A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
An 84-year-old man presents to the emergency department for a loss of consciousness. The patient states that he was using the bathroom when he lost consciousness and fell, hitting his head on the counter. The patient has a past medical history of diabetes, hypertension, obesity, factor V leiden, constipation, myocardial infarction, and vascular claudication. His current medications include lisinopril, atorvastatin, valproic acid, propranolol, insulin, metformin, and sodium docusate. The patient denies use of illicit substances. His temperature is 99.5°F (37.5°C), blood pressure is 167/98 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 98% on room air. Physical exam reveals an elderly man sitting comfortably in his stretcher. Cardiac exam reveals a systolic murmur heard at the right upper sternal border that radiates to the carotids. Pulmonary exam reveals mild bibasilar crackles. Neurological exam reveals 5/5 strength in his upper and lower extremities with normal sensation. The patient's gait is mildly unstable. The patient is unable to give a urine sample in the emergency department and states that he almost fainted again when he tried to. Which of the following is the most likely diagnosis?
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A
Postural hypotensionIncorrect. Postural hypotension is triggered by going from supine to standing with a documented BP drop; this patient is hypertensive and the trigger is voiding, not standing.
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B
SeizureIncorrect. Seizure typically causes postictal confusion, incontinence, tongue biting, or focal neurologic deficits; this patient has no such features.
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C
Cardiac arrhythmiaIncorrect. Cardiac arrhythmia (e.g., complete heart block, sick sinus, VT) causes syncope without a positional or behavioral trigger and may show ECG abnormalities — neither applies clearly here.
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D
Situational syncopeCorrect. Loss of consciousness specifically triggered by voiding (and again attempting to urinate in the ED) defines micturition (situational) syncope, a vagally-mediated reflex.
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E
Carotid sinus hypersensitivityIncorrect. Carotid sinus hypersensitivity causes syncope triggered by neck pressure, head turning, or tight collars, not by micturition; the voiding-triggered syncope described here defines situational (micturition) syncope.
↑ Tap an answer to reveal the reasoning
Answer: D. An elderly man who loses consciousness while attempting to urinate (and again when trying to provide a urine sample in the ED) has classic situational (micturition) syncope. The mechanism is a vagally-mediated reflex: during straining or voiding, sudden release of bladder pressure plus a Valsalva-like maneuver triggers an exaggerated parasympathetic response (bradycardia, vasodilation), reducing cardiac output and cerebral perfusion just long enough to cause syncope.
The diagnostic clue is the highly specific trigger — micturition (or, in other forms, defecation, coughing, swallowing). The patient remains hemodynamically stable between events and has no warning prodrome other than the situation itself. Other situational syncopes include cough syncope (in COPD) and post-prandial syncope (in the elderly).
Distinguishing from postural hypotension: orthostasis requires positional change with documented BP drop on standing; this patient's hypertension and the situational trigger argue against orthostasis. Cardiac arrhythmia typically lacks a positional/situational trigger and may show ECG abnormalities. Management is reassurance, sitting to void, and avoiding straining.
**Why each option:**
**A.** Postural hypotension is triggered by going from supine to standing with a documented BP drop; this patient is hypertensive and the trigger is voiding, not standing.
**B.** Seizure typically causes postictal confusion, incontinence, tongue biting, or focal neurologic deficits; this patient has no such features.
**C.** Cardiac arrhythmia (e.g., complete heart block, sick sinus, VT) causes syncope without a positional or behavioral trigger and may show ECG abnormalities — neither applies clearly here.
**D.** Correct. Loss of consciousness specifically triggered by voiding (and again attempting to urinate in the ED) defines micturition (situational) syncope, a vagally-mediated reflex.