Increased serum alkaline phosphatase activity: a possible indicator of renal damage.

Increased levels of serum alkaline phosphatase (ALP) (E.C.3.1.3.1.) were observed in 25 patients with various urological conditions involving the kidneys: malignancy, complicated nephrolithiasis, and surgical and percutaneous manipulations. Other possible sources for increased ALP level, mainly hepatic and osseous, were excluded by history, laboratory tests, and liver and bone imaging. Studies of isoenzymes of ALP did not show a distinctive pattern. ALP levels returned to the normal range by treating the underlying lesions involving the kidney: nephrectomy, complete removal of stones, or removal of nephrostomy. The increase in serum ALP activity may be derived from the injury to the brush border membrane of the renal tubular cells. Renal function impairment and contrast media induced nephrotoxicity may also be responsible for the increased serum ALP. Serum ALP may be a marker for involvement of the kidneys in pathological processes and an indicator of complete treatment. This clinical observation is worthy of further study.