What is the recommended diagnostic and treatment approach for a patient suspected of having kidney stones?

Diagnostic and Treatment Approach for Suspected Kidney Stones

Diagnostic Imaging

Low-dose non-contrast CT of the abdomen and pelvis is the gold standard initial imaging test for suspected kidney stones in most patients, with 97% sensitivity and 95% specificity. 1, 2

Primary Imaging Strategy

• Use low-dose non-contrast CT as first-line imaging for acute flank pain with suspected stone disease, as it provides precise stone measurement, exact ureteral location, and detection of secondary signs like hydronephrosis and perinephric stranding 1, 2
• Low-dose protocols maintain diagnostic accuracy (93.1% sensitivity, 96.6% specificity) while reducing radiation exposure compared to conventional CT 1
• Virtually all renal calculi are radiopaque on CT, allowing accurate detection even of small stones 2
• Stone size and location are critical for determining management—smaller, more proximal stones are more likely to pass spontaneously 1

Special Population Considerations

Pregnant patients:

• Use ultrasound as the primary imaging modality to avoid fetal radiation exposure 1, 2
• MRI without contrast (MRU) is the second-line option if ultrasound is inconclusive 1
• Low-dose CT should only be used as a last resort when other modalities fail to provide diagnostic information 1

Pediatric patients:

• Ultrasound is strongly recommended as first-line imaging, followed by KUB radiography or low-dose non-contrast CT if ultrasound is insufficient 1

Recurrent stone formers:

• Ultrasound combined with KUB radiography is reasonable for follow-up imaging to minimize cumulative radiation exposure 2
• This combination achieves 79-90% sensitivity 2

Imaging Pitfalls

• Plain KUB radiography alone has only 44-77% sensitivity and should not be used as the sole initial imaging modality 1
• Standard ultrasound has limited sensitivity (24-57% for stones, 45% for ureteral stones) but high specificity (88-94%) 1, 2
• Abdominal radiography has an appropriateness rating of only 3 (usually not appropriate) due to narrow visualization capabilities 1

Initial Clinical Evaluation

Immediate Assessment Requirements

Perform urgent evaluation in these high-risk scenarios:

• Patients with a solitary kidney 1
• Presence of fever suggesting infection 1
• Diagnostic uncertainty regarding renal colic 1

Laboratory Work-Up

Obtain these tests for all emergency stone patients:

• Urine dipstick analysis 1
• Serum creatinine, uric acid, ionized calcium 1
• Complete blood count and C-reactive protein (CRP) 1
• Sodium and potassium if intervention is planned 1

Stone analysis should be performed for all first-time stone formers to guide prevention strategies 1

Treatment Approach

Pain Management

NSAIDs (diclofenac, ibuprofen, metamizole) are first-line treatment for renal colic, as they reduce the need for additional analgesia compared to opioids 1

• Use the lowest effective NSAID dose due to cardiovascular and gastrointestinal risks 1
• Exercise caution with NSAIDs in patients with low glomerular filtration rate 1
• Opioids (hydromorphine, pentazocine, or tramadol—NOT pethidine) are second-line agents due to higher rates of vomiting and need for additional analgesia 1

Emergency Interventions

Urgent decompression via percutaneous nephrostomy or ureteral stenting is mandatory for:

• Sepsis in the setting of obstruction 1
• Anuria from bilateral obstruction or obstruction of a solitary kidney 1

Delay definitive stone treatment until sepsis resolves 1

Conservative vs. Invasive Management

Treatment decisions are based on:

• Stone size: <5 mm, 5-10 mm, 10-20 mm, >20 mm 1
• Stone location: upper/middle/lower calyx, renal pelvis, upper/middle/distal ureter 1
• Stone composition determined by CT density and structure 1

Larger and more proximally located stones have lower rates of spontaneous passage and require invasive therapy (percutaneous nephrolithotomy, ureteroscopy, or shock wave lithotripsy) 1

Metabolic Evaluation for Recurrence Prevention

Consider genetic testing with next-generation sequencing for:

• Children and adults ≤25 years old 1
• Adults >25 years with suspected inherited metabolic disorders 1
• Patients with recurrent stones (≥2 episodes), bilateral disease, or strong family history 1

Patients at high risk for recurrence require comprehensive 24-hour urine metabolic evaluation 1