Normal Kidney Parenchymal Thickness in Adults
The normal renal parenchymal thickness in adults ranges from approximately 1.5 to 2.0 cm, with the left kidney typically measuring slightly thicker than the right kidney. 1
Specific Normative Values
Average parenchymal thickness measurements:
- Right kidney: 1.85 ± 0.20 cm 1
- Left kidney: 1.95 ± 0.19 cm 1
- The left kidney demonstrates statistically higher parenchymal thickness compared to the right kidney 1
Age-Related Changes
Parenchymal thickness decreases with advancing age, showing a significant negative correlation with age, primarily due to cortical reduction rather than medullary changes 1, 2. This age-related decline occurs almost entirely because of parenchymal reduction, while the medullary thickness remains relatively stable until advanced chronic kidney disease develops 2, 3.
Body Habitus Correlations
Parenchymal thickness exhibits strong positive correlations with:
No significant difference exists in mean parenchymal thickness between genders 1.
Clinical Significance for Chronic Kidney Disease
Parenchymal thickness ≤1.5 cm suggests chronic renal disease, though this measurement alone should not preclude further evaluation 4. In patients with confirmed chronic kidney disease, 64% demonstrated parenchymal thickness ≤1.5 cm, compared to only 7-38% in other renal conditions 4.
Important caveats:
- Both kidney size and parenchymal thickness decrease in chronic kidney disease, but normal-sized kidneys with preserved parenchymal thickness do not exclude CKD, particularly in diabetic nephropathy, infiltrative disorders, and early-stage disease 5, 6
- Some patients with parenchymal thickness ≤1.5 cm still retain potential for functional improvement, so this measurement should not be used as the sole criterion to avoid renal biopsy 4
- Left cortical thickness is particularly useful for detecting early changes in renal function and may be the strongest predictor in early-stage disease 2
Measurement Technique
Parenchymal thickness should be measured from the outer renal cortical margin to the outer margin of the sinus echoes at the three major poles (upper pole, mid-kidney, and lower pole) 1. The American College of Radiology guidelines note that renal length >10 cm in the third decade is considered normal, with both kidney size and parenchymal thickness serving as secondary markers to differentiate acute kidney injury from chronic kidney disease 5.