CT Abdomen Without Contrast for Hematuria and Lower Back Pain
Yes, a patient with hematuria and lower back pain should get a non-contrast CT of the abdomen and pelvis, as this is the optimal initial imaging modality for suspected urolithiasis, which is the most likely diagnosis in this clinical presentation. 1
Primary Diagnostic Rationale
Non-contrast CT abdomen and pelvis is the gold standard for evaluating suspected kidney stones, which commonly present with both hematuria and flank/back pain:
- Non-contrast CT has superior sensitivity (>95%) and specificity (>95%) for detecting urinary calculi compared to all other imaging modalities 2, 3
- The absence of IV contrast allows optimal visualization of stones of all compositions, which would otherwise be obscured by contrast material 1
- This protocol identifies hydronephrosis, stone size, location, and burden—all critical factors for treatment planning 1, 4
When Non-Contrast CT is Most Appropriate
The clinical presentation of hematuria plus lower back pain strongly suggests urolithiasis as the primary concern:
- Hematuria has 77% sensitivity for urolithiasis overall, and 85% sensitivity specifically for ureteral stones 3
- In patients with flank pain and hematuria, non-contrast CT identifies stones in approximately 64% of cases 3
- The combination of moderate-to-severe hydronephrosis on ultrasound (if performed first) plus hematuria increases the positive predictive value to 88% for ureteral stones 1, 4
Important Clinical Caveat
The absence of hematuria does NOT exclude urolithiasis—approximately 23% of patients with confirmed stones on CT have no hematuria 3. Therefore, imaging should not be withheld based on urinalysis alone.
Alternative Diagnoses Requiring Different Imaging
If urinalysis is negative for hematuria and there is no history of kidney stones, consider CT abdomen and pelvis with IV contrast instead:
- Contrast-enhanced CT identifies clinically significant non-urological diagnoses in 15% of patients with flank/back pain and negative urinalysis 5
- These alternative diagnoses include appendicitis, vascular pathology (aortic aneurysm in patients >60 years), gynecological pathology, or other intra-abdominal processes 5
Radiation Considerations
For patients with recurrent stones or young patients requiring repeated imaging:
- Use low-dose CT protocols when available, reducing radiation to <3 mSv 4
- Consider starting with ultrasound in low-risk presentations, reserving CT for when ultrasound is nondiagnostic 4
- In pregnant patients, ultrasound is first-line (appropriateness rating 8), with MRI as second-line if inconclusive 4
Comprehensive Urography (CTU) is NOT First-Line Here
While CT urography (CTU) with contrast is the preferred modality for evaluating microscopic hematuria without pain (to detect urothelial malignancies), it is not the optimal choice for acute flank pain with hematuria:
- CTU has 96% sensitivity and 99% specificity for urothelial malignancy 1
- However, for suspected acute stone disease, the non-contrast phase alone provides all necessary diagnostic information 1
- CTU should be reserved for patients requiring comprehensive evaluation of the entire urinary tract when malignancy is suspected 1, 6