Diagnosis: Bulimia Nervosa
The diagnosis for binge eating with purging is bulimia nervosa (BN), characterized by recurrent episodes of binge eating followed by compensatory purging behaviors (self-induced vomiting, laxative use, diuretics) to prevent weight gain 1, 2.
Diagnostic Criteria and Assessment
To establish this diagnosis, you need to document:
- Binge eating episodes: Recurrent consumption of large amounts of food with a sense of loss of control
- Purging behaviors: Self-induced vomiting, laxative misuse, diuretic abuse, or other compensatory methods
- Frequency: These behaviors must occur at least weekly (though monthly frequency represents subthreshold BN) 1, 3
- Body image disturbance: Excessive preoccupation with weight and body shape that drives these behaviors 2
Initial Evaluation Requirements
The 2023 APA guidelines 1 specify you must:
Quantify the behaviors precisely:
- Frequency of binge episodes per week
- Frequency and types of purging methods used
- Duration of symptoms
- Percentage of time preoccupied with food/weight/body shape
Physical examination findings to document:
- Vital signs including orthostatic changes (hypotension, tachycardia)
- BMI calculation
- Signs of purging: parotid gland enlargement, dental enamel erosion, Russell's sign (calluses on knuckles), sore throat 1, 4
Required laboratory workup:
- Complete blood count
- Comprehensive metabolic panel with electrolytes (hypokalemia, hypochloremia, metabolic alkalosis are common)
- Liver and renal function tests
- ECG is mandatory given severe purging behavior to assess for QTc prolongation 1
Severity Assessment
Severity is determined by purging frequency per DSM-5 criteria, though recent evidence 5 suggests considering both the number of purging methods used AND binge-eating frequency provides a more complete picture. Higher purging frequency correlates with lower BMI and greater eating disorder psychopathology.
Important Diagnostic Considerations
Diagnostic crossover is common 3: 26% of patients transition between eating disorder diagnoses during follow-up, with BN most frequently crossing to purging disorder. This means you should reassess diagnosis periodically rather than assuming diagnostic stability.
Rule out other conditions:
- Anorexia nervosa, binge-purge subtype (if BMI is significantly low)
- Binge eating disorder (binge eating without regular purging)
- Purging disorder (purging without objective binge episodes)
Screen for psychiatric comorbidities 1: Depression, anxiety disorders, and substance use disorders are highly prevalent and must be identified as they affect treatment planning.
Critical Pitfall
Do not wait for medical complications to make the diagnosis. While electrolyte abnormalities and cardiac changes confirm purging severity, their absence does not rule out BN. The diagnosis is clinical, based on behavioral patterns and psychological features 1, 2.