Paediatrics: Proteinuria

2021-03-04 12:00 AM

Proteinuria detected on dipstick testing should be confirmed using the EMU UP: Ucr ratio. If the proteinuria is combined with haematuria, investigations should be directed at the causes of haematuria and nephritis.

Proteinuria

This is defined as excessive urinary protein excretion. Protein may be found in the urine of healthy children and does not exceed 0.15g/24hr.

Detection of proteinuria

Urinalysis

Performed by dipstick testing (Table 11.1), this is a cheap, practicable, sensitive method that primarily detects albumin in the urine. It is less sensitive to other forms of proteinuria.

Urinalysis dipstick testing

Urinary protein: creatinine ratio (UP: UCr)

Collection of early morning urine (EMU) specimen for measurement of the urinary protein to creatinine ratio. Normal <20mg/mmol

24hr urinary protein excretion

This is the gold standard test and requires a 24hr collection of urine to estimate urinary protein excretion.

  • Normal: <30mg/24hr.
  • Microalbuminuria: 30–300mg/24hr.
  • Proteinuria: >300mg/24hr.

Causes

 Proteinuria may be due to benign or pathological causes.

Non-pathological proteinuria

  • Transient.
  • Fever.
  • Exercise.
  • Urinary tract infection (UTI).
  • Orthostatic proteinuria (postural proteinuria). This is a common cause of referral in older children. There is usually no history of significance and a normal examination. Investigations reveal a normal UP:UCr ratio in early morning urine with an elevated level in afternoon specimen (may require two 12hr collections). This is regarded as a benign finding and requires no treatment.

Pathological (persistent) proteinuria

This may be seen in a number of renal disorders including:

  • Nephrotic syndrome;
  • Glomerulonephritis;
  • Chronic kidney disease;
  • Tubular interstitial nephritis.

Investigations

Proteinuria detected on dipstick testing should be confirmed using the EMU UP: Ucr ratio. If the proteinuria is combined with haematuria, investigations should be directed at the causes of haematuria and nephritis.

  • A renal US scan should also be performed.
  • Patients with persistent proteinuria detected over a period of 6–12mths should be referred to a paediatric nephrology center for consideration for biopsy.