I have suggested that deciding between competing treatments should involve a complicated but familiar algorithm that weighs four factors: chance of relief of suffering, risk of adverse event, cost and patient preference. [1] In suggesting that ethical decisions about management “also be informed by our models of disease processes” and “‘make sense’ in the light of [those] models”, Dr Pies appears to imply that interventions should be preferentially aimed at the organ with the pathology, and that pathological-organ-prioritisation bears some additional ethical weight in the decision. This cannot be true.

Of course, most of the time, our interventions will be aimed at the pathological organ. Sometimes, though, when that organ can’t be repaired, we will, and should, aim our interventions elsewhere. Cushing’s syndrome can occur when the pituitary gland, situated just beneath the brain, malfunctions. The malfunction causes the adrenal glands, located just above the kidneys, to produce too much cortisol. Rarely, when the pituitary abnormality cannot be corrected, doctors treat Cushing’s syndrome, by removing the patient’s normal adrenals. [2] Adrenalectomy “makes sense”, even though we know the pathology is actually in the pituitary. No one considers these operations ethically dubious.

Assuming that BIID is due to a brain malfunction, it would obviously be preferable, based on the four factors above, to fix the brain malfunction if that is possible. If it is not possible though, and currently there is little reason to feel that it is, then removing the patient’s normal leg may be the ethical treatment of choice. The fact we will be removing a normal ‘organ’ makes the treatment unusual, but not, in and of itself, unethical.