Diagnostic accuracy of ultrasonography compared to unenhanced CT for stone and obstruction in patients with renal failure

Abstract

BackgroundTo determine accuracy of ultrasound (US) kidney, ureter and bladder (KUB) compared to un-enhanced helical CT (UHCT) in patients with renal failure in the diagnosis of stone and obstruction.MethodsThis is a case controlled study conducted in the period from June 2000 to July 2003 at a university hospital. All patients had both US and UHCT scan. Patients with serum creatinine ≥ 1.8 mg/dl were included in the study. Only direct visualization of stone was considered as confirmatory. In both the studies, UHCT and US, presence of stone and obstruction were noted. The relevant biochemicals, radiological and clinical records of all the patients were analyzed. Data was analyzed using commercially available software.ResultsDuring the period of study 864 patients had UHCT for evaluation of the urinary tract in patients presenting with flank pain. Out of these 34 patients had both UHCT and US done within a span of one day and had serum creatinine of ≥1.8 mg/dl. Mean age was 48 ±15.8 years and 59% of patients were males. UHCT identified renal stones in 21 (62%), whereas 17 of these were identified on US, with a sensitivity of 81%. Of the four patients with renal stones missed on US, three were identified on plain x-ray; the mean size of stones missed was 6.3 mm. Of the 22 (65%) patients with ureteric stone on UHCT, US could only identify 10; a further 7 were identified on x-ray KUB, giving a sensitivity of 45% (US alone) and 77% (US with x-ray KUB).ConclusionsUS is sensitive and specific for renal stones, 81% and 100% and for hydronephrosis, 93% and 100%, respectively. Its sensitivity to pick ureteric stone (46%) and to identify hydroureter (50%) is low. Addition of x-ray KUB abdomen increases the sensitivity for ureteric stones to 77%.

Accuracy of sonography for detecting renal stone: Comparison with CT

“…Several recent studies have investigated the value of sonography for detecting renal stones using CT as the reference standard. 7,11,12 Our data indicate that sonography is of limited value for diagnosing renal stone disease. A major reason for this is the difficulty of examining the left kidney, and, accordingly, the sensitivity of sonography for detecting renal stones in the left kidney was lower than that for the right kidney.…”

“…5 CT demonstrates renal stones more accurately than plain radiography, sonography, nephrotomography, and excretory urography. [6][7][8][9][10] Currently, CT is the preferred modality for evaluating patients with urinary colic, 11,12 but sonogra- phy is the modality of choice for cases in which exposure to ionizing radiation is of particular concern (eg, pregnant women and pediatric patients).…”

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“…A study by Ather, et al [16] has determined the accuracy of ultrasonography, as compared un-enhanced helical among patients having renal failure in the obstruction and stone diagnosis. Ultrasound has many different intrinsic advantages, which comprise of universal availability, scarcity of radiations, non-invasive, and inexpensive.…”

Non-contrast CT in the Evaluation of Urinary Tract Stone Obstruction and Haematuria

“…It is particularly useful in the diagnosis of ureteral stones (Figures 1 and 2) with sensitivity of 95-98% and speciicity of 96-98% [8,9]. It is of particular value in patients with renal failure, which precludes use of intravenous contrast, and ultrasound has limited value [10]. The sensitivity of ultrasound in the evaluation of ureteral stones when compared with CT KUB is only 46% and for hydroureter in half of the cases.…”