SFU Grading System: 0–4 ultrasound grading scale for hydronephrosis based on pelvic/calyceal dilation and parenchymal thickness; grades 3–4 have higher surgical intervention rates.
The Society for Fetal Urology (SFU) grading system is the standard ultrasound classification for hydronephrosis, graded 0–4 based on renal pelvis dilation, calyceal involvement, and parenchymal thickness. Grade 0 = normal; Grade 1 = mild pelvic dilation; Grade 2 = moderate pelvic and calyceal dilation; Grade 3 = diffuse caliectasis; Grade 4 = Grade 3 plus parenchymal thinning. Grades 3–4 carry higher surgical intervention rates.