What is the workup for a patient presenting with flank pain, urinary retention, colicky intermittent pain, hematuria, and pyuria?

Diagnostic Workup for Flank Pain with Urinary Retention, Colicky Pain, Hematuria, and Pyuria

Non-contrast CT scan of the abdomen and pelvis is the first-line imaging study for patients presenting with flank pain, hematuria, and pyuria, as it has the highest sensitivity (98-100%) for detecting urolithiasis and can identify alternative diagnoses. 1, 2

Initial Assessment

Laboratory Tests:

• Urinalysis to confirm hematuria and pyuria
• Urine culture to identify causative organism
• Complete blood count to assess for leukocytosis
• Basic metabolic panel to evaluate renal function
• Blood cultures if fever or signs of systemic infection are present

Imaging Studies:

1. First-line: Non-contrast CT abdomen and pelvis

   • Gold standard for detecting urinary stones with sensitivity of 96-100% and specificity of 98-100% 1
   • Can identify stone size, location, and degree of obstruction
   • Helps detect complications such as hydronephrosis
   • Can identify alternative diagnoses

2. Alternative if CT contraindicated:

   • Ultrasound of kidneys, ureters, and bladder
     • Less sensitive than CT (sensitivity 24-57% for stone detection) 1
     • Highly sensitive (up to 100%) for detecting hydronephrosis 1
     • Addition of color Doppler with twinkling artifact increases sensitivity for small stones 1

Additional Diagnostic Considerations

For patients with confirmed urolithiasis:

• Assess stone size and location to determine likelihood of spontaneous passage
  • Stones >5mm are less likely to pass spontaneously 1
  • Proximal ureteral stones have lower rates of spontaneous passage 1

For patients with urinary retention:

• Post-void residual measurement
• Consider urodynamic testing if neurogenic bladder is suspected 1
• Cystoscopy if urethral stricture, bladder stones, or bladder cancer is suspected 1

For patients with recurrent symptoms:

• Consider metabolic evaluation for stone formers
• Low-dose CT or ultrasound for follow-up imaging 1

Special Considerations

If infection is suspected:

• Urgent drainage may be required if obstructive pyelonephritis is present
• Monitor for signs of sepsis or autonomic dysreflexia (in patients with spinal cord injury) 1

If hematuria persists after stone passage:

• Complete hematuria workup may be necessary to rule out malignancy
• Cystoscopy should be considered, especially in patients >35 years 2

Potential Alternative Diagnoses

When evaluating patients with these symptoms, consider these alternative diagnoses:

• Pyelonephritis
• Renal infarction
• Medullary sponge kidney 3
• Page kidney (subcapsular hematoma causing hypertension) 4
• Loin pain hematuria syndrome 5, 6

Pitfalls to Avoid

1. Relying solely on hematuria: While hematuria is present in approximately 93% of patients with urolithiasis, 5-7% of patients with confirmed stones may not have hematuria 7

2. Missing signs of infection: Pyuria with flank pain may indicate pyelonephritis, which requires prompt antibiotic therapy

3. Overlooking neurogenic causes: In patients with history of neurological disorders, consider neurogenic lower urinary tract dysfunction 1

4. Inadequate follow-up: Patients with moderate to severe hydronephrosis often require intervention and close monitoring 2

5. Contrast-enhanced CT limitations: While non-contrast CT is preferred for initial evaluation, contrast-enhanced CT may obscure small stones within the renal collecting system 1

By following this systematic approach, clinicians can effectively diagnose and manage patients presenting with this constellation of symptoms while minimizing complications and identifying alternative diagnoses when appropriate.