Visceral pain Flashcards
Nociception in viscera
- afferent nerves that run parallel wtih efferent autonomic nerves
- Unmyelinated C fibres mainly
- larger nerves within which visceral afferents run:
- vagus
- pelvis nerves
- spinal nerves
Pathophysiology
- cell bodies of sensory fibres from abdominal viscera
- celiac plexus (anterior to crura of diaphram and L1)
- hypogastric plexus
- Superior (L5)
- Inferior (sacrococcygeal junction)
- carry visceral info from pelvis and left colong
- sacral plexus
- impulses proceed to dorsal horn of TL spinal cord
Differences between anatomy of visceral nociceptive and somatosensory system
- innervation density MUCH lower for visceral nerves
- Visceral sensory nerves project to larger number of levels in spinal cord
- visceral nerves project to contralateral side
- one visceral sensory neuron may innervate two different visceral organs
Visceral nociceptors types
- respond to distention, ischemia, electical stimulation
- Mechanosensory receptors:
- distention
- located in walls and muscles of organs
- Chemoreceptors
- mucosa and muscles
- Thermoreceptors
- mucosa and muscles
Peripheral activation of visceral pain
- distention, inflammation, torsion, ischemia
- also chemicals like bradykinin, acidemia
- Cardiac ischemia:
- drop in pH –> lactate
- acid sensing ion channel and TRPV channels activated
- Gut:
- mechanosensory receptors TRPV, sodium channels
- cytokines, substance P, etc
- Pancreatic cancer:
- inflammatory perineural invasion by pancreatic cancer cells –> aroborization of sensory nerves
Peripheral sensitization in visceral pain
- changes in functioning of a primary afferent nerve that may include
- reduced threshold
- spontaneous activation
- increased response
- sensitized by inflammatory or adrenergic compounds
- lasts after exposure
- bradykinin, cytokines
- visceral hyperalgesia
Central sensitization. in visceral pain
- amplification of neural signalling in CNS
- allodynia, hyperpathia, hyperalgesia
- ? NMDA receptor
Clinical aspects of visceral pain
- Hollow viscus:
- poorly localized
- vague, gnawing, crampy
- Solid organs, capsules
- better localized
- sharp
- stabbing
- all can have autonomic sx (nausea)
- aversive emotional reactions
Referred pain
Viscerosomatic referred pain
- visceral and somatic afferent fibres converge on same lamina of spinal cord
- cortex may interpret signals as emanating from corresponding somatic site
Viscero-visceral referred pain/ cross organ sensitivity
- shared afferents for 2 different organs
- CAD and biliary tree common afferent T5
- intestive and pelvic organs common afferent T10-L1
Patterns of visceral referral pain
- Thoracic region pain
- referred from cardiac or esophagus
- lung and diaphragm refers to shoulder
- Upper abdominal wall pain
- upper abdo organs (pancreas, stomach, liver)
- liver, porta hepatis : RUQ and refers to shoulder
- Pain in lower abdominal wall
* colon, bladder, uterus, kidney
Referred pain syndrome : cervical distention
- pain in lower abdo and back
Referred pain from bladder distention
- subprapubic
Referred pain from thoracic injuries (cardiac, esophageal, lung)
- Thoracic pain
- Cardiac : L arm
- lung –> shoulder
Referred pain from upper abdominal organs
- Upper abdo wall
- thoracic back
Referred pain from abdominopelvic organs
- lower abdominal wall
Referred pain from porta hepatis
- pain in ipsilateral scapula
Referred pain to diaphragm
- pain to ipsilateral shoulder
Pain from pancreatic cancer
- inflammatory perineural invasion by pancreatic cancer cells
- boring, well localized upper abdo pain radiates to back
Visceral pain treatment principles
- Opioids
- adjuvants for smooth muscle
- NSAIDS
- buscopan
- oxybutynin
- interventional approaches (blocks, stents)
