Antihypertensive and antiproteinuric efficacy of ramipril in children with chronic renal failure

Add-on therapy with angiotensin II receptor 1 blocker in children with chronic kidney disease already treated with angiotensin-converting enzyme inhibitors

The standard renoprotection is based on the inhibition of the renin-angiotensin system (RAS) by angiotensin convertase inhibitors (ACEi) or angiotensin II receptor 1 blockers (AT1B). The aim of our study was to analyze the effects of the addition of AT1B to ACEi-based renoprotection in children with chronic kidney disease. We examined 11 children with a mean age of 10.5 years (range, 0.5-18 years) with a mean glomerular filtration rate (GFR) of 61+/-61 ml/min/1.73 m(2). In four patients, the primary renal disease was hemolytic uremic syndrome, in three congenital nephrotic syndrome (CNS), in two reflux nephropathy, prune-belly syndrome in one and acute cortical necrosis in one. All patients were treated with complex hypotensive ACEi-based therapy. AT1B losartan was added in a mean dose of 0.9 mg/kg/day. The change in GFR, proteinuria and blood pressure at two 12-month intervals before and after adding AT1B was compared. The results showed that during the 12 months preceding AT1B therapy, there was no change in blood pressure and proteinuria, but the GFR declined in 7 of 11 patients. After the 12th month of add-on therapy with AT1B, there was a significant decrease in both absolute and indexed blood pressure values. Proteinuria decreased in eight patients, did not change in one and increased in two, including one with CNS. The GFR stabilized or increased in eight patients and decreased in three patients with CNS. In 7 of 11 patients, there was a significant, but not threatening increase in serum potassium. In conclusion, add-on renoprotection with AT1B added to ACEi is safe and significantly improves the renoprotective effects of ACEi treatment in children with progressive nephropathies, including patients with advanced CKD.

Prevalence of mutations in renal developmental genes in children with renal hypodysplasia: results of the ESCAPE study

Renal hypodysplasia (RHD) is characterized by a reduced nephron number, small kidney size, and disorganized renal tissue. A hereditary basis has been established for a subset of affected patients, suggesting a major role of developmental genes that are involved in early kidney organogenesis. Gene mutations that have dominant inheritance and cause RHD, urinary tract anomalies, and defined extrarenal symptoms have been identified in TCF2 (renal cysts and diabetes syndrome), PAX2 (renal-coloboma syndrome), EYA1 and SIX1 (branchio-oto-renal syndrome), and SALL1 (Townes-Brocks syndrome). For estimation of the prevalence of these events, an unselected cohort of 99 unrelated patients with RHD that was associated with chronic renal insufficiency were screened for mutations in TCF2, PAX2, EYA1, SIX1, and SALL1. Mutations or variants in the genes of interest were detected in 17 (17%) unrelated families: One mutation, two variants, and four deletions of TCF2 in eight unrelated patients; four different PAX2 mutations in six families; one EYA1 mutation and one deletion in two patients with branchio-oto-renal syndrome; and one SALL1 mutation in a patient with isolated RHD. Of a total of 27 patients with renal cysts, six (22%) carried a mutation in TCF2. It is interesting that a SIX1 sequence variant was identified in two siblings with renal-coloboma syndrome as a result of a PAX2 mutation, suggesting an oligogenic inheritance. Careful clinical reevaluation that focused on discrete extrarenal symptoms and thorough family analysis revealed syndrome-specific features in nine of the 17 patients. In conclusion, 15% of patients with RHD show mutations in TCF2 or PAX2, whereas abnormalities in EYA1, SALL1, and SIX1 are less frequent.

Cardiovascular disease in children with chronic renal failure

Cardiovascular disease (CVD), including atherosclerosis, hypertension, myocardial infarction, and cerebrovascular accidents, constitutes an important cause of morbidity and mortality in adults with chronic kidney disease (CKD). However, evidence has been accumulating over the past several years that children and young adults with CKD also experience significant cardiovascular complications. Studies in the United States and Europe have shown that CVD is a leading cause of death in young adults diagnosed with CKD in childhood. Risk factors include hypertension, dyslipidemia, anemia, and abnormal calcium-phosphorus metabolism, all of which are present in many children with CKD. Although improved control of uremia and treatment of traditional and nontraditional cardiovascular risk factors have proved to be beneficial in adults with CKD, no such data exist for children. The NIH is currently conducting a large-scale, prospective observational study of children with CKD that should help to elucidate the role of CVD in the progression of CKD in children and what interventions might reduce the risk of cardiovascular complications in these young patients.

Time to screen for proteinuria?

Screening for proteinuria in childhood is performed in some countries but remains a controversial subject. During the last decade, a greater understanding of the importance of proteinuria for the long-term prognosis of children with renal diseases has been gained. Exciting new data also show that proteinuria is a prognostic factor for long-term cardiovascular outcome.

CONCLUSION

In my opinion, there are still not strong enough reasons to support the routine screening of healthy children for proteinuria.

