From the Guidelines
Imaging is generally not indicated for uncomplicated pyelonephritis in adults who respond appropriately to antibiotic therapy within 72 hours, but it should be performed in patients with complicated pyelonephritis or those who do not respond to treatment within 72 hours. The decision to perform imaging in patients with pyelonephritis should be based on the presence of complications or risk factors, such as persistent fever or symptoms, immunocompromised status, history of urologic abnormalities or recurrent UTIs, signs of urinary obstruction or abscess, diabetes, elderly age, pregnancy, or male sex 1.
Indications for Imaging
The following are indications for imaging in patients with pyelonephritis:
- Persistent fever or symptoms after 72 hours of appropriate antibiotic therapy
- Immunocompromised patients
- Patients with a history of urologic abnormalities or recurrent UTIs
- Those with signs of urinary obstruction or abscess
- Diabetic patients
- Elderly patients
- Pregnant women
- Men with pyelonephritis
Preferred Imaging Modality
The preferred initial imaging modality is a contrast-enhanced CT scan, which can identify complications such as renal or perinephric abscesses, emphysematous pyelonephritis, and urinary tract obstruction 1. Ultrasound may be used as an alternative in pregnant women or patients with contraindications to CT contrast. MRI can also be considered in these situations.
Importance of Prompt Imaging
Prompt imaging in high-risk scenarios is crucial as it may identify complications requiring additional interventions beyond antibiotics, such as percutaneous drainage of abscesses or relief of urinary obstruction, which can prevent progression to sepsis, renal scarring, or loss of kidney function 1. According to the European Association of Urology guidelines, additional investigations, such as a contrast-enhanced computed tomography scan, should be considered if the patient remains febrile after 72 h of treatment, or immediately if there is a deterioration in clinical status 1.
From the Research
Indications for Imaging in Pyelonephritis
Imaging is not routinely indicated in uncomplicated urinary infections, but it may be necessary in certain situations, including:
- Patients with specific risk factors, such as diabetes, immunocompromised patients, history of stones, or prior renal surgery 2
- Patients not responding to antibiotics 2, 3
- Detecting complications of pyelonephritis, such as emphysematous pyelonephritis, renal abscess, and pyonephrosis 4
- Evaluating patients with concurrent urinary tract obstruction 3
- Pregnant patients with pyelonephritis, who are at significantly elevated risk of severe complications 3
Imaging Modalities
Different imaging modalities can be used to diagnose and assess pyelonephritis, including:
- Computed Tomography (CT) 2, 4, 5
- Ultrasound (US) 5
- Magnetic Resonance Imaging (MRI) 5 Each modality has its own characteristics and can provide valuable information about the structural and functional state of the renal parenchyma and the upper urinary tract.
Timing of Imaging
Imaging should be performed when clinically indicated, such as: