LSD 'flashback' as a cause of diagnostic error.

An emaciated, but otherwise physically normal young man presented with an acute psychosis resembling hallucinogenic drug abuse. His behaviour was so strange that the underlying pathology of severe pyloric stenosis was only detected when a chance measurement of urea and electrolytes was made, revealing gross biochemical abnormalities. His abnormal mental state persisted for more than one week and an LSD 'flashback' was postulated as the cause of the prolonged psychosis