CT Abdomen Without Contrast for Hematuria and Lower Back Pain

Primary Diagnostic Rationale

The American College of Radiology recommends non-contrast CT abdomen and pelvis as the gold standard for evaluating suspected kidney stones, which commonly present with both hematuria and flank/back pain, due to its superior sensitivity (>95%) and specificity (>95%) for detecting urinary calculi 1, 2
The absence of IV contrast allows optimal visualization of stones of all compositions, which would otherwise be obscured by contrast material 1, 2
This protocol identifies hydronephrosis, stone size, location, and burden—all critical factors for treatment planning 1, 2, 4

The combination of moderate-to-severe hydronephrosis on ultrasound plus hematuria increases the positive predictive value to 88% for ureteral stones 1, 4

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, gynecological pathology, or other intra-abdominal processes 5

The American College of Radiology suggests using 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, with MRI as second-line if inconclusive 4

CTU has 96% sensitivity and 99% specificity for urothelial malignancy, but is not the optimal choice for acute flank pain with hematuria 6
For suspected acute stone disease, the non-contrast phase alone provides all necessary diagnostic information 1, 2