Acute pyelonephritis: comparison of diagnosis with computed tomography and contrast-enhanced ultrasonography

To assess the value of contrast-enhanced ultrasonography (US) with the contrast pulse-sequence (CPS) technique for detecting renal parenchymal changes in acute pyelonephritis (APN), compared with contrast-enhanced computed tomography (CT) as the reference standard.

We examined 100 patients (82 women, 18 men; mean age 30.2 years, range 18-67); children (those aged <18 years) were excluded from the study. All patients had clinical symptoms suggestive of APN. For the US a Sequoia 512 (Acuson, Mountain View, CA, USA) unit including Cadence CPS technology, with a 6C2 probe, was used. A bolus of a 2.4-mL US contrast agent SonoVue (Bracco, Milan, Italy) was injected. For CT a multislice 16-row unit was used (Sensation 16, Siemens, Erlangen, Germany), at a table speed of 2.5 mm/s and a slice thickness of 3 mm; 100 mL of intravenous iodinated contrast agent (flow 3 mL/s) was injected.

On contrast CT, 84 patients (84%) had renal parenchymal changes suggestive of APN; on contrast US, 82 of the 84 (98%) showed renal parenchymal changes, and APN was correctly diagnosed. Seventy-six patients (90%) had unilateral and eight (10%) had bilateral APN, and in two (2%) with APN the diagnosis could not be confirmed by US/CPS (false-negative). No false-positive findings were detected on US/CPS, which had a sensitivity of 98%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 89%.

CPS/US is accurate for detecting parenchymal changes in APN; it is very sensitive and specific, and allows small renal parenchymal changes to be detected with no radiation exposure.