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

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.