8.3 Acute Abdominal Pain

Question 1

When damaged does the parietal peritoneum produce visceral or somatic pain?

Question 2

Describe the felt sense of visceral vs somatic pain

Answer 2

• Visceral: dull, aching, squeezing, hard to localise
• Somatic: sharp, easy to localise

Question 3

Which type of fibres detect visceral vs somatic pain? Which are myelinated/unmyelinated?

Answer 3

• Visceral: unmyelinated C fibres
• Somatic: myelinated a delta fibres

Question 4

Explain the mech of referred pain

Answer 4

• Somatic pain synapses in the dorsal horn at the same spinal level as other afferent visceral fibres
• Brain interprets visceral pain as somatic

Question 5

Characteristics/distribution of pancreatitis pain. Does it radiate? Why?

Answer 5

• Dull epigastric pain (sharper in response to sudden damage; inflammation can irritate the parietal peritoneum)
• Can radiate to back (referred pain from somatic fibres of the back)

Question 6

Why does appendicitis pain shift and change in character over time?

Answer 6

• Over time, RIF parietal peritoneum becomes irritated by inflammation
• This causes a shift from dull, squeezing, poorly localised visceral pain to sharper somatic pain

Question 7

Characteristics/distribution of pancreatitis pain.

Answer 7

• Dull, burning retrosternal pain
• Visceral, since internal GI structure (oesophagus)
• Burning nature due to acidic contents of reflux

Question 8

Voluntary vs involuntary guarding of the abdomen

Answer 8

Voluntary: patient tenses muscles in anticipation of pain

Involuntary: patient tenses muscles automatically in response to real pain

Question 9

Mechanism of rebound tenderness

Answer 9

• Irritated peritoneum
• Removing taking force off the abdomen causes sudden change in peritoneal pressure, aggravating the inflamed peritoneum

Question 10

Mechanism(s) of Rovsing’s sign (cross tenderness)

Answer 10

• Likely due to shared innervation
• Could also be change in pressure, or movement of peritoneum