152 A.R. Watson
family history of deafness or progressive nephritis then Alport’s syndrome is a likely diagnosis. This can lead to progressive nephritis needing dialysis and transplantation, especially in boys as 80–90% of cases are X-linked dominant.
14.2 Proteinuria
Protein may be found in the urine of healthy children and usually does not exceed 0.15 g/24 h. It is usually detected on dipstick testing which predominantly detects albumin in the urine (Table 14.1).3
14.2.1 Quantification of Proteinuria
We have largely abandoned 24 h urine collection in children but instead collect an early morning urine (EMU) for measurement of the urinary protein : creatinine ratio. (normal <20 mg protein/mmol creatinine)
Microalbuminuria will not be detected by dipsticks but is often assessed in patients with diabetes and is defined as UA:UCr of >2.5 mg/mmol.
14.2.2 Causes of Proteinuria
Proteinuria may be due to benign or pathological causes.
TABLE 14.1. Urinalysis by dipstick testing.
Test result |
Equivalent protein estimate |
|
(g/L) |
+ |
0.2 |
++ |
1.0 |
+++ |
3.0 |
++++³20
Chapter 14. Hematuria and Proteinuria 153
14.2.2.1 Non-Pathological Proteinuria
•Transient
•Fever
•Exercise
•Urinary tract infection
14.2.2.2 Orthostatic Proteinuria (Postural Proteinuria)
This is a common cause of referral in older children. There is usually no history of significance and examination is normal. The UP/UCr ratio in the early morning urine should be normal with an elevated level in the afternoon specimen. If confirmed and no other findings on history and examination then the proteinuria should be regarded as a benign finding and requires no investigation or treatment.
14.2.2.3 Pathological Proteinuria
•Nephrotic syndrome is recognized as heavy proteinuria (>200 mg/mmol), hypoalbuminemia (<25 g/L) and edema
•Glomerulonephritis is recognized by associated hematuria, clinical features and investigation
•Chronic kidney disease is associated with glomerulosclerosis or a reduced nephron mass from any cause resulting in hyperfiltration
Current consensus is to treat proteinuria associated with suspected low nephron mass with ACE inhibitors which may slow the rate of CKD progression. Hence documentation of persistent proteinuria and referral to pediatric nephrology is important.
•Tubular disease may give rise to proteinuria and require measurement of urine NAG and urine retinal binding protein to creatinine ratios.