Propositiones de lithiasi tōn nephrōn

It is cured with more difficulty when the affected bodies are thin, Galen in the same place, chapter 11.

XXIIX.
It is generated more easily in fatter people, because the material from which the stone is wont to be generated can be retained more [easily]: in thin people, it is for the most part propelled into the bladder.

XXIX.
Boys are more susceptible to stones of the bladder: old men and those who are more adult, to those of the kidneys. Because in boys, since the heat is strong, the expulsive force is robust, and the substance of the kidneys is soft and loose, it is propelled more easily to the bladder: in old men, the expulsive force is weak, and the flesh of the kidneys is drier and more compact, from which it happens that they are retained longer and are hardened more, as Hippocrates in book 6 of On Popular Diseases, commentary 3, text 15, and Aetius in the cited places teach.

XXX.
In the same way, women suffer more rarely from kidney stones on account of their menstrual purges and the laxity of the passages.

XXXI.
Those with arthritis easily become nephritic, because they abound in thick and earthy substances collected through constant poor digestion. The long lying on the back and kidneys aids the growth of stones in these people.

XXXII.
The sand that is cast out shows that the stone is still friable and sandy, and then there is some hope that it can be broken and cured: if, however, nothing of the sort is cast out, it signifies that it is quite hard (as is usual in an inveterate disease), and thus there is not great hope of health.

XXXIII.
Stones that are round or smooth are excreted more easily than rough and angular ones, and the patients are less tortured by them.