Tests would have likely given you the information to know if it was kidney disease for sure. Diseased kidneys can block the intestinal tract and cause constipation/impaction…but impaction can come from what the chameleon was eating as well.
This might help…
”Not wanting to eat, lethargy, and sunken eyes are early signs. A foul or unusual odor may be noticed at more advanced stages. A white sheen may be seen in the mouth”…
”Commonly, reptiles with advanced kidney disease will vomit or regurgitate if
force fed”…
“Other signs that your reptile may have kidney disease that your veterinarian might notice include weakness; lying on the table rather than sitting in an alert and erect posture; bad breath (not yours, your reptile’s!); and dehydration causing sunken eyes and thick ropy mucus in the mouth”…
https://veterinarypartner.vin.com/default.aspx?pid=19239&catId=102919&id=8148630