Co-existing algogenic conditions in two internal organs in the same patient may mutually enhance pain symptoms (viscero-visceral hyperalgesia). The present study assessed this phenomenon in different models of visceral interaction. In a prospective evaluation, patients with: (a) coronary artery disease (CAD)+gallstone (Gs) (common sensory projection: T5); (b) irritable bowel syndrome (IBS)+dysmenorrhea (Dys) (T10-L1); (c) dysmenorrhea/endometriosis+urinary calculosis (Cal)(T10-L1); and (d) gallstone+left urinary calculosis (Gs+LCal) (unknown common projection) were compared with patients with CAD, Gs, IBS, Dys or Cal only, for spontaneous symptoms (number/intensity of pain episodes) over comparable time periods and for referred symptoms (muscle hyperalgesia; pressure/electrical pain thresholds) from each visceral location. In patients' subgroups, symptoms were also re-assessed after treatment of each condition or after no treatment. (a) CAD+Gs presented more numerous/intense angina/biliary episodes and more referred muscle chest/abdominal hyperalgesia than CAD or Gs; cardiac revascularization or cholecystectomy also reduced biliary or cardiac symptoms, respectively (0.001<p<0.05). (b) IBS+Dys had more intestinal/menstrual pain and abdomino/pelvic muscle hyperalgesia than IBS or Dys; hormonal dysmenorrhea treatment also reduced IBS symptoms; IBS dietary treatment also improved dysmenorrhea (0.001<p<0.05) while no treatment of either conditions resulted in no improvement in time of symptoms from both. (c) Cal+Dys had more urinary/menstrual pain and referred lumbar/abdominal hyperalgesia than Cal or Dys; hormonal dysmenorrhea treatment/laser treatment for endometriosis also improved urinary symptoms; lithotripsy for urinary stone also reduced menstrual symptoms (0.001<p<0.05). (d) In Gs+LCal, cholecystectomy or urinary lithotripsy did not improve urinary or biliary symptoms, respectively. Mechanisms of viscero-visceral hyperalgesia between organs with documented partially common sensory projection probably involve sensitization of viscero-viscero-somatic convergent neurons.
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