Are the kidneys the same size?
No. The left kidney is (probably) slightly bigger than the right one. One study showed the left side had an average renal length of around 11.2 cm, whereas the right-side measured 10.9 cm (Emamian, 1993).
Another study did not confirm a difference in length but did show the kidney width and thickness were different (Chaudary, 2023):
- Right kidney – length 10.7 cm, width 4.5 cm, with a parenchymal (outer) thickness of 0.91 cm
- Left kidney – length 10.7 cm, width 4.8 cm, with a parenchymal thickness of 0.76 cm. So the right kidney was less wide but thicker.
The kidneys are near the middle of your lower back, on either side of the spine, just below the rib cage.
Anyway. They are bean-shaped organs and about the size of your palm, and and weigh 150-200g.
Location of kidneys
Your kidneys are lopsided (asymmetrical)
As described above, your right kidney tends to be smaller and sit a little lower than your left one because it is pushed down by the liver – as shown in the diagram above.
Note. When one kidney has reduced function or is absent, the other may undergo compensatory enlargement (becomes larger). How that happens is unclear.
Other aspects of renal size
The Emamian, 1993 study also showed that renal size decreased with age, almost entirely because of parenchymal reduction. Renal volume correlated best with total body area. Renal length correlated best with body height.
Whereas the Chaudary, 2023 study only showed weak positive correlations between kidney parameters and body height, body weight, BSA, and BMI. It was a smaller study so that may be a factor in these observations.
Other resources
Anatomy, structure and size of the kidney
Do obese children have larger kidneys?
10 kidney facts
Where are the kidneys located?
What do the kidneys do (7 functions)?
Last Reviewed on 22 May 2024