Is Chronic Kidney Disease due to Cadmium Exposure Inevitable and Can it be Reversed?

Cadmium (Cd) is a metal with no nutritional or physiological value, but is found in most people because it is a contaminant in nearly all food types. The intestinal absorption rate determines the body burden of Cd because humans lack a physiologic mechanism for excretion of the metal. Most acquired Cd accumulates in the kidneys, in which the Cd content increases through age 50 but falls thereafter. The decline from maximal kidney content is probably due to release of Cd from injured tubular cells into urine and replacement of destroyed nephrons by scar tissue. Chronic kidney disease is diagnosed when the estimated glomerular filtration rate (eGFR) falls below 60 mL/min/1.73 m2, or when albuminuria is present. Albuminuria is defined as an albumin-to-creatinine ratio ≥ 30 mg/g creatinine in women or ≥ 20 mg/g creatinine in men that persists for at least 3 months. Generally, Cd-induced reductions in eGFR are not reversible, and Cd nephropathy may progress to end-stage kidney disease. There is no evidence that elimination of current environmental exposure can reverse Cd nephropathy, and no theoretical reason to believe that such a reversal is possible. This review provides an update of knowledge concerning CKD in population environmentally exposed to Cd. Special attention is devoted to mechanisms of Cd-induced albuminuria concurrently with eGFR reductions, and the difficult challenge of exposure guidelines sufficient to eliminate the risk of Cd-induced CKD is addressed.