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Assessment of glomerular filtration rate (GFR) is fundamental to clinical practice, public health, and research. The kidney has several critical functions; GFR is used as an overall assessment of these kidney functions. GFR is used to diagnose, stage, and manage chronic kidney disease (CKD); ascertain the prognosis for chronic kidney disease-related events and mortality; and determine drug dosages. GFR is the rate at which the glomerulus filters plasma to produce an ultrafiltrate and can be assessed from clearance or serum levels of filtration markers. Clearance measurements using exogenous filtration markers are difficult to perform in routine clinical practice, so GFR is more commonly estimated through equations based on serum concentrations of endogenous filtration markers, most commonly creatinine. These GFR estimates are reasonably accurate, but optimal care for patients may require a confirmatory test for a more accurate GFR assessment. Confirmatory tests currently available include cystatin C-based equations, urinary or plasma clearance of exogenous filtration markers, or urinary clearance of creatinine. Appreciation of the concept of GFR and methods for optimal assessment in routine practice or special circumstances, and their strengths and limitations, are critical in making judicious use of the available tools.

Although still uncommon, pregnancy frequency in women on maintenance hemodialysis therapy has increased in the past 20 years. Most published reports suggest that intensified hemodialysis regimens result in better pregnancy outcomes. The small number of patients investigated in all reported series is the main limitation of the available studies.Retrospective case series.Data for all pregnancies that occurred in 1988-2008 in women undergoing maintenance hemodialysis (52 pregnancies) at the São Paulo University Medical School (São Paulo, Brazil).We analyzed maternal and fetal outcomes of 52 pregnancies, as well as their relationship with various clinical, laboratory, and hemodialysis parameters, such as pre-eclampsia, pregnancy before or after dialysis therapy, hemodialysis dose, polyhydramnios, anemia, and predialysis serum urea level. In addition, logistic regression models for a composite adverse fetal outcome (perinatal death or extremely premature delivery) and linear regression models for birth weight were built.87% overall rate of successful delivery, with a mean gestational age of 32.7 +/- 3.1 weeks. Pre-eclampsia was associated with a poor prognosis compared with pregnancies without pre-eclampsia: a successful delivery rate of 60% versus 92.9% (P = 0.02), extremely premature delivery rate of 77.8% versus 3.3% (P0.001), lower gestational age (P0.001), and birth weight (P0.001). Patients with an adverse composite fetal outcome had a higher frequency of pre-eclampsia (P0.001), lower frequency of polyhydramnios (P = 0.03), lower third-trimester hematocrit (P = 0.03), and higher predialysis serum urea level (P = 0.03). The same results were seen for birth weight.Retrospective data analysis. The absence of creatinine clearance measurements did not allow evaluation of the impact of residual renal function on fetal outcome.Outcomes of pregnancy in women undergoing hemodialysis often are good. Pre-eclampsia, third-trimester hematocrit, polyhydramnios, and predialysis serum urea level are important variables associated with fetal outcome and birth weight.