What are the common causes of chronic kidney disease at 26?

It is not feasible to address the issue without context. Acute kidney disease may be due to drug toxicity, injury to muscles, post-infectious kidney inflammation, kidney stones, polycystic kidney disease, and more. Visit this site for information on chronic kidney disease: https://www.mayoclinic.org/diseases-conditions/chronic-kidney-disease/symptoms-causes/syc-20354521

This will depend on you ethnic background and where you live or have lived and worked. In general I would think in the following order: diabetes, untreated high blood pressure (especially if of African descent), polycystic kidney disease if it runs in your family, pregnancy/eclampsia, chemical injury by meds/work environment (a sugar cane worker in Central American). So need much more info.