From the Guidelines
In the management of complicated UTI, a physician would request a KUB ultrasound despite having a CT stonogram done primarily to monitor treatment response, assess for complications such as hydronephrosis or renal abscesses, and evaluate renal perfusion without the need for radiation exposure. This approach is supported by the American College of Radiology's appropriateness criteria for recurrent lower urinary tract infections in females, which suggests that imaging such as CTU or MRU is appropriate for evaluating recurrent complicated lower UTIs, but does not preclude the use of ultrasound for specific indications 1.
Key Considerations
- Ultrasound offers real-time imaging without radiation exposure, making it suitable for repeated evaluations or monitoring treatment response over time.
- It is particularly useful for assessing hydronephrosis, renal abscesses, and fluid collections that may develop or change during treatment.
- Ultrasound can characterize soft tissue abnormalities and provide detailed blood flow information through Doppler imaging, aiding in the evaluation of renal perfusion in cases of pyelonephritis.
- For patients with contraindications to CT contrast, such as renal impairment or allergies, and for vulnerable populations like pregnant women or children, ultrasound is a preferred alternative 1.
Clinical Application
In clinical practice, the decision to use a KUB ultrasound in addition to a CT stonogram in the management of complicated UTI should be based on the individual patient's needs and the specific clinical scenario. The ability of ultrasound to provide complementary information to CT imaging, without the risks associated with radiation, makes it a valuable tool in the ongoing management of these patients. As noted in the guidelines for recurrent lower urinary tract infections, the choice of imaging should be tailored to the patient's condition and the clinical question being addressed 1.
From the Research
Reasons for Requesting a KUB Ultrasound
Despite having a CT stonogram done, a physician may request a KUB (Kidneys, Ureters, Bladder) ultrasound in the management of complicated UTI for the following reasons:
- To evaluate the severity of hydronephrosis, as ultrasound is a useful modality for detecting hydronephrosis and its severity 2
- To assess for any changes in the renal collecting system, as hydronephrosis can be diagnosed using various modalities, including sonography 3
- To guide treatment decisions, as the presence and severity of hydronephrosis can impact treatment outcomes 4, 3
- To monitor for potential complications, such as acute kidney injury and permanent nephron loss, which can occur if hydronephrosis is not corrected 4
Comparison of Imaging Modalities
While CT stonogram is a valuable tool for evaluating urinary tract infections, ultrasound has its own advantages, including:
- Being a non-invasive and relatively low-cost modality 2
- Providing real-time imaging, which can be useful for guiding procedures or monitoring changes in the renal collecting system 2
- Being a useful adjunct to CT stonogram, as it can provide additional information on the severity of hydronephrosis and guide treatment decisions 2