After placing a ureteral stent or a nephrostomy tube –for a stone, obstruction, urine leak, or trauma–, what are the consequences of doing nothing for weeks or months?
Ureteral stents placed to relieve obstruction from cancer are typically changed every 3-6 months. The morbidity of these long term stents is minimal. On the other hand, long term nephrostomy tubes are sometimes changed every 6 weeks to avoid problems.
In an older study, 25 patients with 27 nephrostomies placed into a sterile system were followed until they developed bacteriuria (> 10,000), candiduria or pyuria (>5 WBC). Some patients had one dose of antibiotics at the time of placement of the nephrostomy tube. At 6 weeks, 5 tubes failed to develop pyuria or bacteriuria. The other 22 tubes demonstrated bacteriuria or candiduria and pyuria within 2-9 weeks (mean of 6 weeks). Four patients that were placed on continuous prophylaxis developed either bacteriuria, candiduria or pyuria at 3,3,7 and 9 weeks. Two of these 4 patients developed candiduria. No patient developed any clinical symptom. Cultures preferentially grew Pseudomonas, Enterococcus, and candida, as opposed to E. Colli. The authors hypothesized that the reason there were no symptoms was due to the fact that urine was flowing uninterrupted. The conclusion from this study was that prophylaxis was not necessary and cultures could be ignored as long as adequate drainage persists with a patent tube.
A more recent study found an incidence of pyelonephritis of 19% in patients that had a nephrostomy tube placed due to cancer. The majority of pyelonephritis in this study developed in the first 40 days after nephrostomy tube placement. Prophylaxis did not seem to prevent pyelonephritis in this study either.
Anecdotally, I had a toddler develop severe pseudomonas pyelonephritis despite prolonged treatment with broad-spectrum antibiotics before and after the tube was placed, and continuous Nitrofurantoin prophylaxis:
In a large multicenter pediatric nephrostomy tube study of 675 procedures, a urinary tract infection was diagnosed in 5% of the cohort after the procedure.
The above evidence suggests the pyelonephritis does occur with a nephrostomy tube in place and that continuous antibiotic prophylaxis does little to prevent it.
With regards to ureteral stents, this study in adults showed also an 18% incidence of symptomatic urinary tract infection. They identified longer duration of the stent (most patients that developed a UTI had the stent for more than 150 days), diabetes, and chronic renal failure as risks factors for infection. E colli was the most common organism. These authors recommended replacing the ureteral stent after treating the infection.
This prospective study performed in adults showed that ureteral stents start getting colonized at 2 weeks and that the rate of colonization increased with longer periods of stenting.
In a uncontrolled retrospective study published recently, antibiotic prophylaxis was associated with a reduced rate of symptomatic UTI, from 25% in the control group to 7% in the antibiotic group.
UTI’s do occur in about 1/5 of patients with stents or nephrostomy tubes. Prophylaxis appears to reduce the rate of UTI’s in patients with stents but not those with nephrostomy tubes. In patients with nephrostomy tubes, it is key to maintain patency of the tube to prevent infection.