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Bulimia nervosa

Definition
  • Disease characterised by:
    • recurrent episodes of binge eating
    • behaviours aimed at compensating for the binge
  • Binge-eating episodes are characterised by:
    • eating an amount of food that is definitely larger than most people would eat
      • at least twice the normal amount of food ingested
    • over a discrete period of time
      • it must be ingested more quickly than normally
  • Binges are accompanied by a sense of lack of control over eating during the episode
  • Recurrent inappropriate compensatory behaviours occur in order to prevent weight gain
    • Self-induced vomiting
    • Fasting
    • Excessive exercise
    • Misuse of laxatives, diuretics, enemas, or other medication
  • Binge-eating episodes typically occur, on average, at least twice-weekly for 3 months
Risk Factors
  • Female sex
    • 90% of patients are female
  • Personality disorder
    • Association reported between negative emotionality, perfectionism, drive for thinness, poor interoceptive (body stimuli) awareness, a perception of ineffectiveness in one's life, and obsessive-compulsive personality traits.
    • OCD predicts a poorer outcome if it is not treated
    • Histrionic personality traits and self-directedness predict a more favourable course and/or outcome
  • Body-image dissatisfaction
    • Common in those with bulimia nervosa, as well as in the mothers of people with bulimia
    • Body-image dissatisfaction is often reduced after improvement in bulimia nervosa
  • Hx of sexual abuse
    • Sexual abuse before puberty can cause severe body image dissatisfaction and increase the risk of bulimia nervosa
    • However, about one third of women have a history of sexual abuse
  • Impulsivity
    • Impulsivity and self-injurious behaviour are increased in bulimia nervosa according to cross-sectional studies
    • Cause and effect are unclear
  • FHx alcoholism
    • Alcoholism is more common in the family history of those with bulimia nervosa than in those with anorexia nervosa
    • Alcoholism may be a marker for other psychiatric or social abnormalities
  • FHx depression
    • Depressive symptomatology is common in bulimia nervosa
    • Major depressive disorder can worsen the course of bulimia
  • FHx eating disorder
    • Excessive concern about weight and shape is common in such families
  • Childhood overweight or obesity
    • Being obese or overweight in childhood increases the risk of bulimia nervosa
  • Exposure to media pressure
    • Idealisation of body shape and eating has a strong effect on the development of bulimia nervosa
  • Early onset of puberty
    • Early onset of puberty is associated with early onset of bulimia nervosa
  • Urbanisation
    • Bulimia nervosa is more common in urban areas, as are schizophrenia and depression
    • By contrast, prevalence of anorexia nervosa is no different in rural and urban areas
    • Bulimia is highly related to societal and cultural pressures
    • Anorexia is more likely to depend on specific genetic predisposition and triggered by weight loss
  • FHx obesity
    • Weak predictor of bulimia.
Differential diagnosis
Epidemiology
  • Prevalence varies worldwide
    • For example, lifetime prevalence in women in Australia is 2.9%
    • Lifetime prevalence estimates of DSM-IV-defined bulimia nervosa in the US are 1.5% in women and 0.5% in men
  • Higher lifetime prevalence has been found in white women than in black women
  • This range of prevalence may reflect imperfect case-finding or differences in populations
Aetiology
  • The aetiology of bulimia nervosa is uncertain
  • A biopsychosocial theory of causation posits a combination of coexisting biological (genetic abnormalities in receptors or neurotransmitters), psychological, and social factors
  • Risk factors that are strongly associated with bulimia nervosa include:
    • female sex
    • perfectionism
    • body dissatisfaction
    • impulsivity
    • history of sexual abuse
    • family history of alcoholism, depression, or eating disorder
    • past obesity
    • exposure to media pressure
  • An association with urbanisation has been reported
  • Family history of obesity is considered a weak predictor of bulimia
  • Early onset of puberty is associated with early onset of bulimia nervosa
Clinical features
  • Recurrent episodes of binge eating
    • Necessary for diagnosis.
    • Binge eating must:
      • occur within a discrete period of time (e.g., 2 hours)
      • involve an amount of food that is definitely larger than most people would eat during a similar period of time and under similar circumstances
    • A sense of lack of control must be present during the episode
      • e.g., a feeling that one cannot stop eating or control what or how much one is eating
    • Occurs, on average, at least twice a week for 3 months
  • Recurrent inappropriate compensatory behaviour
    • There must always be some form of compensatory behaviour to attempt to burn off calories
    • This may be:
      • purging (vomiting, laxatives, enemas, suppositories)
      • non-purging (exercise, fasting).
    • Occurs, on average, at least twice a week for 3 months
  • Eating disturbance not exclusively during periods of anorexia nervosa
    • Confirmation of an eating disturbance that does not occur during periods of anorexia nervosa is a diagnostic requirement in DSM-IV
  • Depression and low self-esteem
    • Patients usually have low self-esteem, lack of confidence, and depressive thoughts
    • Treatment of concurrent depression improves outcome
    • Concurrent depression may be related to drug or alcohol abuse
    • Should be monitored and addressed in treatment
  • Concern about weight and body shape
    • Nearly always present, although it may be denied initially
    • Self-evaluation is unduly influenced by body shape and weight
  • Dental erosion
    • Erosion of adult teeth is permanent and can be extremely costly to correct
    • Dental changes often reduce self-esteem and can make it painful and difficult to chew hot or cold food.
    • It is important to prevent and treat dental erosion.
    • Better appearance is also a motivational tool.
    • Focusing on the changes in gums and teeth that point to a progression of tooth loss can motivate patients to accept treatment
  • Parotid hypertrophy
    • The parotid glands are bilaterally enlarged but are usually not tender unless the purging is frequent
  • Russell's sign
    • Scarring over the dorsum of the hands.
