Il Laboratorio nella valutazione della funzione renale in gravidanza
Laboratory medicine for the assessment of kidney function during pregnancy

AUTORI

ABSTRACT

Laboratory medicine for the assessment of kidney function during pregnancy

The early identification of kidney function impairment during pregnancy is crucial to prevent the onset of severe maternal diseases, such as hypertension, diabetic nephropathy, preeclampsia, urinary tract infections, and neonatal adverse outcomes, such as prematurity and intrauterine growth restriction. In pregnant women who developed chronic kidney disease before gestation, the weekly monitoring of serum/plasma creatinine and albuminuria allows the timely identification of kidney function worsening, considerably reducing the risk of an abrupt onset of acute kidney injury. Serum creatinine remains the most popular and used biomarker for assessing kidney function worldwide. However, during pregnancy the physiological hyperfiltration significantly influences plasma creatinine concentration, especially during the first trimester; even the physiological hemodilution, originating from the maternal plasma volume expansion, significantly contributes to the reduction of creatinine plasma levels. Creatinine clearance is considered the standard method for assessing glomerular filtration during pregnancy; however, creatinine tubular secretion and the inaccuracy in 24-h urine collection considerably affect results reliability. In addition, to avoid the urine retention in the dilated collecting system due to the physiological hydronephrosis during pregnancy, women should rest theoretically on their left side for one hour before starting and completing the 24-h urine collection. As a result, creatinine clearance is cumbersome and time-consuming, and can be performed only in selected, critical cases. The utilization of serum biomarkers-based equations for the estimation of glomerular filtration rate is strongly discouraged during pregnancy. Cystatin C is an effective biomarker for predicting gestational diabetes mellitus and preeclampsia but less effective for mirroring kidney function, being affected by extra-renal factors especially during the third trimester. Albuminuria is crucial for the early diagnosis and monitoring of gestational diabetes and hypertension. The measurement of urine albumin is by far more desirable than that of urine total proteins, being the latter affected by various analytical drawbacks; the first morning void urine specimen is recommended for the accurate measurement of albuminuria, and results should be expressed as albuminuria to creatininuria ratio, to minimize the intra-individual variability. In conclusion, plasma creatinine and albuminuria should be considered the most appropriate laboratory tests for the early identification and monitoring of kidney dysfunction during pregnancy.

BIBLIOGRAFIA