(Photo contributor: Abhijeet Saha, MD)
*The authors acknowledge the special contributions of Anup Singh, MD, to prior edition.
Healthy children normally have protein in their urine, with a protein excretion rate of <4 mg/m2/h or <100 mg/m2/day throughout childhood. The upper limit of normal protein excretion is up to 150 mg/day. Albumin, relatively small in molecular size, tends to be the dominant constituent, and Tamm-Horsfall protein, a mucoprotein produced in the distal tubule, makes up the remainder.
Proteinuria in children can be transient, orthostatic, or pathologic. Transient proteinuria (often associated with fever or exercise) does not indicate underlying renal disease. Orthostatic proteinuria (elevated protein excretion when the subject is upright but normal protein excretion in recumbent position) occurs most commonly in school-aged children and rarely exceeds 1 g/m2/day. These patients do not have hematuria and have normal values of estimated glomerular filtration rate and C3 complement. Pathologic proteinuria is likely if proteinuria is associated with hematuria and/or the first morning urine protein-to-creatinine ratio is >0.2 in older children. Nephrotic-range proteinuria is defined as levels >40 mg/m2/h in 24 hours.
Nephrotic Syndrome (NS) Presenting with Edema and Proteinuria. (A, B) An 18-month-old child presented with periorbital and facial edema (A) and edema of the feet (B). Urinalysis showed 4+ proteinuria associated with hypoproteinemia. He was clinically diagnosed as minimal change NS. (Reproduced with permission from Shah BR, Laude TL, Atlas of Pediatric Clinical Diagnosis. WB Saunders; Philadelphia, PA, 2000.)
Nephrotic Syndrome (NS) Presenting with Edema and Proteinuria. (A) This adolescent male with NS presented with anasarca, hypoproteinemia, and heavy proteinuria. He had edema involving the scrotum, shaft, and foreskin of the penis. (B) Pitting edema is demonstrated here on the shin (edema of hypothyroidism or lymphedema is nonpitting). (Photo contributor: Mark Silverberg, MD.)
Severe Edema Associated with Heavy Proteinuria. (A, B) Severe edema of the lower extremity and edema of the vulva are seen in an adolescent girl who had hypoalbuminemia, heavy proteinuria, microscopic hematuria, and hypertension. Renal biopsy confirmed diagnosis of focal segmental glomerulosclerosis. (Photo contributor: Binita R. Shah, MD.)