The incidence of postoperative urinary retention in patients undergoing elective hip and knee arthroplasty

INTRODUCTION Postoperative urinary retention requiring urethral catheterisation increases the risk of joint sepsis following arthroplasty. Spinal anaesthesia with opiate administration is used widely in lower limb arthroplasty. We sought to establish whether the choice of opiate agent had any effect on the incidence of postoperative retention and therefore the risk of joint sepsis. METHODS A total of 445 consecutive patients who underwent primary elective lower limb arthroplasty were reviewed retrospectively. Patients had general anaesthesia and femoral nerve block (GA+FNB), spinal anaesthesia and intrathecal fentanyl (SA+ITF) or spinal anaesthesia and intrathecal morphine (SA+ITM). RESULTS Urinary retention was observed in 14% of male and 2% of female patients with GA+FNB, 9% of male and 3% of female patients with SA+ITF, and 60% of male (p=0.0005) and 5% of female patients with SA+ITM. Men who experienced retention were older (68 vs 64 years, p=0.013) and had longer inpatient stays (6.7 vs 4.6 days, p=0.043). Fewer patients in the SA+ITM group required breakthrough analgesia (28% vs 58%, p=0.004). CONCUSIONS The use of ITM in men significantly increases the incidence of urinary retention requiring urethral catheterisation and subsequently increases the risk of deep joint sepsis. Its use should be rationalised against the intended benefits and alternatives sought where possible.