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ultrasound vs CT scan for detecting calculi

Three Part Question

[in patients presenting with loin pain] [is ultrasound better than a CT scan] [ at detecting urinary calculi]?

Clinical Scenario

a 27 male is admitted to the Emergency Department with pain in the right flank. A KUB is taken for an initial diagnosis. The SHO wondered whether a CT scan would be better than an US scan in confirming the presence of a calculus.

Search Strategy

Ovid/medline R 1966- June week4 2005
Embase 1980- week 27 2005
[exp Kidney Diseases/ or exp Hematuria/ or loin or exp Kidney/ or exp Back Pain/] OR [exp Urinary Calculi/ or exp Kidney Diseases/ or exp Kidney Calculi/ or renal] OR
[flank or exp Kidney Diseases/ or exp Flank Pain/ or exp Tomography, X-Ray Computed/ or exp Bacterial Infections/ or exp Pyelonephritis] AND [ or exp Ultrasonography/ or exp ULTRASOUND, HIGH-INTENSITY FOCUSED, TRANSRECTAL/ or exp Ultrasonography, Interventional/] AND [exp Tomography, X-Ray Computed/ or ct] AND [ or exp URETERAL CALCULI/ or exp CALCULI/ or exp URINARY CALCULI/ or exp KIDNEY CALCULI/] limit 8 to (humans and english language)

Search Outcome

13 PAPERS RELEVENT however after discarding foreign language material 8 PAPERS REMAIN RELEVENT of which 4 full text journals are good enough quality to use plus 1 abstract.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
S. Yilmaz, T. Sindel, G. Arslan, C. Ozkaynak, K. Karaali, A. kabaalioglu, E. luleci
Patients with symptoms of renal colic from June 1995 to December 1996clinical trial: comparison of US an CT scan and their ability to diagnose ureteral calculi. 97 pateints were examined with CT scan and US on the same day by 2 radiologists who then reviewed the images. the radiologists were blinded to clinical symptoms and the results of the other imaging modality.number of ureteral stones found. sensitivity and accuracy of US and CT scanning.CT scan detected 60 patients with calculi out of 64 - accuracy 95%. US detected stones in 12 of the 64 patients- accuracy 45%. CT detected a total of 16 renal stones, US deteced 5 renal stones . CT showed 94% sensitivity and 97% specifictiy compared to US which showed 19% sensitivity and 97% specitivity. CT had a 98% positive predicted value and a 89% negative predictive value. US had a 92% positive predictive value and a 38% negative predictive value.The determination of true negative and true positive cases was based on the patients' observation as to whether they recovered a stone or not. Small stones could have been missed by the patients hence, the number of false negative cases will have been underestimated and the false positive cases overestimated.
T. Ripolles, M. Agramunt, J. Errando, M.J. Martinez, B. Coronel, M. Morales
56 Emergeny Room patients with acute flank painClinical Trial: a comparison of the sensitivity and specificity of ultrasound and nonenhanced CT for the diagnosis of ureteral colic.number of lithiasis detected by each modality and their sensitivity and specificityultrasound detected calculi in 44 of the 56 patients with confirmed renal colic- sensitivity 79%, CT detected calculi in 52 patients out of 56- sensitivity 93%. statistically significant differences found in sensitivity using Chi-squared test (p<0.05). specificity 100% for both modalities.Only patients admitted between 8am and 3pm were used in the study. Also true positive cases comprised 84% of the study group due to good patient selection in the Emergency Department. There were also relatively few nonurological abnormalities (3%) and so the US may have been overestimated.
K. Fowler, J. Locken, J. Duchesne, M. Williamson
New Mexico
Patients who underwent CT and US at the department between December 1997 and July 2000Clinical Trial: a comparison of the sensitivity and specificity of US for detecting renal calculi in comparison with CT scanning. 123 patients underwent US and CT scanning within 30 days of one another. The results were reviewed in a blinded retrospective manner by 2 staff radiologists who specialize in imaging, providing a consensus interpretation.number of calculi detected by ultrasound and its sensitivity, specificaity and accuracy with CT as a reference standard.US demonstrated 24 of the 101 renal calculi identified on CT images- sensitivity 24% (95% CI:18%,39%) specificty 90% (95% CI: 85%,94%). Accuracy of ultrasound detecting individual renal claculi was 54% (95% CI: 47%, 61%) Accuracy of US detecting any renal calculi in a given patient was 77%. ultrasound identified 7 of the 13 patients with multiple calculiThere was a delay between the performance of US and CT scan. The mean time elapsed between examinations was less than a week,however it would have been optimal to peform the two imaging techniques one after the other to minimise the chances of calculi being passed before the imaging is performed. Also the imaging interpretation was given as a consensus of the 2 radoilogists views. There may have been experience bias.
M. Patalas, A. Farkas, D. Fisher, I. Zaghal, I. Hadas-halpern
Patients with suspected renal colic in the Emergency Department over a 9 month period.Clinical Trial: to compare the accuracy of non-contrast spiral CT with ultrasound for the diagnosis of ureteral calculi in the evaluation of 62 consecutive patients with acute flank pain. US was performed followed by CT scan within 4hours of admission. The examinations were performed and reviewed by senior radiologists. The two sets of studies were reviewed by independent radiologists who were blinded to the patients identity.number of ureterolithiasis found by each imaging technique. comparison of the sensitivity, specificity and accuracy of US and CT in detecting calculi.US showed calculi in 40 of the 43 patients with confirmed ureteral calculi- sensitivity 93%, specificity 95%, positive predictive value 98%, negative predictive value 85%. CT detected calculi in 39 of the 43 patients- sensitivity 91%, specificity 95%, postive predicted value 98% and negative predictive value 82%.All the patients had some degree of uterohydronephrosis allowing the US to follow the ureter to the level of the stone and examine the exact nature of the obstruction. This may not have been possible if there was no hydronephrosis and so the accuracy of US in this study may have been overestimated.
D.H Sheafor, B.S Hertzberg, K.S Freed, B.A Carroll, M.T Keogan, E.K. Paulson, D.M. Delong, R. Nelson
Patients undergoing nonenhanced CT scan and ultrasound over a time span of 9 monthsClinical Trial: a comparison of nonenhanced CTand US for the depiction of urolithiasis. 45 patients attending the ED underwent CT scan and US with clinical,surgical and imaging follow up.number of calculi detected by US and CT and their respective sensitivities and specificities.CT depicted 22 of the 23 ureteral calculi- sensitivity 96%. US detected 14 out of the 23 calculi- sensitivity 61%. differences in sensitivity statistically significant P=0.02 using McNemar test. specifictiy for each modality 100%FULL TEXT NOT YET AVAILABLE.


