Differential diagnosis of Proteinuria

Question 1

What is the gold standard for protein analysis in the urine ?

Answer 1

• 24-hour urine collection to quantify ​amount of protein ​in urine

Question 2

Microalbuminuria: differential diagnosis

Answer 2

30-300 mg/L of urine or 30-300 mg/24h

• early diabetes
• essential HTN
• early stages of glomerulonephritis, especially If RBCs or RBC casts (glomerulonephritis also causes microscopic hematuria)

Question 3

Macroalbuminuria: differential diagnosis

Answer 3

300-3500 mg/L of urine or 300-3500mg/24h
+ RBCs or RBC cast on urinalysis

• same as from the differential diagnosis in microalbuminuria
• myeloma associated kidney disease (myeloma -> a type of blood cancer)
• intermittent proteinuria (can be caused by high fever, and heavy exercise)
• congestive HF
• fever
• exercise

Question 4

Proteinuria at a nephrotic range:

Answer 4

> 3500 mg/d or >3500 mg/24h
+ RBCs or RBC cast on urinalysis
- diabetes
- amyloidosis
- minimal change disease (nephrotic syndrome)
- FSGS (focal segmental glomerulosclerosis, nephrotic syndrome)
- membranous glomerulopathy (nephrotic syndrome)
- IgA nephropathy (nephritic syndrome)

Question 5

What to do to determine if the proteinuria is transient or not ?

Answer 5

• urinalysis and microscopic examination on at least 3 seperate occasions

Question 6

What to do to determine if the proteinuria origins ?

Answer 6

• urinalysis -> look for dysmorphic RBCs or casts
• look creatinine, albumin, cholesterol serum level -> tells about the renal function.
  Increased cholesterol level (hyperlipidemia) can indicate nephrotic syndrome.
• if autoAbs in the blood -> could be autoimmune disorder, or post-strep glomerulonephritis
• measure HbA1c -> determine if patient is diabetic
• Renal US -> look for size and echogenicity of kidneys

Question 7

When would you perform a renal biopsy ?

Answer 7

• if the proteinuria is persistent and unresponsive to nonspecific treatment
• if proteinuria increases or if renal function declines.

Question 8

When to perform a nonspecific treatment ?

Answer 8

• when suspicion of disease, but no renal confirmation

- most common cause of proteinuria in children: minimal change disease

Question 9

Drugs that could be used in nonspecific treatment:

Answer 9

• ACEi/ARBs
• Normalizing BP in HT
• Diuretics