Assessment of the diagnostic capability of ultrasound in early diagnosis of nephrolithiasis: a feasibility study

CT is the gold standard method for diagnosing kidney and urinary tract stones. This imaging technique delivers radiation dose to patients, which increases the risk of cancer, especially in patients who need frequent assessment. The aim of this study was to compare the diagnostic ability of ultrasound in Iran compared to CT for diagnosing kidney stones in patients with colic pain.

The data of this cross-sectional retrospective study was gathered from the patients who were admitted to a University-affiliated hospital, Shiraz University of Medical Sciences from March 2019 to September 2019 suspected of nephrolithiasis and performed CT were collected along with their ultrasound reports. To compare sonography and CT, sensitivity, specificity, and positive and negative predictive values were calculated and the diagnostic percentage difference between the two modalities was evaluated. The diagnostic efficiency of ultrasound in stones of different sizes and locations was also evaluated.

The sensitivity, specificity, and positive and negative predictive values of ultrasound in the initial diagnosis of stones were 83.47%, 62.15%, 85.94% and 57.58%, respectively. Ultrasound diagnosis was not significantly different from CT p=23 actually ultrasound diagnoses were different from CT in only 2.11% of cases. Ultrasound was the most successful in detecting bladder and urethra stones larger than 10 mm.

The results of this study showed that although ultrasound is less sensitive than CT in the diagnosis of nephrolithiasis, the use of ultrasound could be useful as a primary diagnostic test in patients with suspected nephrolithiasis. The important point is that the strategy of starting the evaluation with ultrasound, and performing additional imaging if necessary, leads to a reduction in the radiation dose of patients with nephrolithiasis. These patients have to do this procedure many times to diagnose and follow up the disease and clearly the offered method leads to reduction of the radiation absorbed dose and the possible effects of radiation, which is in line with the principle of ALARA, the basic principle of radiation protection.