Diagnostic Evaluation of Proteinuria
Microscopic Urinalysis
When proteinuria is found on a dipstick urinalysis, the urinary sediment should be examined microscopically. The findings of the microscopic examination and associated disorders are summarized in Table 5. Dysmorphic erythrocytes are a result of cell insult secondary to osmotic shift in the nephron, indicating glomerular disease. Gross hematuria will cause proteinuria on dipstick urinalysis, but microscopic hematuria will not.
Findings suggestive of infection on microscopic urinalysis mandate antibiotic treatment and then repeated dipstick testing. Nephrology consultation may be warranted if sediment findings indicate underlying renal disease.
Transient Proteinuria
If the results of microscopic urinalysis are inconclusive and the dipstick urinalysis shows trace to 2+ protein, the dipstick test should be repeated on a morning specimen at least twice during the next month (when proteinuria [3+ or 4+] is
If a subsequent dipstick test result is negative, the patient has transient proteinuria. This condition is not associated with increased morbidity and mortality, and specific follow-up is not indicated.
| Interpretation of Findings on Microscopic Examination of Urine | |
| Microscopic finding | Pathologic process |
| Fatty casts,free fat or oval fat bodies | Nephrotic range proteinuria (>3.5 g per 24 hours) |
| Leukocytes, leukocyte casts with bacteria | Urinary tract infection |
| Leukocytes,leukocyte casts without bacteria | Renal interstitial disease |
| Normal-shaped erythrocytes | Suggestive of lower urinary tract lesion |
| Dysmorphic erythrocytes | Suggestive of upper urinary tract lesion |
| Erythrocyte casts | Glomerular disease |
| Waxy,granular or cellular casts | Advanced chronic renal disease |
| Eosinophiluria * | Suggestive of drug-induced acute interstitial nephritis |
| Hyaline casts |
No renal disease;present with dehydration and with diuretic therapy |
| *—A Wright stain of the urine specimen is necessary to detect eosinophiluria | |
