problems. as a result of this study there has been a further research into the elimination of referred pain through certain body movements. one example of this is referred pain in the calf. mckenzie showed that the referred pain would move closer to the spine when the patient bent backwards in full extension a few times. more importantly, the referred pain would dissipate even after the movements were stopped. general diagnosis as with myocardial ischaemia, referred pain in a certain portion of the body can lead to a diagnosis of the correct local center. somatic mapping of referred pain and the corresponding local centers has led to various topographic maps being produced to aid in pinpointing the location of pain based on the referred areas. for example, local pain stimulated in the esophagus is capable of producing referred pain in the upper abdomen, the oblique muscles, and the throat. local pain in the prostate can radiate referred pain to the abdomen, lower back, and calf muscles. kidney stones can cause visceral pain in the ureter as the stone is slowly passed into the excretory system. this can cause immense referred pain in the lower abdominal wall. further, recent research has found that ketamine, a sedative, is capable of blocking referred pain. the study was conducted on patients with fibromyalgia, a disease characterized by joint and muscle pain and fatigue. these patients were looked at specifically due to their increased sensitivity to nociceptive stimuli. furthermore, referred pain appears in a different pattern in fibromyalgic patients than non-fibromyalgic patients. often this difference manifests as a difference in terms of the area that the referred pain is found (distal vs. proximal) as compared to the local pain. the area is also much more exaggerated owing to the increased sensitivity.