‘Referred’ pain is pain perceived at a location other than the site where a painful stimulus actually acts. The gallstone disease, hepatic cancer and/or abscess, peritoneal diseases, some iatrogenic situations (laparoscopy, hepatic biopsy, radiofrequency hepatic ablation), spleen traumas and adrenal metastases are the most relevant visceral causes of referred shoulder pain. Hepatic infectious or neoplastic processes as well as biliary colic are often accompanied by pain at neck, shoulder, scapula, clavicle and upper arm [1]. In all these cases, pain is related to normal anatomical features of diaphragm innervation [2], as well explained in several historic scientific articles:

The diaphragm will suffer more or less by contact with the inflamed organ and through the irritation carried to it along the phrenic twigs of the liver; and so the influence may pass up the trunk of the phrenic nerve to the brachial, and even the cervical plexus, and thus the subclavius nerve and others may be affected, which may account for pain about the clavicle, and partly for that in the side of the neck and even in the arm [3].

In this contest, filaments of the phrenic nerve penetrate the diaphragm and communicate with the ganglia that lie around the coeliac artery; other filaments are distributed to the muscles about the shoulder, and in this way has been explained the fact that disease or irritation of the liver is very apt to be accompanied with pain in the shoulder [4].

Right shoulder pain may be a symptom of the gallstones passage in association to epigastric and right hypochondrial pain, either in absence of heartburn or independent from severity of visceral involvement [5, 6]. During biliary colic specific laboratory parameters change, all serum bilirubin, alkaline phosphatise, γ-glutamil transpeptidase and, sometimes, both aminotransferases increase. The gold instrumental standard for diagnosis of gallbladder and biliary tract lithiasis is ultrasonography.

Indeed, when associated to respiratory movements and progressive clinical deterioration (weight loss and fever), right shoulder pain may be a satellite of hepatic cancer or abscess [7].

Moreover, laparoscopic surgery (cholecystectomy in particular) often causes right shoulder scapular pain during post-operative period, accompanied by nausea, vomit and abdominal pain. Probably due to residual pneumoperitoneum, the mechanism that exactly determines this pain in not yet clear [8]: it may be caused by neck and shoulder irradiation of diaphragm irritation from CO₂ peritoneal conversion to carbonic acid (H₂CO₃) [9].