2. A Normal Renal Ultrasound IS helpful

Take Home:  Sometimes a negative study is harder to explain to patients than positive studies. These two studies give me a chance to say “Great! Your chance of passing this kidney stone on your own is almost 100%” if I get the Normal renal US.

These two studies are a retrospective analysis from 2010 followed by a prospective study from Jan 2015 that give us an idea of what the results of the US mean. 



The utility of renal ultrasonography in the diagnosis of renal colic in emergency department patients

– Canadian Journal of EM 2010 

http://www.emergencyultrasoundteaching.com/assets/articles/Renal_2010_Edmonds_CJEM.pdf

 

Study: Retrospective review of US ordered in the ED for renal colic. Classified into 4 categories.

  1. Normal Renal US
  2. Suggestive Renal US: hydronephrosis, perinephric fluid or periureteral stranding, intrarenal stones, or an abnormal or absent ureteric jet was present.
  3. Stone Visualized
  4. Other pathology visualized

 

Outcome: Requirement for urologic procedure in the next 3, 10, 14, or 90 days

 

Results: Of 817 Renal US obtained

% of total US % with intervention in 90 days
Normal US 43%

                 0.6%

Suggestive US 22%                  6.8%
Stone Visulaized 30%                  6.2%


Now, the prospective validation:

 

Normal renal sonogram identifies renal colic patients at low risk for urologic intervention: a prospective cohort study

– Canadian J Med Jan 2015

 http://journals.cambridge.org/download.php?file=%2FCEM%2FCEM17_01%2FS1481803514000128a.pdf&code=02659c3419bea7c4b810d4d41529542f

Study: Prospective observational study

Population: ED patients with clinically suspected renal colic.

Intervention (same as above):

  1. Normal Renal US
  2. Suggestive Renal US: hydronephrosis, perinephric fluid or periureteral stranding, intrarenal stones, or an abnormal or absent ureteric jet was present.
  3. Stone Visualized
  4. Other pathology visualized

Primary Outcome: Number of patients requiring a urologic procedure within 90 days.

Results: 341 patients enrolled who had US for suspected renal colic.

% of total US % with intervention in 90 days
Normal US 30%

                 0%

Suggestive US 27%                  10%
Stone Visulaized 40%                  25%

Conclusions: If you get a normal renal US, the chances of requiring urologic intervention in the next 90 days is extremely low.

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