nitrergic innervation of inflamed appendices, histologically normal appendices from appendicitis patients, and normal control appendices.
• To utilize whole-mount preparation techniques for detailed analysis.

Main Methods:

• Collected full-thickness appendix specimens from 28 inflamed, 31 histologically normal (suspected appendicitis), and 23 normal control appendices.
• Performed nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry and neuronal nitric oxide synthase immunohistochemistry.
• Quantified myenteric plexus density using a computerized analysis system.

Main Results:

• Myenteric plexus density in normal appendices decreased after age 3.
• Appendices from patients over 4 years showed smaller ganglia and thinner nerve bundles compared to the large bowel.
• Neuronal hypertrophy was observed in 55% of inflamed and 41% of histologically normal appendices, with thicker nerve bundles and more ganglion cells.

Conclusions:

• Altered myenteric plexus architecture in patients over 3 suggests changes in appendix function and motility early in life.
• Increased neuronal components in a significant proportion of appendices suggest an underlying chronic abnormality, not just acute inflammation.
• This chronic abnormality may result from chronic obstruction or repeated inflammatory episodes in histologically normal appendices.