Signs of Ureteral Stent Infection: What You Need to Know

Ureteral stent infections share many symptoms with the ordinary discomfort that stents cause on their own, which is precisely what makes them tricky to spot. Fever is the clearest red flag that separates infection from routine stent irritation, but the earlier signs, like worsening urinary burning, increased urgency, and cloudy or foul-smelling urine, overlap heavily with the baseline symptoms most stented patients already experience. Roughly one in five patients with a double-J stent develops a symptomatic urinary tract infection during the stenting period, so this is not a rare complication to worry about only in theory.¹

Why Stent Infections Are Easy to Miss

The core problem is that a ureteral stent, even when functioning exactly as designed, causes symptoms that feel a lot like a urinary tract infection. Most patients with stents report bothersome urinary symptoms including frequent urination, urgency, burning during urination, and pain in the flank or lower abdomen.² When an actual infection develops on top of those baseline complaints, the early signs can feel like the same discomfort getting a little worse rather than something categorically new.

Even with preventive antibiotics, up to about 30% of stented patients still develop stent-associated urinary tract infections.³ The overlap between “normal stent discomfort” and “early infection” is so significant that clinicians themselves acknowledge the diagnostic challenge. Without fever to differentiate the two, many infections go unrecognized until they progress.

Early Warning Signs

The symptoms worth paying close attention to are changes from your baseline. If you have had a stent for a few days or weeks and have settled into a pattern of manageable discomfort, a sudden worsening of urinary symptoms is worth reporting to your doctor. In a prospective study of 80 patients with double-J stents, lower urinary tract symptoms such as painful urination, increased frequency, and urgency were significantly associated with stent colonization and subsequent infection.¹

The early signs that should prompt you to contact your urologist include:

Increased burning: Dysuria that gets noticeably worse after a period of relative stability, rather than the mild burning many patients have from day one.
More frequent urination: Needing to go significantly more often than your established stent-related baseline.
Cloudy or foul-smelling urine: A change in urine appearance or odor that was not present before.
New or worsening flank pain: Pain in the side or back that escalates beyond what you experienced in the first days after stent placement.
Blood in urine: Some blood-tinged urine is common with stents, especially after activity, but a marked increase in hematuria can signal infection or encrustation.

None of these symptoms in isolation is definitive. The pattern that matters is change from your personal norm. A patient who has had mild urgency for two weeks and then suddenly cannot get through 30 minutes without a bathroom trip is experiencing something different from baseline stent irritation.

When It Becomes an Emergency

Fever is the symptom that transforms a suspected stent infection from a “call your urologist” situation into a “go to the emergency department” situation. An international survey of urologists used a clinical scenario of a patient with a chronic indwelling ureteral stent presenting with fever, rapid heart rate, and flank pain as a representative case of infected stent requiring urgent management.⁴ That combination of symptoms, fever plus tachycardia plus pain, signals that bacteria may be spreading beyond the urinary tract.

The serious concern is urosepsis, a condition where pathogens from the urinary tract enter the bloodstream. In severely infected patients, urosepsis carries a mortality rate of up to 50%.⁵ That number sounds alarming, and it should: it is the reason urologists take fever in a stented patient very seriously. Symptoms that should send you to the emergency room include:

Fever above 38°C (100.4°F): Especially if accompanied by chills or rigors.
Rapid heart rate: Feeling your heart pounding or racing at rest.
Severe flank pain: Pain that is markedly worse than anything you experienced in the days after stent placement.
Confusion or lightheadedness: Signs that infection may be affecting your blood pressure or systemic function.
Nausea and vomiting: Especially combined with fever and pain.

If you have a stent and develop a fever, do not wait to see if it resolves on its own. The window between a treatable febrile UTI and full-blown sepsis can be narrow.

Why Stents Get Infected So Easily

Within minutes of being placed, a ureteral stent begins accumulating a layer of proteins, sugars, and other molecules from urine and blood. This “conditioning film” changes the stent’s surface in ways that make it friendlier to bacteria.⁶ Bacteria then attach to this coated surface and begin building a biofilm, a structured community of microorganisms embedded in a protective matrix. Once a mature biofilm forms, it becomes extremely difficult to eliminate with antibiotics alone, because the matrix shields the bacteria inside it.⁵

The numbers bear this out. In one study of 129 patients, about 83% of removed stents showed positive biofilm cultures.⁷ That does not mean 83% of those patients were sick; colonization (bacteria living on the stent) and clinical infection (bacteria causing symptoms) are not the same thing. But it does mean the vast majority of stents harbor bacteria, and the line between quiet colonization and active infection can shift with changes in the patient’s immune status, stent dwell time, or bacterial load.

