Chronic kidney disease

What it is

Chronic kidney disease is an abnormality of kidney structure or function that is present for 3 or more months. The tubules atrophy and the interstitial tissue undergoes fibrosis. On imaging the kidneys are small. Chronic kidney disease is the most common cause of small kidneys and is the final common pathway of many chronic conditions; the other named cause of small kidneys is chronic glomerulonephritis, which leads to scarring and atrophy.

How it presents

What is felt first is often the anemia: fatiguability and decreased exercise tolerance. Nausea and vomiting are the clinical signs that matter in uremia. Salt and water retention shows as systemic volume overload, with hypertension and pitting edema.

How it is diagnosed

The diagnosis rests on a persistent impaired creatinine clearance, not on one reading. To take a described example, an eGFR of 39 mL/min/1.73 m2 that stays low over 8 months in an older patient with longstanding hypertension and dyslipidemia is what is meant by persistent.

The biochemical profile of untreated disease is a low calcium with a high phosphate, a high PTH and a high ALP. The route to it: the fall in glomerular filtration reduces renal excretion of phosphate, the phosphate that remains binds ionized calcium, calcium in the blood falls, the inhibition of PTH release falls with it, and PTH in the blood rises.