A number of theological dictionaries define כליה as simply kidneys rather than simply a generic for any inner part. The crux of the argument for kidneys seems to be that כליה is always used in its plural form כליות and kidneys come in pairs. However, a glaring failure to this argument seems, to me, to be the lack of the dual number construction. So far, I have been unable to find any articles that deal with the linguistic evidence for understanding כליה as kidneys in ancient Hebrew culture or anything that addresses the unusual lack of a dual number for something that comes in pairs. Anyone know of any resources that might cover this in greater detail?