The Pope is dying in a quiet and undramatic way, writes Dr Muiris Houston.
The Pope has suffered a number of serious but likely interlinked medical events in the last 36 hours, the combined effect of which is to have rendered him critically ill.
Initially the Pope developed an infection in his urinary tract. Often referred to as a kidney infection, this is a relatively common occurrence in older patients with reduced mobility.
The incomplete voiding of urine meant that stagnant urine accumulated in his urinary tract; this is a perfect growth medium for bacteria.
Because he has been debilitated by ongoing illness, the Pope would have found it difficult to fight off the infection.
It is not uncommon in such a scenario for the infection to travel into the blood stream leading to a condition called septicaemia.
When this occurs highly toxic chemicals are released into the body.
They cause toxic shock and put all bodily organs under pressure. As his heart was affected by these toxins, the Pope's blood pressure dropped, leading in turn to heart failure.
The combined effect of these events means that his kidney, liver and brain functions will gradually deteriorate.
As his urinary output drops, waste products gather in the body and the Pope will drift in and out of consciousness.
The decision not to move him to the Gemelli Hospital is undoubtedly the correct one. As a dying man, his doctors and advisers will be aware of his desire to spend his last hours in the familiar surroundings of the papal apartment.
The Pope is dying in a quiet and undramatic way. He is unlikely to be in pain. As his level of unconsciousness deepens he will slowly and gradually reach the point where his respiratory and cardiac functions cease and death occurs.