When should an abdominal ultrasound (abdo US) be performed for recurring urinary tract infections (UTIs)?

When to Get Abdominal Ultrasound for Recurrent Urinary Tract Infections

Abdominal ultrasound is not routinely indicated for uncomplicated recurrent UTIs but should be performed for complicated UTIs, including cases with nonresponse to therapy, frequent reinfections, or known risk factors for urinary tract abnormalities. 1

Uncomplicated Recurrent UTIs

• Imaging studies, including abdominal ultrasound, are usually not appropriate for recurrent uncomplicated lower UTIs in females with no known underlying risk factors 2
• Most women with recurrent uncomplicated UTIs have normal urinary tracts and do not require routine imaging 2
• The yield of finding clinically significant anatomic abnormalities is low in patients with uncomplicated recurrent UTIs 2

Complicated Recurrent UTIs: When to Get Abdominal Ultrasound

Abdominal ultrasound should be considered in the following scenarios:

• Patients who are nonresponders to conventional antibiotic therapy 1
• Patients who develop frequent reinfections or relapses, particularly infections recurring within 2 weeks of treatment 1
• Patients with known underlying risk factors for complicated UTIs 2, 1
• Prior to pregnancy in women with recurrent UTIs to evaluate for hydronephrosis and risk factors for recurrent infection 2

Role of Ultrasound in Complicated UTIs

• Ultrasound is a useful initial screening tool for obstructive uropathy and for postvoid residual volume determination to detect incomplete bladder emptying 2
• It can detect hydronephrosis as an indication of obstruction, although it may not yield a specific etiology 2
• Ultrasound can identify renal abscesses, perinephric collections, and bladder diverticula 2
• While ultrasound can detect renal stones, it is generally less sensitive than CT for this purpose 2

Limitations of Ultrasound

• Ultrasound alone has limited value in diagnosing all urinary tract anomalies, with a reported sensitivity of 66.7% and specificity of 37.5% in some studies 3
• For comprehensive evaluation of complicated UTIs, CT Urography (CTU) or MR Urography (MRU) may be more appropriate as they provide more detailed anatomic depiction of the urinary tract 1

Alternative Imaging Modalities for Complicated UTIs

• CT Urography (CTU) is recommended as the primary test for evaluation of recurrent complicated UTIs by the American College of Radiology 1
• MR Urography (MRU) is an alternative to CTU in patients with contraindications to CT or iodinated contrast 1
• These modalities have largely supplanted older techniques such as intravenous urography (IVU) 2

Special Populations

• In men with UTIs (which are generally considered complicated), diagnostic imaging should be started early to rule out complicating factors in the urinary tract 4, 5
• In patients with inflammatory bowel conditions like Crohn's disease who have recurrent UTIs, abdominal ultrasound has good specificity and sensitivity for detecting urologic complications 6

Remember that while imaging is not routinely indicated for uncomplicated recurrent UTIs, clinical judgment should guide the decision to perform imaging studies based on the presence of complicating factors or treatment failure.