A hospital is being investigated for breaching the privacy of dozens of patients after medical records revealing a "swollen penis" and mental illnesses among other things, were found in a Coburg street.

The Australian Information and Privacy Commissioner Timothy Pilgrim is investigating how the records of 31 patients were removed from the John Fawkner Private Hospital in Melbourne's north last month.

John Fawkner Private Hospital Credit:Chris Hopkins

The documents included queries about whether a patient should be resuscitated if they have a cardiac arrest, and notes about a "swollen penis", depression, weight loss surgery, breast reduction surgery, dementia and incontinence.

The five pages of hand-over notes included the patients' names, ages, diagnoses, treatment plans, medications, how many days they'd been in hospital and whether they lived alone.