Appropriate Imaging Modalities in the Emergency Department for Assessment of Renal Stones

Abstract

Introduction:

Urolithiasis prevalence is approximately 15-20%, the third most common urological presentation to emergency departments (ED). In the ED, renal stones are usually diagnosed by clinical presentation, but imaging modalities play a role in confirmation and exclusion of hydronephrosis. 85% of stones are calcium oxalate/calcium phosphate, which are radio opaque, and 15% are radiolucent uric acid or cysteine stones. Non-contrast CT scans have 95% and 97% sensitivity and specificity rates, while x-rays have 57% and 76% respectively. In Wexford General Hospital, radiology prefers plain film x-rays prior to CT scans in assessing kidney stones.

Method:

The aim of this study was to assess the sensitivity of x-rays in patients undergoing low dose non-contrast CT for kidney stones and to apply this information to clinical practice. A retrospective audit was conducted using NIMIS/PACS from December 1, 2021-March 31,2022. All patients who underwent CT KUBS for evaluation of renal stones were included, and CT KUB findings were compared with initial x-ray findings.

Results:

A CT KUB was performed on 56 patients to assess renal stones, and 29 patients had renal stones. Among 29 patients, 21 had x-rays and CT scans performed, and 12 had x-ray findings that indicated renal stones, indicating 57% sensitivity. The study found 36 patients had x-rays for renal stones, but no CT scan was scheduled for 15 patients who might have undiagnosed radiolucent stones.

Conclusion:

Radiological imaging plays a central role in the management of suspected renal stones. CT KUB is a useful tool for evaluating patients with radio-opaque kidney stones as well as detecting radiolucent stones and renal pathologies that can be missed with plain radiographs. Low-dose CT KUB is recommended as a first-line investigation for renal stone patients to reduce radiation risks and unnecessary abdominal x-rays while assisting clinicians in accurately diagnosing patients and excluding other possible causes.