The unproven utility of preoperative urinalysis. Clinical use.

We investigated the utility, ie, relevance to clinical outcome, of routine preoperative urinalysis with a retrospective study of 200 clean-wound, orthopedic, nonprosthetic knee procedures. Physicians primarily order a preoperative urinalysis to detect infection, because of the purported relationship between remote infection and surgical wound infection. We found that preoperative urinalysis is uniformly ordered, with a high prevalence of abnormal results (15%) but a low physician-response rate (29%). Wound infection was rare, but there was no difference in frequency of wound infection between patients with normal and abnormal results of urinalysis. We conclude that the utility of routine preoperative urinalysis is unproven. Current practice does not agree with the rationale for ordering this test, nor does published literature support it. Although data are inadequate to fully define the appropriate use of preoperative urinalysis, we suggest clinical recommendations and avenues for further research.