I learned a great deal about truth-telling from a young woman who had multiple admissions to the hospital for critically low potassium levels in her blood stream, making her vulnerable to serious and even fatal heart irregularities.
It was significant that her potassium levels remained normal after replacement in the hospital but regularly dropped to critical levels after discharge, bouncing her back into the hospital.
The evaluation of low potassium (hypokalemia) includes a number of sophisticated and esoteric tests which in her case were all normal.
A common cause, however, is the surreptitious abuse of laxatives, especially in patients with a background of anorexia nervosa. In these individuals the key to confirming the laxative abuse is to firstly consider it after ruling out other causes with laboratory investigations.
My patient fervently denied the use of laxatives and she resented my probings into the matter. She accused me of not trusting her which often left me, despite my growing belief that I had good reason not to trust her, with pangs of guilt, especially when she often appeared misunderstood or hurt.
Hospital visits became increasingly strained as feelings of guilt (she hit the guilt target flawlessly) and suspicion (I was virtually certain that she was not being honest) competed for my attention.
We were at an impasse.
I spoke to a colleague in psychiatry about the case, especially as people with laxative abuse often have serious emotional distress.
He asked me if I told her I did not believe her. I had not, probably because it would have left me open to feelings of insensitivity. But that was what he thought was needed and I determined to tell her I did not believe her, despite my anxieties about confrontation, on the next visit.
So the next day I visited her in her hospital room and told her that I did not believe her and felt she had been secretly taking large doses of laxatives.
What followed was a thorough bombing, with everything within reach - lamps, glasses, books - flying at me as I fled the room.
It was not immediately apparent that truthfulness had served me well, but the next day I encountered a different person. She was tearful, apologetic and confessed that she had been abusing laxatives.
She had a serious condition and I was relieved that we could finally begin treating her. She was too.
This case reminds me of how amazing the truth can be, especially when it is painful.