Screening for surreptitious laxative abuse

Abstract

Purgative use, along with blood-letting, has been a mainstay of medical therapy for the last two millennia. Nowadays, prescription laxatives are usually reserved for treating severe constipation or as a bowel washout. However, over-thecounter laxatives are freely available and sold in huge quantities. Chronic laxative use is undoubtedly common and, if excessive, may cause symptoms, the most common being diarrhoea, abdominal pain, general weakness, weight loss, nausea and vomiting. The only sign suggestive of chronic laxative abuse is melanosis coli, a rectal pigmentation that is associated with longterm ingestion of anthraquinone laxatives. Factitious diarrhoea due to surreptitious laxative abuse (SLA) with phenolphthalein was initially detected fortuitously during alkalinization of faecal fat for analysis. Since then, it has been increasingly recognized as an important medical and diagnostic problem. However, the diagnosis may often be overlooked, resulting in extensive investigations. These investigations are often normal, leading to an erroneous diagnosis of irritable bowel syndrome or, since chronic laxative ingestion may cause mucosal in ammation, in ammatory bowel disease. Such patients may have a form of Munchausen’s syndrome and are often women with emotional, psychiatric or social dif®culties, who are otherwise healthy. A variant of SLA known as Munchausen syndrome by proxy or Polle syndrome has been reported in several young children whose diarrhoea was caused deliberately by a parent. Various reports have estimated the prevalence of SLA to be between 4% and 26% of patients with chronic diarrhoea (Table 1). This variation probably re ects differences in patient selection and the poor sensitivity of some detection methods. There are no data on the prevalence of laxative abuse by proxy, although (judging from the few case reports) it appears to be very rare. However, the fact that three of these cases were reported from a single centre in which phenolphthalein was the only laxative screened suggests that the prevalence may be underestimated. In addition, only 50% of children’s hospitals in the UK generate laxative screening requests. Laxatives are quite widely abused, both to control body weight and by patients with eating disorders. In one review of 31 reports of patients with bulimia, the combined prevalence of laxative use was about 15%. However, in this group the abuse is not usually secretive and is unlikely to raise medical or diagnostic issues.