Article: Sensitivity of Emergency Bedside Ultrasound to Detect Hydronephrosis in Patient with Computed Tomography-proven stones
Riddell J, Case A, Wopat R, Beckham S, Lucas M, McClung CD, Swadron S. Sensitivity of emergency bedside ultrasound to detect hydronephrosis in patients with computed tomography-proven stones. West J Emerg Med. 2014 Feb;15(1):96-100. doi: 10.5811/westjem.2013.9.15874. PMID: 24578772; PMCID: PMC3935794.
Objective: To assess trends in sensitivity of EMBU when compared to CT scan of unilateral hydronephrosis in evaluation for stone size and number.
Design: Structured, explicit, blinded retrospective chart review
Inclusion Criteria: Adults (³18 years) from July 1, 2009 through January 31 2010 with diagnosis of renal colic by using ICD-9 codes of kidney calculus, ureter calculus, urinary calculus unspecified, bladder calculus, ureteral calculus, and renal colic. Of those patients, those who had CT read by an attending radiologist diagnosis of renal calculus who had EMBU performed by Emergency Medicine Physician during that same visit. Only patients with CT and EMBU findings of renal calculi from the same visit were included.
Exclusion Criteria: No other exclusionary criteria aside from that which is described above.
Methods: Adults described above were selected. Ultrasound findings were positive if hydronephrosis was recorded (mild, moderate, severe, small, stage I, stage II, stage III) or any documentation of sonographically evident stones. The number of stones were also recorded by attending radiology CT reads. “Several”, “few”, and “multiple” were interpreted as >=3 stones. Two investigators were blinded to the study hypothesis as abstractors to independently review charts. Final CT report was compared to results of the EMBU demonstrating hydronephrosis or sonographically evident stones.
Results: 511 patients during this 6-month study period came with the diagnosis of renal colic with 198 of which having CT proven stones. 125 patients had both CT proven stones and sonographic documentation of stones or hydronephrosis. The sensitivity of ultrasound for detection of hydronephrosis was 78.4% (95% CI = 70.2-85.3); the sensitivity of ultrasound for either hydronephrosis or visualized stones was 82.4% (95% CI = 75.6, 89.2). There was a statistically significant difference in detecting hydronephrosis in a patient with a stone greater than or equal to 6 mm with a sensitivity 90% (95% CI = 82-98%) compared to stones less than 6 mm (sensitivity 75% (95% CI = 65-86%)). For individuals with 3 or more stones, sensitivity was 100% (95% CI 63-100%); sensitivity with 2 stones was 94% (95% CI 82-100), and with one stone was 75% (95% CI = 65-83). Interestingly, when combining microscopic hematuria with positive
EMBU; sensitivity improved based on stone size from 89% (95% CI 78-95%) in patients with stones <6 mm to 100% (95% CI 93-100) in patients with stones ³6 mm.
Takeaway: Ultrasound has been used in diagnosis and management of renal stones and proves advantageous over CT when considering ionizing radiation, time and resource utilization and cost. In this study, 100% of patients with stones greater than 6 mm were identified by either hematuria or EMBU findings. This study has also show that the sensitivity of EMBU improves with increasing stone size and number. Given that stones ³6 mm are unlikely to pass on their own, this diagnostic tool can help EM providers to select patients that require treatment and those with a safe disposition home. This is the first study to use stone size in correlation to outcome.
Author: Katey Cohen, MS4