The kidneys on the other hand is an organ common to all humans and thus it is not a sex organ at all.

This is true, but you know that kidneys are sexed, right? Male and female kidneys of many species have been found to differ not just in size and shape (in humans, female ones are smaller relative to body size and more elongated), but in the way they function too.

Also, although female kidneys are smaller, they have greater capacity than male kidneys as well as the ability to develop additional capacity when needed in order to handle the much greater blood volume that occurs in women's bodies during pregnancy. The difference in kidney capacity is one of the many reasons that males would not be able to sustain a pregnancy even if it were possible to implant uteruses into males. (In the gross experiment in which a uterus with an embryo inside was placed in a male rat, the male rat had to be connected to the female rat so he could rely on her kidney function.)

The differences in male and female kidney function helps explain the marked differences between the way kidney disease manifests in humans of the two sexes. Whilst male and female humans are equally likely to develop kidney disease, males progress to renal failure much more quickly. There are also marked difference in how the two sexes respond to treatments for kidney disease and related ailments. And there are great disparities in kidney transplants too. Women make up the majority - about 63% - of living donors of kidneys, but girls and women in need of kidney transplants are much less likely to be transplant recipients.

Most of the research on the difference in kidney function has been done on rats, but apparently rat kidneys are similar enough to human kidneys that legitimate parallels can be drawn.

[Researchers] found marked differences between sexes in the expression of genes associated with hormonal regulation, kidney disease and the kidney’s critical physiological activities. For example, they noticed differences between the sexes in the genes that code for enzymes that regulate blood pressure. The differences were especially evident in the proximal tubule region of the nephron, which is the workhorse tissue for reabsorption of essential factors such as glucose and metal ions, and the detoxification of drugs.

“These results highlight the need for a better understanding of sexual diversity within the human kidney,” McMahon said. “We know there are similarities between mice and humans in susceptibility to acute kidney injury — males are at a distinct disadvantage — and that sex differences can potentially impact drug studies and damage by kidney toxins.”

Indeed, the National Institutes of Health have emphasized that research needs to account for differences between sexes. Sex affects risk for disease, treatment and how people respond to medications. In the past, scientists studied male physiology and applied findings to women, so studies such as the new USC research underscore the importance of biological differences.

“Profound differences distinguish the male and female kidney,” McMahon said. “The kidney is the body’s regulator of fluid balance, and since women bear offspring, there are likely critical differences required in the mother for the benefit of both mother and offspring.”

The findings can benefit human health by improving an understanding of genetic programs that may influence drug trials, drug toxicity and cellular reprogramming, he said.

https://news.usc.edu/162474/kidney-gender-differences-usc-stem-cell-research/

https://www.biorxiv.org/content/10.1101/2021.02.03.429526v1.full