Why is polyethylene glycol absorption a concern with Bactroban 2% ointment (mupirocin), particularly in moderate or severe renal impairment?

Polyethylene glycol in Bactroban 2% ointment (mupirocin) can be absorbed through open wounds and damaged skin and is excreted by the kidneys, so the ointment should not be used where large quantities could be absorbed, especially with moderate or severe renal impairment.