Eating disorders: anorexia nervosa

Chapter 25 EATING DISORDERS


ANOREXIA NERVOSA




KEY POINTS



• Anorexia nervosa (AN) is characterised by a refusal to maintain a healthy body weight; resistance to gain weight, an intense fear of gaining weight, disturbance in the way in which shape or weight is experienced and denial of the seriousness of an individual’s current low body weight.

• Assess carefully for protein–calorie restriction.

• Medical complications can include non-alcoholic steatohepatitis.

• Refeeding syndrome may occur if calorie intake is increased too rapidly, leading to sudden death.

• The overall mortality of AN is 5%.


INTRODUCTION


Eating disorders have been the focus of increasing community and professional awareness in recent years. They form a heterogeneous group of illnesses that affect adults, adolescents and, more rarely, children. Anorexia nervosa (AN) is a specific eating disorder and the third most common chronic illness in adolescent females. It affects one in 200 girls between the ages of 15 and 19 years. Males develop AN less commonly, with the male to female ratio between 1:10 and 1:20. The increasing incidence of eating disorders and their impact on the health of a new generation of young people are of particular concern.


Clinicians need to think about eating disorders in patients presenting with weight loss, anorexia or malnutrition.


The key diagnostic features of AN are:


• Refusal to maintain a healthy body weight and resistance to weight gain. There can be a history of weight loss to less than 85% of expected weight for age, sex and height, or a failure to gain expected weight during a period of growth.

• An intense fear of gaining weight or becoming fat even though underweight.

• Disturbance in the way in which body shape or weight is experienced and reported, or denial of the seriousness of the current low body weight.

• Amenorrhoea in post-menarchal patients (i.e. the absence of at least three consecutive menstrual cycles).

The subtypes of AN are:


• Restricting type—during the current episode the patient has not engaged in binge eating or purging behaviour (i.e. self-induced vomiting or the misuse of laxatives, diuretics or enemas)

• Binge-purge type—during the current episode the patient has regularly engaged in binge eating or purging behaviour, on at least three occasions a week, for at least 3 months.


ASSESSMENT



History


After noting the cause for presentation, it is important to take a full history of how the low weight has occurred. This includes the change in weight, particularly noting the maximum and lowest weights, or alternatively change in clothes size. It is important to inquire about dietary intake and eating or purging behaviour. Additionally, the amount and intensity of exercise regimens should also be recorded as a significant minority of patients with AN use strenuous exercising as a major strategy to manipulate their weight.


An inquiry should also be made as to how the patient perceives their body shape, weight and health. Body dissatisfaction—if the patients feels their body is fat or would want to change aspects of their body in which fat is deposited—should also be recorded.


Menstrual history, including the duration of amenorrhoea, and sexual history are important. Bone size and mineralisation are influenced by the duration of amenorrhoea as well the severity of malnutrition.


Family structure and history, as well as history of comorbid psychiatric or medical conditions, are also important information to record at the time of initial assessment.



Physical findings


The protein–calorie malnutrition (PCM) that accompanies AN affects every organ in the body. The clinical presentation may have a number of features in common with hypothyroidism (Table 25.1); mentation and locomotion are slowed, hypothermia, constipation, pretibial oedema may be present, however patients do not have a goitre and thyroid hormones (thyroid stimulating hormone [TSH] and thyroxine [T4]) remain within normal parameters. Triiodothyronine (T3; measured by radioimmunoassay) is depressed commensurate with the degree of PCM, and recovers with correction of the malnutrition.


TABLE 25.1 Medical differential diagnosis of anorexia nervosa






• Hypothyroidism

• Inflammatory bowel disease

• Type 1 and 2 diabetes

• Addison’s disease

• Systemic lupus erythematosus

• Brain tumour

On initial inspection, the patient has a wasted appearance with lanugo (fine downy hair) present over the torso and limbs. There is often a generalised pallor with peripheral cyanosis. Capillary refill is delayed (more than 2 seconds). The hands are cool and peripheral pulses are slow and low in volume. Although the circulating volume and red cell mass is decreased, pallor is usually not observed in the palmar creases or conjunctiva. Blood pressure is maintained though there is often a postural drop in excess of 15 mmHg with moderate or severe protein–calorie malnutrition.


Heart sounds tend to be soft. Pericardial effusions are reported in severe PCM, and occur particularly in those patients with very low thyroid hormone (T3).


The abdomen is scaphoid and skin over the anterior abdominal wall is lax. Muscles of the anterior abdominal wall are typically decreased permitting palpation of abdominal organs easily. An enlarged fatty liver (with a soft, smooth, non-tender lower border) is commonly detected. Stool in the sigmoid colon is also easily palpable in the left lower quadrant.


Oedema around the sacrum and pretibial areas may be present, though this usually occurs with refeeding rather than at initial presentation. Inspection of the feet is also important. The decreased peripheral circulation, particularly in patients who exercise excessively, may lead to signs of peripheral vascular insufficiency as well as poor hygiene (and a potential for sepsis).


Clinical findings may vary with patients who have more chronic AN and have adapted to the long standing PCM. These patients are haemodynamically compensated.



Investigations


Baseline investigations are useful in screening for micronutrient deficiencies as well as excluding differential diagnoses, particularly for atypical presentations. A low erythrocyte sedimentation rate (ESR) is typical of anorexia nervosa and distinguishes the eating disorder from malignancies, as well as inflammatory and autoimmune conditions.


Specific evaluation for micronutrient deficiency (e.g. iron, vitamins, trace elements) are unlikely to be clinically useful at initial evaluation.


• Blood tests
– Full blood count

– Erythrocyte sedimentation rate

– Urea, electrolytes, creatinine

– Liver function tests

– Blood sugar level

– Calcium, magnesium, phosphate

– Follicle stimulating hormone, luteinising hormone, oestradiol

Related posts:

Chronic pancreatitis Colorectal cancer screening Inflammatory bowel disease Suspected iron overload or high serum ferritin Pregnancy and liver disease Obesity surgery

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Mar 29, 2017 | Posted by in GASTROENTEROLOGY | Comments Off on Eating disorders: anorexia nervosa

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