Infection after Posterior Lumbar Fusion (Not where you might think)

Infection is a serious risk factor after any surgery. In mild cases, infection after surgery means a course of antibiotics. Serious cases of postsurgical infection, however, may require admission to a hospital and perhaps a second surgery to treat the source of infection. While most people think of postsurgical infection as an infection in or around the surgical wound, another type of infection is common after posterior lumbar fusion, namely urinary tract infection or UTI. While UTI is not terribly serious in most people, when it occurs in patients after posterior lumbar fusion, it can have quite serious ramifications.

Risk of UTI after posterior lumbar fusion

In a posterior lumbar fusion, the surgeon makes an incision in the patient’s back along the spine. The spine surgeon moves through layers of back muscles and tissues until the vertebral bodies are in view. The spinal bones are fused together using hardware and/or bone grafts. For reasons that are not entirely clear, this procedure increases the risk of urinary tract infection in patients. In one study, 1.77% of people undergoing posterior lumbar fusion suffered a UTI as a result.

 The consequences of UTI after posterior lumbar fusion

Uncomplicated UTIs are rather common and very easy to treat. A short course of oral antibiotics is not enough to cure most cases. However, when UTI occurs after posterior lumbar fusion, it greatly increases the risk for a serious condition called sepsis. Sepsis is a potentially life-threatening reaction to an infection in the blood. In people with posterior lumbar fusion, 11.5% of patients with a UTI experience sepsis compared with 0.6% of surgical patients without a UTI. Moreover, 37% of surgical patients who experienced a UTI after surgery were readmitted to the hospital compared to only 5% of patients without a urinary tract infection.

Risk factors associated with UTI after posterior lumbar fusion

The risk of UTI after posterior lumbar fusion seems to be more common in some patients rather than others. Among these spine surgery patients, those who are older, female, or who have diabetes are at greater risk for developing a UTI. Likewise, malnourished individuals and people who are functionally dependent on others were more likely to develop urinary tract infection. Researchers also found the longer the posterior lumbar fusion surgery took to complete, the higher the patient’s likelihood of developing a UTI.

The reason for hope

While these results are certainly a cause for concern among surgeons and patients, they also reveal a treatable complication that can significantly impact the outcome of posterior lumbar fusion. Since we now know that almost one in 50 patients undergoing posterior lumbar fusion will have a potentially serious UTI, and that certain people are greater risk than others, patients and healthcare professionals can be vigilant for symptoms of UTI after orthopedic spine surgery. Early and aggressive treatment of UTI could presumably reduce the risk of serious infection and sepsis in these patients.

Symptoms of UTI

Urinary tract infection is a clinical diagnosis, which means it is based on symptoms rather than tests. While your physician may perform urinalysis to confirm a diagnosis, a UTI is diagnosed by these three symptoms:2

Dysuria- pain or discomfort during urination

Frequency – urinating more frequently than normal

Urgency – an acute need to urinate arising rather suddenly

More serious cases of UTI may also cause pain around the bladder and blood in the urine. It is important for patients and their physicians to look for UTI symptoms after posterior lumbar fusion surgery and provide effective antibiotic treatment.


  1. Bohl DD, Ahn J, Tabaraee E, et al. Urinary Tract Infection Following Posterior Lumbar Fusion Procedures: An ACS-NSQIP Study. Spine (Phila Pa 1976). 2015.
  2. Bent S, Nallamothu BK, Simel DL, Fihn SD, Saint S. Does this woman have an acute uncomplicated urinary tract infection? JAMA. May 22-29 2002;287(20):2701-2710.


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