    • This results from pressing fingers against the teeth inserted into the mouth to induce vomiting
  • Arrhythmia 
    • More common in presence of hypokalaemia or hypomagnesaemia.
    • Loss of consciousness, fainting, ventricular arrhythmias, and arrhythmias lasting more than a few minutes are rare.
  • Menstrual irregularity
    • Occasional missed or abnormal menstrual periods can occur.
    • Important for counselling, particularly because contraceptive pills may be purged.
    • A skipped period may be due to pregnancy or to the bulimia itself
    • This contrasts with anorexia nervosa, where menstrual irregularity is a required component of the disease
  • Drug-seeking behaviour
    • Physicians should be aware that abuse of laxatives and drug-seeking behaviour for laxatives and appetite suppressants is common.
    • In addition, medications may be collected to use for suicide
  • Deliberate misuse of insulin
    • Patients with diabetes may skip insulin to control their weight.
    • This leads to marked fluctuations in blood sugar and rapid onset of diabetic microvascular complications
  • Self-injurious behaviour 
    • Patients will usually not mention such behaviour.
      • Therefore, their skin should be examined
  • GI symptoms
    • Oesophageal reflux, diarrhoea, constipation, and abdominal pain are frequent in bulimia nervosa.
    • These result from volume depletion and deficiencies of vitamins and minerals arising from bingeing on large volumes of food, with erratic eating in between vomiting
  • Hx of dieting
    • Patients with bulimia nervosa are often ashamed to admit they have the disease.
      • Therefore, a high index of suspicion is important.
    • A history of dieting would raise suspicion for the condition
  • Marked fluctuations in weight
    • A history of dieting along with a high index of suspicion would raise the possibility of the condition
  • Needle marks on skin
    • Patients may self-phlebotomise as a form of purging, but rarely give this history.
    • Anaemia and the presence of needle marks may be the only clues
Pathophysiology
  • The pathophysiology of bulimia nervosa is unknown
  • However, evidence suggests that people may binge and purge when:
    • they have low self-esteem
    • when they are pressured to conform to eating or to adhere to a specific weight and shape
    • when they are knowledgeable about bingeing and purging
  • Compensatory behaviours such as vomiting, use of laxatives, or exercise may result in large fluctuations in weight that reinforce the behaviour
    • These behaviours can result in:
      • erosion of the teeth
      • parotid and submandibular gland hypertrophy
      • oesophageal reflux, dysmotility, or spasm
      • gastric dysmotility
      • bowel irregularity
      • volume depletion
      • cardiac arrhythmia
      • metabolic abnormalities such as hypokalaemia or hypomagnesaemia
Investigations
  • Serum electrolytes
    • Hypokalaemia may be accompanied by other electrolyte disorders for which there are no ready explanations.
    • Elevated serum bicarbonate in bulimia nervosa usually indicates an alkalosis due to emesis of gastric acid
    • Electrolytes must be combined with ABG measurement to definitively diagnose an acid-base abnormality
  • Serum creatinine
    • May reflect azotaemia due to volume depletion
  • Serum magnesium
    • Total body magnesium depletion frequently occurs with normal serum magnesium levels
    • If serum magnesium is low, the total body levels are always low.
    • Serum magnesium should be ordered separately from serum electrolytes
  • Urine pregnancy test
    • The possibility of pregnancy should always be considered with a change in symptoms
  • Serum LFTs
    • Drug overdose, alcohol ingestion, or excess exercise may elevate aminotransferases
  • Serum creatine kinase
    • Drug overdose, alcohol ingestion, or excess exercise may elevate CK
  • FBC
    • Patients may self-phlebotomise as a form of purging, but rarely give this history.
    • Anaemia and the presence of needle marks may be the only clues
  • Urinalysis
    • Patients with comorbid diabetes mellitus may have poor glycaemic control.
    • Some patients may skip insulin to control their weight
  • ECG
    • If there is a deficiency of potassium or magnesium, or a history of anorexia nervosa, there can be a prolonged QTc interval or arrhythmias
    • If the QTc is >440 milliseconds, or rhythm or conduction is abnormal, urgent evaluation is required.
  • Serum ferritin
    • To evaluate presenting symptoms such as menstrual irregularity or abdominal symptoms
    • Ferritin may be low, reflecting low iron levels.
  • Serum B12
    • Nutritional deficiencies including B12 (or, rarely, thiamine, niacin, copper, and riboflavin) may be present
    • Bulimia should be considered in a young woman who presents with such a deficiency.
  • Serum RBC folate
    • May be seen in nutritional folate deficiency.
  • DEXA scan for bone density
    • Commonly normal unless there is a prior history of anorexia nervosa.
      • Bone density is often decreased in anorexia nervosa.
    • Low bone density correlates with low total body fat and amenorrhoea, neither of which is common in bulimia nervosa.
Management

a) conservative
  • cognitive behavioural therapy (CBT)
  • nutritional and meal support
  • other types of supportive psychological therapy
b) medical
  • glycaemic control
  • SSRI or serotonin-norepinephrine reuptake inhibitor (SNRI)
c) surgical
  • n/a
Prognosis
  • Bulimia nervosa has an average onset at an age of about 18 years
    • However bingeing and purging to a lesser degree is much more common
  • Many, if not most patients, who meet the diagnostic criteria for bulimia do not access medical help.
  • Of those who do:
    • 45% to 75% recover completely
    • 27% improve considerably
    • 23% have a chronic course
  • The crude mortality rate is approximately 0.32% to 3.9%
  • Most patients with bulimia nervosa continue an active life despite the disorder
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