What is the evidence for renal ultrasound in acute pyelonephritis, and are there Australian guidelines?

From the Guidelines

Renal ultrasound is not routinely recommended for uncomplicated acute pyelonephritis in adults, but it should be performed in specific clinical scenarios, such as patients with severe illness, those who fail to respond to appropriate antibiotic therapy within 72 hours, recurrent infections, suspected anatomical abnormalities, history of urolithiasis, or immunocompromised status, as suggested by the European Association of Urology guidelines 1. The use of renal ultrasound in pyelonephritis is guided by the principle of selective imaging, reserving it for cases where complications are suspected or the patient's condition warrants further evaluation.

• The European Association of Urology guidelines recommend evaluation of the upper urinary tract via ultrasound to rule out urinary tract obstruction or renal stone disease in patients with a history of urolithiasis, renal function disturbances, or a high urine pH 1.
• Australian guidelines, although not explicitly stated in the provided evidence, are expected to align with international consensus, emphasizing the importance of clinical judgment in deciding when to use imaging in the management of pyelonephritis.
• The American College of Radiology Appropriateness Criteria also support the selective use of imaging, suggesting that CT abdomen and pelvis with IV contrast is appropriate for complicated cases, while ultrasound may be considered for initial evaluation in certain scenarios 1. Key points to consider include:
• The majority of uncomplicated pyelonephritis cases can be managed with empiric antibiotic therapy without the need for routine imaging.
• Specific patient populations, such as children, pregnant women, elderly patients, and those with diabetes or immunosuppression, may have lower thresholds for imaging due to increased risk of complications.
• When ultrasound is performed and shows concerning findings, further imaging with CT or MRI may be warranted to guide management and intervention. The rationale behind selective imaging is to balance the benefits of early detection of complications with the potential drawbacks of unnecessary imaging, including increased healthcare costs and resource utilization, without changing the management in most cases 1.

From the Research

Renal Ultrasound in Pyelonephritis

• The use of renal ultrasound in adult patients with acute pyelonephritis (APN) has been evaluated in several studies 2, 3, 4.
• A study published in 2007 found that the low incidence of ultrasonographic findings does not justify the practice of renal US to every patient with APN, but it may be useful in patients with persistent fever, antecedents of anomalies of the urinary tract, antecedents of renal lithiasis, pregnancy, atypical clinic or diabetes mellitus 2.
• A narrative review published in 2024 recommends not performing diagnostic imaging unless a complicated APN is suspected or the infection affects high-risk patients, and highlights the value of contrast-enhanced ultrasound (CEUS) in the diagnosis and follow-up of APN 3.
• Another study published in 2006 reviews the importance of renal sonography in evaluating renal infections, including pyelonephritis, and providing valuable information for appropriate management 4.

Australian Guidelines/Evidence

• There is no specific evidence provided on Australian guidelines for the use of renal ultrasound in pyelonephritis.
• However, a study published in 2011 correlates clinical parameters with radiological severity of CT diagnosed acute pyelonephritis (APN) and renal abscesses, and may be relevant to informing clinical practice in Australia 5.
• Another study published in 2014 reviews the current clinical management of renal and perinephric abscesses, which may be relevant to Australian clinical practice 6.