The correct answer is:

Vomiting; electrolytes

Key Point:

Prolonged intervals between bowel movements suggests little food getting beyond the stomach.

Explanation:

This patient most likely has anorexia (bulimia/purging type) with repeated vomiting resulting in little food getting beyond the stomach, thus the infrequent bowel movements.

Bradycardia, hypotension, cold extremities and hypomenorrhea are all signs of hypometabolism, consistent with the diagnosis of anorexia.

The pitting of her teeth is an indication of loss of enamel through repeated exposure to gastric acid. Finally, the infrequency of bowel movements in a late adolescent, added to the rest of the findings, leads to the preliminary diagnosis of anorexia.

Of course, the patient could have denied vomiting but often some hesitation or unexpected body language is observed when asked about this symptom.

Hypotension and polyuria could suggest adrenal insufficiency but a slow pulse speaks against the diagnosis as does the pronounced infrequency of bowel movements.

The combination of bradycardia and low body temperature could suggest hypothyroidism but low blood pressure would not be expected and, like adrenal insufficiency, the striking absence of bowel movements exceeds the degree of constipation observed in patients with hypothyroidism.

Anorexia with repeated vomiting will result in a hypokalemic, hypochloremic alkalosis, the result of gastric fluid losses from vomiting. None of the other diseases in the differential diagnosis would result in electrolyte abnormalities or abnormal kidney function studies.Gastric analysis should be normal. Colonoscopy in this young woman would not be expected to be abnormal, regardless of which diagnosis was correct.

Other elements of the history that were not asked (thirst, voice change, or night sweats) could support diagnoses of adrenal insufficiency, hypothyroidism, and inflammatory processes respectively) but are not observed in patients with anorexia.

An important point in this case is that when the history and physical examination present a confusing mix of symptoms and signs, it is wise to go back over the patient’s history and ask oneself whether some aspect of the history that was not asked about might be helpful to explore.In this case, of course, it was the failure to ask about vomiting.

This case reinforces the importance of a good history and physical examination, leading to a much narrower set of diagnostic possibilities and thus more targeted laboratory studies and/or diagnostic procedures.

Figure:

Tooth damage (pitting) in bulimic patient.

References:

Kreipe RE, Starr, TB. Eating Disorders. Nelson Textbook of Pediatrics. 2020; 41: 228-236.e1

Tanofsky-Kraff M. Eating Disorders. Goldman-Cecil Medicine. 2016; 206: i416-1418.e1