Yes, because we need calcium and oxalic acid for kidney stone formation. Since spinach is rich in oxalic acid, the risk for kidney stone formation is there.

If you consume more calcium then the risk increases. More than 90% of the kidney stones are calcium oxalate stones.

I am not telling you to avoid spinach. The easy way to avoid this risk is, drink a lot of fluids. Three to four litres a day and 70 to 80% of this must be water, aerated or pure drinking water and then you need not worry about the kidney stones. If you are sweating more, then you have to drink more.

There are several other vegetables which have more oxalic acid than spinach. If you are prone to kidney stone formation, eat less spinach and other vegetables containing oxalates.