All papers found CT scan to be superior in detecting calculi in patients with loin pain. Some studies found US to be of limited value and that CT should be considered the standard. Other studies however, found that in clinical practice plain film plus US had a similar patient outcome than CT,as the stones missed by US are usually small and should pass spontaneously. Perhaps a CT scan is superior, however, the cost and the risks of radiation along with the time it takes to perform makes it unpractical in the emergency department.

Clinical Bottom Line

CT scan is shown to be a more accurate mode of imaging for detect urinary calculi. However, US should be performed first and CT should be reserved for those patients with clinical symptoms of major colic who have had a negative US.


  1. S. Yilmaz, T. Sindel, G. Arslan, C. Ozkaynak, K. Karaali, A. kabaalioglu, E. luleci Renal colic: Comparison of spiral CT, US, and IVU in the detection of ureteral calculi European Radiology 1998;8:212-217
  2. T. Ripolles, M. Agramunt, J. Errando, M.J. Martinez, B. Coronel, M. Morales suspected ureteral colic: plain film and sonography vs unenhanced helical CT. A prospective study in 66 patients. European Radiology 2004;14:129-136
  3. K. Fowler, J. Locken, J. Duchesne, M. Williamson US for detecting renal calculi with nonenhanced CT as a reference standard. Radiology 2002;222:109-113
  4. M. Patalas, A. Farkas, D. Fisher, I. Zaghal, I. Hadas-Halpern Ultrasound vs CT for the detection of ureteric stones in patients with renal colic The British Institute of Radiology 2001;74:901-904
  5. D.H Sheafor, B.S Hertzberg, K.S Freed, B.A Carroll, M.T Keogan, E.K. Paulson, D.M. Delong, R. Nelson Non enhanced CT and US in the emergeny evaluation of patients with renal colic: a prospective comparison. Radiology Dec 2000;217(3):792-7