Renal dysfunction detected by beta-2 microglobulinuria in sick neonates.

OBJECTIVE: To assess renal involvement in sick neonates referred to Neonatal Intensive Care Unit (NICU) using standard renal parameters and urinary beta 2 microglobulin (B2M) excretion. DESIGN: Descriptive study. SETTING: Level II NICU and Nephrology Division of Pediatric Tertiary hospital. SUBJECTS: Forty six term sick neonates transferred for neonatal care and forty healthy term neonates who served as normal controls for urinary B2M excretion. METHODS: Standard tests including estimation of BUN, serum creatinine, blood pH, serum bicarbonate, serum and urinary electrolytes, urine output, and urinalysis. Urinary B2M levels were estimated from urine collected on day 1 (D1) and day 3 (D3) in all and 18 neonates were tested on day 7 (D7) by radio-immunoassay method. RESULTS: Statistically significant elevation of mean values of urinary B2M were noted when sick neonates were compared with normal controls irrespective of primary disease, indicating tubular dysfunction (41/46 = 90%), whilst only 7 of these (17%) had abnormalities indicating renal involvement when judged by standard tests. Very high levels of urinary B2M were noted with birth asphyxia (n = 9), sepsis (n = 8) and renal disease (n = 7). Transient elevation of urinary B2M was noted in meconium aspiration syndrome (n = 4). Ten surgical cases with non renal congenital malformations showed high urinary B2M and 12/18 tested on D7 had persistently high urinary B2M due to multiple factors. CONCLUSIONS: Elevated urinary B2M in 90% sick neonates with apparently normal renal parameters in majority (34/41) indicates subclinical proximal tubular dysfunction especially in neonates with asphyxia, sepsis and congenital malformations. Persistent elevation of urinary B2M appear to be a sensitive diagnostic indicator for defining a group of neonates with subtle renal tubular dysfunction, the clinical relevance of which on long term basis is a subject for future study.

Urinary red cell morphology to detect site of hematuria.

We studied the urinary RBC morphology in 87 consecutive cases of significant hematuria by 3 commonly used methods: (a) light microscopy of the unstained urinary sediment; (b) phase contrast microscopy of the unstained urinary sediment; and (c) Wright's staining of the urinary sediment, in order to compare the sensitivity of these methods in detecting dysmorphic RBCs and thus predicting the site of hematuria. The clinical data and the relevant investigations were made available after the morphology of RBCs in the urine was identified. Out of the 87 patients, 45 had a glomerular and 42 had a nonglomerular cause o hematuria. Phase contrast microscopy showed a sensitivity of 91.1%, Wright's stain of 82.2% and light microscopy of 66.7% in detecting a glomerular source of hematuria. Nonglomerular hematuria could be detected in 92.9% cases by each of the 3 methods. It is concluded that phase contrast microscopy is most sensitive for the detection of dysmorphic RBCs in the urine, Wright's stain nearly as sensitive whilst light microscopy of the unstained sediment is least sensitive. Urinary RBC morphology is a useful adjunct in the diagnosis of hematuria and saves the patients from unnecessary investigations.