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Evidence in the ED Renal Stones

Evidence in the ED Renal Stones. Is a KUB an Appropriate Imaging Technique for Renal Stones? TJ Lydon, MD PhD. Twinem, Am J Surg 17:389-394, 1932. “10% of urinary calculi cast no shadows at all.”

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Evidence in the ED Renal Stones

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  1. Evidence in the EDRenal Stones Is a KUB an Appropriate Imaging Technique for Renal Stones? TJ Lydon, MD PhD

  2. Twinem, Am J Surg 17:389-394, 1932 • “10% of urinary calculi cast no shadows at all.” • Analysis of 207 calculi reveal that 16 (7.7%) were composed of uric acid and 6 (2.9%) were cystine. • Radiographs and photographs of a second set of calculi demonstrated that uric acid stones cast no shadows while cystine “cast faint shadows.”

  3. New Imaging Technique: Spiral CT • Fielding et al, J Urology, 157(6):2071, 1997: Spiral CT is 98% sensitive and 100% specific for stone detection. • Vieweg et al, J Urology, 160(3):679, 1998: Spiral CT is 98% sensitive and 98% specific for stone detection.

  4. Fielding et al, Urology, 1997 • 100 ED pts with acute flank pain • Exclusion criteria were fever, chills, or pregnancy • By spiral CT, 55/100 had renal stones • All pts were followed by urology either with a clinic visit or by telephone interview. • Outcomes were resolution of symptoms, documented passage of stone, or retrieval of the stone by retrograde urography (aka, IVP). • 11 patients did not have adequate follow-up.

  5. Compare KUB to Spiral CT • Levine et al, Radiology, 204: 27-31, 1997: KUB has a 45% sensitivity and a 77% specificity (178 patients with acute flank pain). • Hamm et al, Euro Uro, 39:460-465, 2001: KUB has 46% sensitivity and 76% specificity (125 patients with acute flank pain). • Zagoria et al, AJR, 176:1117-1122, 2001: KUB detected 53% of calculi (26 patients with stones).

  6. Levine et al, Radiology, 1997 • 178 pts presenting to ED with acute flank pain and had a spiral CT as part of their work-up. All had KUB’s. • CT scans were reviewed retrospectively by two radiologists blinded to the results of the KUB. • KUB’s were read three times: first by the radiologist covering the ED, then a blinded retrospective reading by two radiologists, finally, a repeat retrospective reading by the same two radiologist who were un-blinded to the results of the CT scans.

  7. Levine et al, Radiology, 1997 • When the ED radiologist’s KUB reading was compared to the spiral CT: KUB had a sensitivity of 45% and a specificity of 77%. • When the two blinded radiologists’ retrospective reading was compared to the CT: KUB had a sensitivity of 59% and a specificity of 71%. • When the two radiologists re-read the KUB in light of spiral CT results: sensitivity of 59%.

  8. HUPism • There is no diagnostic value in obtaining a KUB on a patient presenting with acute flank pain.

  9. Caveat • Zagoria et al, AJR, 176:1117-1120, 2001: KUB detected 15 of 19 (79%) of calculi > 5mm. • But how many renal stones are > 5mm across? Coll et al, AJR, 178:101-103, 2002: 850 pts with acute flank pain, 172 pts diagnosed with renal stones. Only 34% of stones were > 5 mm across.

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