Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (542 page)

   FENa >1% indicates tubular damage.

   Hyperchloremic metabolic acidosis suggests tubulointerstitial injury.

   Kidney biopsy confirms the diagnosis.

MINIMAL CHANGE DISEASE

   Definition

This condition is the most common cause of nephrotic syndrome in the pediatric population, accounting for 70–90% of cases in children <10 years and 50% of cases in older children. It is also an important cause of nephrotic syndrome in adults (10–15% of cases).

   Who Should Be Suspected?

Candidates are patients with sudden onset of nephrotic syndrome, which may be a primary occurrence or secondary to drugs, infections, autoimmune disorders, or malignancies, particularly hematologic malignancies (Hodgkin disease, non-Hodgkin lymphoma, or leukemia).

   Laboratory Findings

   Marked proteinuria (>3.5 g/day), mostly albuminuria.

   Hypoalbuminemia (<2 g/dL) and, in most cases, hyperlipidemia.

   Normal findings by light microscopy and absence of immunoglobulin or complement deposits by immunofluorescence microscopy.

   Diffuse effacement of the podocyte foot processes is visible on EM. Microscopic hematuria occurs in less than one third of patients.

NEPHRITIC SYNDROME

   Definition

   Acute nephritic syndrome is an immune disorder characterized by glomerulonephritis and acute onset of hematuria, proteinuria, and declining renal function.

   Two patterns can be distinguished: