Symptom scores, serotonin and 5-hydroxyindole acetic acid levels in cancer patients with and without bowel obstruction.

Some 40% of patients with advanced ovarian cancer, and 10% of patients with colon cancer, experience bowel obstruction as a complication of disease. Animal studies have shown that both increased luminal pressure, and ischaemic injury, evoke measurable increases in serotonin (5HT) from small bowel mucosa. These reports suggest that both the pressure and ischaemic consequences of malignant bowel obstruction (particularly small bowel) could cause release of 5HT in humans. Released 5HT binds to terminal vagal afferents triggering nausea, before being metabolised in the liver to 5-hydroxyindole acetic acid (5-HIAA), an established mechanism in chemotherapy-induced emesis. Two previous studies have examined 5HT in bowel obstruction. In 40 patients with non-malignant bowel obstruction, elevated plasma 5HT was found in acute mechanical obstruction, but not in paralytic ileus or chronic obstruction. The second study (published abstract) found elevated urinary 5HT in 13 patients with obstruction compared with 15 patients without, all of whom had ovarian cancer. We wanted to examine symptom scores and serotonin in patients with malignant bowel obstruction. Our hypotheses were that patients with malignant bowel obstruction would have more severe symptom scores compared with non-obstructed groups, and that symptom scores would correlate with levels of 5HT and 5-HIAA.