What type of computed tomography (CT) scan is recommended for a patient with suspected liver and kidney stones, considering potential pre-existing kidney disease?

CT Imaging for Kidney and Liver Stones

For kidney stones, order a non-contrast CT abdomen and pelvis, which is the gold standard with 97% sensitivity; for liver stones (choledocholithiasis or intrahepatic stones), order a multiphase CT abdomen with IV contrast, though note that "liver stones" are extremely rare and you likely mean gallstones or bile duct stones. 1, 2

Kidney Stone Imaging

Primary Recommendation

• Non-contrast CT (NCCT) abdomen and pelvis is the reference standard for kidney stone evaluation, with sensitivity as high as 97% and specificity of 95% 2
• Virtually all renal calculi are radiopaque on CT, allowing accurate detection of even small stones without IV contrast 2
• Use low-dose CT protocols (<3 mSv) to reduce radiation exposure while maintaining excellent diagnostic performance (pooled sensitivity 97%, specificity 95%) 2, 3

Technical Specifications

• Request thin (1-1.5 mm) axial slice images for optimal stone detection 2
• Stone location and size are accurately depicted, which is crucial for determining management as more proximal and larger stones require intervention 2
• Coronal reformations, bone window settings, and magnified views improve accuracy of stone measurements 2

Critical Pitfall to Avoid

• Never order CT with IV contrast as first-line imaging for kidney stones, as the enhancing renal parenchyma obscures stones within the collecting system 1, 2
• If contrast-enhanced CT has already been performed, it can still detect larger stones (≥6 mm) with approximately 98% accuracy, but this is suboptimal 2

Special Consideration for Pre-existing Kidney Disease

• In patients with moderate to severe hydronephrosis on ultrasound and moderate or high risk of ureteric calculi, ultrasound may provide sufficient diagnostic certainty without requiring CT 2
• If stone size and location are needed to plan surgical management in these patients, use low-dose CT protocols 2
• For patients with recurrent stone disease, limit the CT scan to the area of interest or use ultra-low-dose protocols to reduce cumulative radiation exposure 2

Liver Stone Imaging (If Truly Indicated)

Important Clarification

• True "liver stones" (intrahepatic lithiasis) are extremely rare in Western populations
• If you mean bile duct stones (choledocholithiasis), these require different imaging
• If you mean liver lesions, see below

For Liver Lesion Characterization

• Order CT abdomen with IV contrast multiphase (triple-phase) if evaluating an indeterminate liver lesion 4
• The multiphase approach includes arterial, portal venous, and delayed phases to characterize enhancement patterns 4
• For patients with chronic liver disease, multiphase CT is appropriate per LI-RADS technical recommendations 4

For Bile Duct Stones (Choledocholithiasis)

• CT abdomen without IV contrast can detect larger bile duct stones but has limited sensitivity 4
• MRCP (MR cholangiopancreatography) or ERCP are superior modalities for bile duct stone evaluation, not CT

Algorithm for Your Clinical Scenario

If the patient has flank pain or suspected kidney stones:

1. Order CT abdomen and pelvis without IV contrast (low-dose protocol) 1, 2
2. Specify thin-slice acquisition (1-1.5 mm) with coronal reformations 2
3. If patient has known chronic kidney disease with moderate-severe hydronephrosis on prior ultrasound, consider ultrasound first 2

If the patient has right upper quadrant pain or suspected bile duct/gallbladder stones:

1. Start with ultrasound of the right upper quadrant
2. If bile duct stones are suspected, order MRCP, not CT
3. If liver lesion characterization is needed, order CT abdomen with IV contrast multiphase 4

If both kidney stones AND liver lesions are suspected simultaneously:

1. Order CT abdomen and pelvis without and with IV contrast 1
2. The non-contrast phase detects kidney stones with 97% sensitivity 2
3. The contrast phases characterize liver lesions 4
4. This dual-phase approach provides both diagnostic capabilities in one study 1