Evaluation of Proteinuria Craig Dobson, MD CPT, MC, USAR NCC Pediatrics

What is proteinuria, baby? Some degree is always present. Tamm-Horstfeld Proteins are actually secreted by tubules themselves. Urine dipstick is extremely sensitive Normal 24hr Protein output < 200mg/dL for adults. < 20mg/kg/day for children Spot protein detection must always be interpreted in the context of concentration of urine. 1+ Protein (10mg/dL) @ SG 1.030 is not concerning. 1+ Protein @ SG 1.010 may be important. Other renal signs, especially edema, should lead you to believe the result more.

False Postives for UA Protein pH > 8 Hematuria Leukouria (incl. UTI) Fever Not really a false positive. Causes leaky basement membrane. Chlorhexidine wash to clean perineum. Vaginal/seminal secretions Menstrual blood Exercise Concentration

How do we achieve a better estimation of quantity of proteinuria? Spot Urine Protein/Creatinine Ratio Normal <0.3 for children over age two. Normal <0.5 under age two. Well validated/nearly equivalent to 24hr Urine. 24hr Urine Collection Very difficult in children. Usually performed incorrectly. Many peds nephrologists only use Prot/Cr.

Causes of Proteinuria Orthostatic Proteinuria Pathogenesis Extremely common. Incidence 7-12% of adults. Pathogenesis Now proven to be laxity of support to kidney allows kidney to fall slightly when standing. Kinking of renal vein occurs. Back pressure causes minor spillage of protein. Absolutely a benign condition! No renal impairment/failure associated with it.

Other causes of Proteinuria Glomerular Glomerulonephritis Refers to any inflammation of glomerulus. Should have glomerular hematuria (RBC casts, abnormal shaped RBCs in urine) Minimal change disease IgA nephropathy Also should have RBCs. Tubular Acute Tubular Necrosis Fanconi’s Sx. Lowe’s Syndrome Cystinuria High Plasma Proteins Myoglobinuria/Hemoglobinuria Leukemia Urinary Tract Tumor Inflammation

Evaluation of Isolated Proteinuria First r/o orthostatic proteinuria First morning void after lying recumbant for at least 6hrs. (Also rules out exercise as a factor.) Urine Protein/Creatinine ratio If >0.2, proceed to further work-up Referral to Nephro if >0.2 Labs BUN, Cr, C3, ASO, ANA Consider Hep B/C, HIV Imaging Consider renal U/S.

Nephrotic syndrome Refers to the degree of proteinuria, not a disease by itself. Prot/Cr ratio 0.5-2.5 is significant proteinuria. >=2.5 is nephrotic range. Equivalent to 2.5g/day in adult. May be caused by any of the causes of proteinuria including nephritis. Most common cause is minimal change disease. Treatment is trial of steroids Renal biopsy for failure to respond to steroids.