Size is only one of the many important differences that have been found in male & female kidneys. Sex

of donor and recipient plays a larger role in kidney transplants than previously assumed. Female donor kidneys do not function as well in men -- due to their smaller size. Women have a higher risk of rejecting a male donor kidney.

https://journals.physiology.org/doi/full/10.1152/ajprenal.00584.2018

Major differences have been found in other human organs too, including the heart.

Large studies have been carried out with respect to the cardiac functions among the different sexes in both animals and humans, though the studies on male predominate. There is increasing evidence that the biological sex play a significant role in cardiac functioning, as well as in the occurrence and outcome of cardiac disease. Female sex tends to have an upper hand in the heart function which is progressively lost once they attain menopause. Sex differences have been reported in left ventricular hypertrophy, cardiac remodelling with aging, arrhythmogenic activity and post-infarct myocardial salvage.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190707/

The anatomic location of the major vessels in the heart, lung, and most organs are indistinguishable among the sexes. Similarly, the cardiovascular systems of males and females have the same formed elements circulating in the blood, the vessels are composed of the same cell types, and the union of the elements perform the same functions. Healthy men and women are in homeostasis. Consequently, it makes sense to conclude that the functions and functional responses of all of these common elements are the same in men and women, right? Well, no, not necessarily, and that is where the tale becomes interesting. The take-home message of this monograph will be that while men and women are indeed in homeostasis and they possess the same structural elements, how those components function to achieve homeostasis with respect to the cardiovascular system differs (from subtly to profoundly). The manifestation of these differences has a real outcome: how and when cardiovascular disease occurs, how disease can be prevented, and what can be done to ameliorate or treat its manifestations effectively https://journals.physiology.org/doi/full/10.1152/advan.00099.2006

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6298433/

https://www.cardofmich.com/men-women-heart-differences/

There are many marked differences - starting at birth - between the lung tissue, lung secretions and lung function of males and females that go way, way beyond size differences too. Male and female humans actually breathe differently! I first twigged to some of these differences decades ago because I grew up with a brother & sister who both had cystic fibrosis, which ravages the lungs - and even in the 1950s & early 1960s when CF was first being understood & described in medical literature, notable differences were observed in how the same disease from the same exact genetic flaw (Delta F-508) manifested in the two sexes even from the same parentage & household and with the same medical treatment, nutrition, level of exercise, home care, physical therapy, interventions, etc. Generally speaking girls with CF tend to get much sicker much sooner than boys, and they die younger.