Some bacteria are particularly good at this. Certain species produce urease, an enzyme that raises the pH of urine and causes mineral crystals to precipitate on the stent surface. This encrustation makes the biofilm even more entrenched and harder to treat.⁸ The combination of biofilm and mineral encrustation is one reason why stent infections tend to be stubborn and why simply prescribing antibiotics without addressing the stent itself often fails.

The Bacteria Involved

Escherichia coli is the most common culprit in stent infections, which is no surprise since it dominates urinary tract infections in general.⁹ But stent-related infections have an interesting wrinkle: the bacteria growing on the bladder end of the stent do not always match the bacteria on the kidney end. Research has found that Pseudomonas and Enterococcus faecalis show up more often in the bladder portion, while Enterococcus faecium tends to be more common in the renal pelvis.⁹

This microbial inconsistency matters for treatment. It means a urine culture taken from a voided sample, which reflects what is in the bladder, may not represent the organisms causing problems higher up in the urinary tract. Drug resistance rates among biofilm-associated bacteria also tend to be higher than among free-floating organisms in urine.⁷ This is why clinicians sometimes culture the stent itself when it is removed, not just the urine, to get a better picture of what is actually growing on the device.

Why Diagnosis Requires More Than a Dipstick

Here is something many patients do not realize: a standard urinalysis is unreliable for diagnosing infection in someone with a stent. The stent itself can cause white blood cells and other markers to appear in the urine even without infection, simply because the foreign body irritates the urinary tract lining. Research has shown that positive findings on urinalysis in patients with indwelling ureteral stents have a poor correlation with actual positive urine cultures.¹⁰

A proper urine culture is warranted when infection is suspected. Even then, as discussed, the culture may not capture organisms living higher up on the stent. If you are experiencing worsening symptoms and a urine culture comes back negative, that does not necessarily rule out a stent-related infection. Discuss with your urologist whether stent culture at the time of exchange or removal would be appropriate.

When infection is severe enough to cause obstruction of the kidney, imaging becomes important. Ultrasound can detect signs of fluid and debris in the collecting system, and CT scanning provides more detailed information when ultrasound is inconclusive.¹¹ These imaging studies help determine whether a stent infection has progressed to pyonephrosis (pus in the kidney), which is a surgical emergency.

Who Is at Higher Risk

Not every stented patient faces the same odds of infection. Several factors consistently raise the risk:

Stent dwell time is one of the strongest predictors. In one study, the rate of pre-procedure UTI was about 4% when the stent had been in place for less than one month, compared to roughly 26% when the stent had been left for longer than a month.¹² The longer a stent stays in, the more time bacteria have to colonize and build mature biofilms. This also aligns with data from transplant patients, where early stent removal (before 21 days) was associated with roughly half the risk of stent-related UTI compared to later removal.¹³

A prospective cohort study identified several other independent risk factors for febrile stent-associated UTIs: being female, having multiple medical conditions, having a urethral stent placed at the same time, and having had a UTI within the prior three months.¹⁴ A history of recurrent UTIs and higher body mass index have also been linked to worse stent-related symptoms in the later phase of stent placement.¹⁵

If you fall into any of these higher-risk categories, it is worth being especially vigilant about monitoring your symptoms and proactive about scheduling follow-ups.

Treatment When Infection Develops

Treating a stent infection is not as simple as prescribing a course of antibiotics and moving on, though antibiotics are part of the picture. The biofilm on the stent acts as a reservoir of bacteria that antibiotics in the bloodstream and urine cannot fully penetrate. Because of this, management strategies vary widely, and no single protocol dominates clinical practice.¹⁶

For mild infections caught early, targeted antibiotics based on urine culture results may be sufficient to control symptoms while the stent remains in place. But for persistent or severe infections, exchanging the stent (removing the colonized one and placing a new one) is often considered. The logic is straightforward: if the biofilm is the source of ongoing bacterial seeding, removing the physical substrate removes the problem at its root. Stent culture at the time of exchange can also help guide antibiotic selection, since the organisms on the stent may differ from those in voided urine.¹⁶

In cases of febrile UTI or suspected urosepsis, treatment is more aggressive and typically involves intravenous antibiotics, urgent stent removal or exchange, and sometimes placement of a nephrostomy tube to drain an obstructed, infected kidney. This is hospital-level care, and delay worsens outcomes.

