Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (538 page)

   Idiopathic: the most common cause of hypercalciuria and defined as an excess urinary calcium excretion without an apparent underlying etiology. As a result, diagnosis requires exclusion of all other causes of hypercalciuria. This condition is familial in nature and present in 2–6% of asymptomatic children.

   Patients with absorptive hypercalciuria will have lowered urine calcium with dietary restriction and therefore can be differentiated from patients with renal or resorptive hypercalciuria.

   Laboratory Findings

   Increased urinary calcium excretion (see definition above) and urinary calcium/creatinine ratio.

   Blood calcium level is typically normal. Other laboratory tests such as serum creatinine, phosphorus, parathyroid hormone (PTH), and vitamin D levels help identify the cause of hypercalciuria.

HYPERTENSIVE NEPHROSCLEROSIS

   Definition

   This condition is characterized by thickening and luminal narrowing of the large and small arteries and arterioles of the kidney and sclerosis of the glomeruli secondary to hypertension.

   It is classified as benign or malignant (rare) depending the severity of hypertension and rapidity of the arteriolar change. With the malignant form, severe high blood pressure can lead to acute kidney injury and hematuria.

   Who Should Be Suspected?

   Patients with long history of hypertension presenting with slowly progressive elevations in serum BUN and creatinine levels and mild proteinuria.

   Blacks, patients with marked elevations of blood pressure, and patients with diabetic nephropathy are at higher risk.

   Laboratory Findings

   Benign nephrosclerosis: elevated BUN and creatinine, mild proteinuria (usually <1 g/day), and normal or near-normal urine sediment.