Bulimia Nervosa

A psychiatric disorder characterised by recurrent episodes of binge eating: consumption of an objectively large amount of food within a discrete period, with a subjective sense of loss of control over eating.

Binges are followed by recurrent inappropriate compensatory behaviour to prevent weight gain: self induced vomiting, laxative or diuretic misuse, excessive exercise, or fasting. The behaviours occur at least weekly over a sustained period.

Body weight is typically within or above the normal range. This distinguishes the presentation from the significantly low body weight typical of anorexia nervosa.

However, the underlying psychopathology of disturbed body image and overvaluation of weight and shape in self evaluation overlaps substantially between the two conditions.

Pathophysiology

• Binge eating is believed to reflect a complex interaction of restrictive dietary intent (frequently present between binges), physiological hunger, and psychological factors. These include mood regulation and loss of normal inhibitory control over eating.
• Compensatory behaviour is driven by the significant shame and fear of weight gain that follow a binge.
• Self induced vomiting is the most common compensatory behaviour. It produces a characteristic pattern of medical complications.
• Direct mechanical and chemical effects of repeated vomiting include dental erosion from gastric acid exposure and oesophageal irritation. In severe or forceful cases there is a risk of oesophageal tear or, rarely, rupture.
• Calloused skin over the dorsum of the hand, from repeated contact with the teeth during self induced gagging, is termed Russell sign.
• Electrolyte and acid base disturbance results from loss of hydrochloric acid rich gastric contents: hypokalaemia and metabolic alkalosis.
• This contrasts with the metabolic acidosis more typically associated with laxative misuse, because the site and mechanism of fluid loss differ.

• Recurrent binge eating episodes, typically conducted in secrecy because of shame, followed by compensatory behaviour, are the core defining behavioural pattern.
• Body weight is typically normal or above normal, so the diagnosis is frequently not suspected from physical appearance alone. This contributes to a recognised pattern of diagnostic delay compared with the more visibly apparent anorexia nervosa.
• Dental erosion, particularly of the palatal surfaces of the upper teeth, results from their direct exposure to refluxed gastric acid during vomiting.
• Parotid gland swelling (sialadenosis) is a benign but cosmetically apparent glandular hypertrophy associated with recurrent vomiting. Both signs can be diagnostically revealing.
• Symptoms and signs of electrolyte disturbance include muscle weakness and cardiac arrhythmia risk from significant hypokalaemia. In severe or longstanding cases, renal impairment may occur. These complications need active assessment.
• Significant psychological distress, shame and secrecy surround the binge purge pattern. Depression, anxiety, and impulsive behaviour in other domains frequently coexist.
• As in anorexia nervosa, there is a significant associated suicide risk that warrants explicit assessment.

• Diagnosis rests on a detailed clinical history. This explores the pattern, frequency and duration of binge eating and compensatory behaviour, and the associated cognitions regarding weight and shape. The general principles for eating disorders apply.
• Direct, sensitive enquiry about specific compensatory behaviours is essential, given the frequent secrecy and shame.
• Full electrolyte assessment is an important component of medical evaluation. Check potassium, and bicarbonate given the characteristic metabolic alkalosis with vomiting related purging.
• Dental assessment and examination for parotid swelling are also part of the evaluation.
• Electrocardiography is appropriate where significant electrolyte disturbance is identified or suspected, given the arrhythmia risk.
• Assess for the broader medical complications and apply the risk stratification approach used for eating disorders generally.
• In bulimia nervosa, medical risk relates predominantly to the electrolyte and structural consequences of purging. Body weight is typically normal or near normal, so the malnutrition related complications more characteristic of anorexia nervosa are less prominent.

• Cognitive behavioural therapy adapted for eating disorders is the first line, most strongly evidence supported psychological treatment. It addresses cognitive distortions regarding weight, shape and eating, and the pattern of binge eating and compensatory behaviour. It is typically delivered over a structured course of approximately twenty sessions.
• Fluoxetine at a higher dose than typically used for depression (commonly 60 mg once daily) has established evidence of efficacy in reducing binge eating and purging frequency.
• It is a useful adjunctive or alternative option, particularly where access to psychological therapy is limited or a coexisting depressive disorder warrants pharmacological treatment in its own right.
• Nutritional counselling supports regular, structured eating patterns. Periods of restriction between binges frequently perpetuate the binge urge. Counselling works to break the restrict-binge-purge cycle central to maintenance of the condition.
• Correct any significant electrolyte disturbance according to standard principles.
• Dental review and preventive dental care are important, given the risk of progressive dental erosion with ongoing vomiting.
• Body weight is typically normal, and severity may be less visually apparent than in anorexia nervosa. Careful, non-judgmental assessment supports timely diagnosis and access to specific evidence based treatment.
• Keep a low threshold for enquiry about binge eating and compensatory behaviour in any patient with relevant physical signs (dental erosion, electrolyte disturbance, parotid swelling) or psychological features.
• Overall prognosis is generally more favourable than for anorexia nervosa, particularly with prompt access to cognitive behavioural treatment.