Table 1 Unmodifiable and modifiable risk factors

Demographic variables, such as gender and age, BMI, maximum bladder capacity, co-morbidity (hypertension and diabetes)

Drugs used, such as beta blockers, benzodiazepines and anti-depressive/anti-psychotic drugs.

Pre-medication with benzodiazepines and/or NSAID’s,

Bladder volume/residual volume before start of surgery, time since last voiding.

Type of surgery, divided in head-neck, thorax/back/breast, lower abdominal or lower extremities, duration of surgery.

Type of anesthesia; general or spinal (divided in short-acting articaine and long-acting bupivacaine), cardiovascular drugs such as atropine, ephedrine, and/or phenylephrine, opioids.

Bladder volume after arriving at PACU, total sum of opioids needed, drugs given such as cardiovascular therapeutics, opioids, anti-emetics, total volume infused or taken.