Management of eating disorders is a key skill for liaison psychiatrists, and patients with eating disorders frequently present in general hospital settings. They can complicate severe and enduring conditions, such as diabetes, with subsequent high mortality and morbidity. The role of the liaison psychiatrist is often in diagnosis, risk management and early intervention. However, this role has been broadened by increasing demands to support bariatric surgery services, as well as by addressing body image disorders such as muscle dysmorphia that overlap with anorexia nervosa and bulimia nervosa. Liaison psychiatry services can benefit from awareness of these demands if the nettle is grasped, but risk being stung if services are not adequately commissioned.

Diagnosis and classification

Eating disorders, including anorexia nervosa, bulimia nervosa and binge eating disorder, are common. Anorexia nervosa carries one of the highest standardised mortality rates of any psychiatric disorder. Physical complications are widespread, affecting all organ systems, and physical presentations in a variety of medical settings are frequent.

Although not classified as an eating disorder, the assessment and management of some cases of morbid obesity shares commonality with eating disorder expertise. Current nosology of eating disorders therefore does not necessarily reflect the range of weight and eating-related problems likely to be faced by the liaison psychiatrist. Furthermore, overlap between body image disorders, including body dysmorphia and disordered eating, can generate diagnostic confusion. This is particularly exemplified in a newly characterised condition, muscle dysmorphia, lying within a nosological hinterland between body dysmorphia and eating disorders, such that some commentators (Morgan, 2000) have argued it is a variant of an eating disorder. This chapter will explore practical aspects of these issues within the existing literature.

DSM-IV (American Psychiatric Association, 1994) diagnostic criteria form a better framework for diagnosis of eating disorders than ICD-10 (World Health Organization, 1992), with greater clarity of operational definitions. However, DSM-IV itself fails to address the transdiagnostic nature of eating disorders, in which patients flit between different diagnostic categories with the same core psychopathology, and it is likely to be revised in future classifications. The heterogeneous category of eating disorder not otherwise specified (EDNOS) is particularly useful to liaison psychiatrists, who may well be called upon to treat patients not meeting full threshold for anorexia or bulimia nervosa, yet still pose a challenge in a medical setting. This is particularly true for EDNOS in diabetes and pregnancy.