Pediatric Urologic Imaging and Diagnostic Testing
Core concepts
Know the indications and limitations of pediatric urologic imaging: ultrasound, voiding cystourethrogram, renal scintigraphy (DMSA, MAG3), CT, and MRI. Understand radiation exposure concerns and the ALARA principle. Recognize the role of DMSA for cortical scarring and MAG3 for obstruction and function. Know when VCUG is indicated: recurrent febrile UTI, suspected reflux, and posterior urethral valves. Understand the role of urodynamics in neurogenic bladder and the interpretation of uroflow and post-void residual. Recognize the value of contrast studies in trauma and the limitations of ultrasound in detecting reflux.
Traps
- Using ultrasound to diagnose reflux; it cannot.
- Ordering CT when ultrasound or MRI would suffice.
- Misinterpreting MAG3 without accounting for hydration and bladder catheterization.
- Forgetting that VCUG is the study of choice for urethral anatomy in males.
Worked example
A child with recurrent febrile UTI and a normal ultrasound may still need a VCUG to evaluate for reflux; DMSA can assess cortical scarring.
Rule of thumb
Ultrasound screens, VCUG diagnoses reflux and urethral anatomy, and scintigraphy quantifies function and scarring.