ABSTRACT
Excluding pain directly originating from the abdominal wall, which has somatic characteristics, abdominal pain in cancer is due predominantly to a visceral involvement. Visceral cancer pain originates from a primary or metastatic lesion involving the abdominal or pelvic viscera. Mechanic stimuli, such as torsion or traction of mesentery, distension of hollow organs, stretch of serosal and mucosal surfaces, and compression of some organs produce pain in humans (1). These conditions are frequently observed in cancer patients with an abdominal diseases and intraperitoneal masses. Human studies have revealed that pain is produced when the intraluminal pressure of hollow organs is maintained above certain pressure thresholds. Obstruction or inflammation within the biliary tract or pancreatic duct induces pain directly related to an increased intraluminal pressure with consequent inflammation, and release of pain-producing substances (2). Distension or traction on the gallbladder leads to deep, epigastric pain, inspiratory distress, and vomiting. Spontaneous spasm of the sphincter of Oddi or that induced by morphine leads to increases in pain sensation, resulting in a paradoxical opioid-induced pain. On the other hand, morphine and other opioids increase the pressure threshold necessary to produce the sensation of pain due to distension of the biliary system. Renal colic is commonly secondary to ureteral obstruction and subsequent distension of ureter and renal pelvis. This may be evident in circumstances in which an abdominal-pelvic mass compresses or invades ureters, as often occurs in gynecological cancers.
