What imaging studies should be performed to evaluate for anatomical abnormalities in a patient with recurrent urinary tract infections?

Imaging for Recurrent Urinary Tract Infections

Direct Recommendation

For uncomplicated recurrent UTIs in otherwise healthy women, imaging is NOT routinely indicated and should be avoided due to low diagnostic yield. 1, 2, 3 However, CT Urography (CTU) is the primary imaging test when evaluation is warranted for complicated recurrent UTIs, including patients who fail conventional therapy, have frequent relapses within 2 weeks of treatment, or possess known underlying risk factors. 1, 2

When Imaging Should NOT Be Performed

• Routine imaging is not appropriate for uncomplicated recurrent UTIs in otherwise healthy premenopausal women without known urological abnormalities. 2, 3
• The American College of Radiology explicitly states that most women with uncomplicated recurrent UTIs have normal urinary tracts, making routine imaging low-yield. 2
• Cystoscopy and upper tract imaging should NOT be routinely obtained in otherwise healthy women with recurrent uncomplicated UTI. 3

When Imaging IS Indicated (Complicated UTI Scenarios)

Imaging should be pursued in the following specific circumstances:

• Nonresponse to conventional antibiotic therapy 2
• Frequent reinfections or relapses, particularly infections recurring within 2 weeks of completing treatment 2
• Known underlying risk factors including structural abnormalities, immunosuppression, diabetes, pregnancy, or anatomic urinary tract abnormalities 2, 3
• Suspected anatomic causes of bacterial persistence such as calculi, foreign bodies, urethral or bladder diverticula, infected urachal cyst, or postoperative changes 2

Primary Imaging Modality: CT Urography (CTU)

CTU is the gold standard imaging test for evaluating complicated recurrent UTIs. 1, 2

Technical Components and Advantages:

• CTU includes three phases: unenhanced, nephrographic phase, and excretory phase images, providing comprehensive anatomic depiction of kidneys, intrarenal collecting systems, ureters, and bladder. 1, 2
• Excellent sensitivity and specificity for identifying renal and urothelial lesions, congenital anomalies, and obstruction 1, 2
• Diuretic administration prior to the excretory phase can augment urinary tract distention and opacification. 1
• Superior to standard contrast-enhanced CT of abdomen/pelvis, which is not optimally tailored for urothelial evaluation and lacks the unenhanced component needed for calculi detection. 1

Alternative Imaging Options

MR Urography (MRU):

• MRU is the preferred alternative to CTU in patients with contraindications to CT or iodinated contrast. 2
• Provides more functional information than CT and is useful for evaluating suspected urinary tract obstruction and congenital anomalies. 2
• Has supplanted intravenous urography (IVU) at most institutions. 2

Ultrasound of Kidneys, Bladder, and Retroperitoneum:

• May be useful as an initial screening tool in complicated cases, particularly for diagnosing certain conditions like hydronephrosis or large calculi. 2
• However, ultrasound alone has significant limitations with sensitivity of only 66.7% and specificity of 37.5% for detecting urinary tract anomalies. 4
• Ultrasound is inadequate as a standalone test for comprehensive evaluation of recurrent UTIs. 1, 4

CT Pelvis with Bladder Contrast (CT Cystography):

• Useful specifically for diagnosing bladder fistulas and leaks, particularly colovesical fistulas from sigmoid diverticular disease. 1, 2
• Has supplanted fluoroscopic cystography for evaluation of traumatic bladder injuries. 1, 2

Obsolete Imaging Techniques to Avoid

• Intravenous urography (IVU) is no longer recommended and has been replaced by CTU/MRU at most institutions. 2
• Fluoroscopic cystography has been supplanted by CT cystography. 1
• Double-balloon urethrography for urethral diverticula has been replaced by MRI. 1
• Contrast enema is generally not useful, as CT has higher detection rates for enterovesical fistulas. 1

Role of Cystoscopy

• Cystoscopy should be considered in females with recurrent complicated UTIs and known structural abnormalities, allowing direct visualization of anatomic issues like ureteroceles and potential obstruction. 1, 2
• Not routinely indicated for uncomplicated recurrent UTIs. 3

Critical Clinical Pitfalls

• Do not order standard contrast-enhanced CT abdomen/pelvis instead of CTU—it lacks the unenhanced and excretory phases necessary for comprehensive urinary tract evaluation. 1
• Avoid classifying patients as "complicated" without true structural/functional abnormalities, immunosuppression, or pregnancy, as this leads to unnecessary imaging and broad-spectrum antibiotics. 3
• Do not image for asymptomatic bacteriuria in otherwise healthy women. 3
• In children, despite normal renal-bladder ultrasound, 24% may still have dilating vesicoureteral reflux, highlighting the limitations of ultrasound alone. 5, 6

Algorithmic Approach

1. First, determine if the UTI is truly "complicated" by assessing for nonresponse to therapy, rapid relapses (<2 weeks), or known risk factors. 2, 3
2. If uncomplicated recurrent UTI in healthy woman: NO imaging. 2, 3
3. If complicated UTI: Order CTU as first-line imaging. 1, 2
4. If contraindication to CT/contrast exists: Order MRU instead. 2
5. If specific concern for bladder fistula: Add CT cystography. 1, 2
6. Consider cystoscopy if structural abnormality suspected or identified on imaging. 1, 2