X-ray is significantly less accurate than CT at grading stone burden in patients who undergo removal of encrusted and retained ureteral stents, misgrading a majority of patients who required multiple surgeries for removal of encrusted tubes, according to a study published in the February issue of The Journal of Urology.
Ureteral stent placement plays an important role in managing urinary tract infections, with co-indications for nephrolithiasis, ureteral stricture, malignancy and retroperitoneal fibrosis. The tubes are typically removed within three to 12 months of placement, though they can become encrusted, setting off complications ranging from irritative voiding, urinary tract obstruction and loss of renal function to severe infection and even death.
The researchers considered proximal stone burden to be the most important factor associated with complicated removal of ureteral sents, hypothesizing that abdominal/pelvic CT would more accurately estimate forgotten, encrusted and calcified (FECal) score and associated stone burden than the calculations provided by x-rays of the kidneys, ureters and bladder (KUB).
The researchers removed a total of 55 encrusted and retained ureteral stents and one nephrostomy from 52 patients, with the average tube having stayed in patients for 24.9 months. Ninety-four percent of tubes were removed endoscopically, while 21 percent of patients required multiple surgeries to extract the tubes.
CT graded stone burden with significantly greater accuracy than KUB, 95 percent compared with 64 percent. In addition, KUB underestimated proximal stone burden in 44 percent of patients who underwent multiple surgeries, misgrading 67 percent of these patients, including four in whom plain x-ray missed significant proximal calculus burden.
“Using the FECal grading system, which correlated well with the amount of stone burden [r=0.56 for KUB and 0.62 for CT], we found that CT accuracy was 94.9 percent. If used alone, plain film x-ray could underestimate proximal encrustation, and lead to poor operative preparation, complications and the need for unanticipated additional surgery,” said John W. Weedin, MD, from the department of urology at Baylor College of Medicine in Houston.
“Our study demonstrated the superior accuracy of CT compared to KUB to evaluate stone burden associated with encrusted ureteral stents,” Weedin concluded.