SFU Grading System Reference
| Grade | Pelvis | Calyces | Parenchyma | Clinical Significance |
|---|
| 0 |
Normal | Not visualized | Normal |
No hydronephrosis |
| I |
Mild splitting of renal pelvis | Not dilated | Normal |
Clinically insignificant; may be physiologic |
| II |
Moderate pelvis dilation ± calyces visible | Few seen | Normal |
Significant — warrants further evaluation |
| III |
Large dilation | All calyces dilated, rounded | Normal thickness |
Significant obstruction — urology consultation |
| IV |
Severe dilation | All calyces severely dilated | Thinned/atrophic |
Severe/longstanding — urgent urology |
Anteroposterior Diameter (APD) Reference
| APD (mm) | Interpretation | Recommended Action |
|---|
| < 5 | Normal | No further workup if no symptoms |
| 5–9 | Mild | Clinical correlation; consider follow-up ultrasound |
| 10–14 | Moderate | CT urography or repeat US in 4–6 weeks; urology if persists |
| 15–19 | Moderate-Severe | CT urography; urology consultation |
| ≥ 20 | Severe | Urgent urology consultation; consider decompression |
APD measured in the transverse plane at the renal pelvis. Adult thresholds; pediatric values differ.
Interactive Grading — Select Grade
Schematic representation — Curvilinear probe, longitudinal axis
Clinical Integration — Renal Colic Workup
Quick Reference — Ocular Nerve Sheath Diameter
Normal ONSD: < 5.0 mm (measured 3 mm behind the globe)
Elevated ICP threshold: ≥ 5.0 mm correlates with ICP > 20 mmHg (sensitivity ~84%, specificity ~82%)
Probe: Linear 7.5–12 MHz · Closed eyelid · Transverse and longitudinal · Average bilateral measurements
Dubourg J, et al. Intensive Care Med 2011. PMID 21305258
Evidence Base
- Fernbach SK, et al. Ultrasound grading of hydronephrosis (SFU system). Pediatr Radiol 1993. PMID 8433268
- Smith-Bindman R, et al. Ultrasonography vs CT for suspected nephrolithiasis (STONE trial). NEJM 2014. PMID 24988557
- Nicolau C, et al. Normal values for renal length in adults. Eur Radiol 2003. PMID 12652393
- Watkins S, et al. POCUS for hydronephrosis and ureteral stones. Emerg Med Clin North Am 2019.
- Gaspari RJ, et al. Emergency ultrasound for hydronephrosis. Acad Emerg Med 2009. PMID 19187399
YBEMUS · Guy Youngblood, MD, FACEP, FAAEM
CCEMRP · BCM/CHRISTUS Children's PEM Fellowship
For educational use. Not a substitute for clinical judgment.