Narmac, 

Interesting idea about kidney functioning to remove amyloid. There very well could be a connection between kidney disease and cognitive decline. Today's ASN Resverlogix poster reported that elevated alkaline phosphatase is associated with poorer cognitive function and increased prevalence of CKD. Furthermore, the background of the poster states:

"Increased circulating levels of ALP associate with cognitive impairment, Alzheimer’s disease and vascular dementia. Possible pathogenic mechanisms linking ALP to impaired cognition include disturbance of the blood brain barrier, impaired microcirculation, and dephosphorylation of tau."

Association of Serum Alkaline Phosphatase with CKD and Cognitive Function in Patients with Diabetes and Acute Coronary Syndrome