Reducing Your Risk

The most effective way to reduce the chance of stent infection is to keep the stenting period as short as medically possible. If your stent is in place for a defined recovery window after a procedure, ask your urologist to confirm the planned removal date and keep that appointment. A “forgotten” stent, one left in longer than intended because a follow-up was missed, carries sharply increased risks of infection, encrustation, and even stent fragmentation.

Staying well-hydrated helps maintain urine flow through and around the stent, which makes it harder for bacteria to establish themselves. There is no magic volume, but the goal is to keep your urine dilute and pale rather than concentrated and dark.

Researchers are also working on the stent materials themselves. Drug-eluting stents and stents with antimicrobial surface coatings are the most studied approaches for reducing biofilm formation and infection.¹⁷ These technologies are not yet standard practice in most hospitals, but they represent a promising direction, and some coated stents are already in clinical use.

Encrustation, the mineral buildup that gives bacteria extra protection, has been targeted with oral supplements designed to modify urine pH. One multicenter trial found that a specific oral composition reduced stent encrustation rates compared to placebo.¹⁸ However, a separate randomized study testing alkaline citrate medications found no significant difference in encrustation rates.¹⁹ The evidence on pH modification is mixed, and no single supplement has become a standard recommendation.

Stent Infections During Pregnancy

Pregnant patients with ureteral stents face a unique set of challenges. The physiological changes of pregnancy, including hormonal effects on the urinary tract and physical compression of the ureters by the growing uterus, increase the baseline risk of urinary complications. In a study of pregnant patients with renal colic who received ureteral stents, about one in five developed a UTI. The strongest independent risk factors were a positive urine culture at the time of stent placement, larger kidney stones, and earlier gestational age at the time of stenting.²⁰

E. coli was again the most commonly identified organism in these infections. Management during pregnancy requires careful coordination between urology and obstetrics, since some antibiotics are contraindicated and imaging options like CT carry radiation risks. When stent encrustation or infection necessitates removal or exchange, every endoscopic procedure must be preceded by appropriate imaging to determine the safest strategy for both the mother and the fetus.²¹ Pregnant patients with stents should be monitored more frequently and should report any symptom changes promptly, given the elevated baseline risk.

The Quality of Life Dimension

Even without infection, ureteral stents substantially affect daily life. Research has consistently documented that patients with stents experience increased lower urinary tract symptoms and significantly reduced quality of life.²² About 80% of patients report bothersome urinary symptoms and stent-related pain, and as many as 40% experience sexual dysfunction while the stent is in place.²

This context matters because it shapes how patients interpret potential infection symptoms. If you already feel miserable from the stent itself, it is natural to attribute worsening symptoms to “just the stent” rather than to consider that infection has developed. The practical takeaway: do not normalize escalating symptoms. Your baseline may be uncomfortable, but it should be relatively stable. A meaningful shift in the character or intensity of your symptoms, even if it seems like “more of the same,” deserves medical evaluation rather than stoic endurance.

Structured patient education programs have shown real benefits. In one trial, patients who received empowerment-based continuity of care had lower complication rates than those receiving standard follow-up, along with better self-care scores and treatment compliance.²³ Knowing what to expect from your stent, understanding what symptoms to monitor, and having clear instructions about when to seek help make a measurable difference in outcomes. If your surgical team did not provide detailed written guidance about stent care and warning signs before you left the hospital, ask for it.

1
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2
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3
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13
PubMed Central. The Impact of Timing of Stent Removal on the Incidence of UTI, Recurrence, Symptomatology, Resistance, and Hospitalization in Renal Transplant Recipients
14
PubMed. Epidemiology and risk factors for febrile ureteral stent-associated urinary tract infections: A prospective observational cohort study
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PubMed. Does alkalinised urine reduce the rate of encrustation in patients with ureteric stents? A randomised controlled study
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PubMed. Risk Factors of Urinary Tract Infection After Ureteral Stenting in Patients with Renal Colic During Pregnancy
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