Profiling proteinuria in pediatric patients

This study was designed to characterize proteinuria in children with kidney disease. Random urine samples from 250 pediatric patients were examined by quantitative measures of total protein (pr), albumin (Alb), and creatinine (cr). Patient diagnoses were subjectively categorized as "Glomerular" (GD) or "Tubulo-interstitial" disease (TD) in origin. Proteinuria was quantitated by the random urine protein-to-creatinine (Upr/cr) ratio, and glomerular proteinuria was assessed as the albumin-to-creatinine ratio (Ualb/cr) and percentage albuminuria (%Alb=Alb/pr*100). The non-albumin fraction (1-Alb/pr) includes low-molecular-weight proteins and micro- and macroglobulins. Of the 250 patients, 112 (45%) had GD and 138 (55%) had TD. Both proteinuria and albuminuria correlated with a decline in glomerular filtration rate (GFR) (r=-0.4; p<0.0001). Those with GD averaged significantly greater %Alb than those with TD at all levels of proteinuria (p<0.0001). With loss in GFR, %Alb increased significantly in patients with TD (18+/-13 to 47+/-30%; p<0.001) and GD (56+/-26 to 74+/-15%; p<0.01), respectively. The %Alb at all levels of GFR averaged <50% in those with TD and >50% in those with GD. In conclusion, random Ualb/cr, Upr/cr, and %Alb provide a simple and inexpensive assessment of proteinuria and may profile renal disease activity and response to therapy in pediatric patients.

Treatment of primary and secondary hypertension in children

The incidence of pediatric hypertension (HTN) is increasing, mainly due to an increase in primary (essential) HTN, or PH. There are only a limited number of studies assessing the characteristics and treatment efficacy of PH versus secondary HTN (SH). We conducted a retrospective analysis of 158 pediatric patients (mean age: 10.8 years; sex ratio: 51.1% female, 48.9% male) with HTN of whom 34.4% had PH and 65.6% had SH. The vast majority were either African-American or Caucasian. Among all patients, therapy induced a significant decrease in systolic blood pressure (SBP) and diastolic BP (DBP) (both p<0.0001). SBP (p<0.0001) and DBP (p=0.002) declined significantly in PH patients. PH and SH patients with a body mass index (BMI) >95th percentile (%) had a significantly higher post-therapy SBP (both p<0.05) than those with a BMI <95th%. SBP declined similarly in PH patients treated with calcium-channel blockers (CCB) and angiotensin-converting enzyme inhibitors (ACEI). DBP declined only in PH patients treated with ACEI. SBP and DBP (both p<0.0001) declined significantly in SH patients. Post-therapy BP was similar in SH patients treated with either CCB or ACEI. Post-therapy SBP and DBP were significantly lower in SH patients than in PH patients; moreover, therapy induced a greater decline in SBP and DBP in the SH patients. Compared to PH patients, SH patients were twofold more likely to achieve a SBP less than the 95th% after therapy. We conclude that (1) significant lowering of BP with either CCB or ACEI is achievable in most children with HTN, and (2) SH patients respond better to therapy than those with PH.

Left ventricular geometry in children with mild to moderate chronic renal insufficiency

Left ventricular hypertrophy (LVH) is the most important independent marker of cardiovascular risk in adults with chronic kidney disease. Cardiovascular morbidity seems increased even in children with chronic renal insufficiency (CRI), but the age and stage of CRI when cardiac alterations become manifest are unknown. For assessing the prevalence and factors associated with abnormal LV geometry in children with CRI, echocardiograms, ambulatory BP monitoring, and biochemical profiles were obtained in 156 children aged 3 to 18 yr with stages 2 through 4 chronic kidney disease (GFR 49 +/- 19 ml/min per 1.73 m2) and compared with echocardiograms obtained in 133 healthy children of comparable age and gender. LV mass was indexed to height2.7. Concentric LV remodeling was observed in 10.2%, concentric LVH in 12.1%, and eccentric LVH in 21% of patients. LVH was more common in boys (43.3 versus 19.4%; P < 0.005). Probability of LVH independently increased with male gender (odds ratio [OR] 2.62; P < 0.05) and standardized body mass index (OR 1.56; P = 0.01). Low hemoglobin, low GFR, young age, and high body mass index were independent correlates of LV mass index (0.005 < P < 0.05). LV concentricity (relative wall thickness) was positively associated with serum albumin (P < 0.05). Probability of abnormal LV geometry increased with C-reactive protein >10 mg/dl (OR 26; P < 0.001). In conclusion, substantial cardiac remodeling of both concentric and eccentric type is present at young age and early stages of CRI in children. Prevalence of LVH is related to male gender, anemia, and ponderosity but not to BP. Additional effects of volume status and inflammation on cardiac geometry are also evident.

Epidemiology of pediatric chronic kidney disease

In contrast to the adult population, in whom a variety of registries have confirmed the incidence, prevalence, and diagnoses associated with chronic kidney disease (CKD), the epidemiological information on pediatric CKD is currently imprecise and flawed by methodological differences between the various data sources. Obstructive uropathy and congenital aplasia/hypoplasia/dysplasia are responsible for almost one half of all cases of CKD in children, underscoring the fact that a substantial percentage of the pediatric CKD population develops renal insufficiency very early in life. However, there are distinct geographic differences in the reported causes of CKD, in part because of environmental, racial, genetic, and cultural (consanguinity) differences. Furthermore, despite apparently comparable incidence rates, high mortality in countries that lack health care resources results in a low prevalence of CKD in those locations. In countries where renal replacement therapy is readily available, the most favored treatment modality is renal transplantation in all pediatric age groups. Additional efforts to define the epidemiology of pediatric CKD worldwide in a more uniform manner are necessary if a better understanding of the full extent of the problem, areas for study, and the potential impact of intervention is desired.

Hypertension in children with chronic kidney disease

Hypertension occurs commonly in children with chronic kidney disease (CKD) and undoubtedly contributes to the progression of disease. This review summarizes the role of hypertension in the progression of CKD in children and highlights the central role played by the renin-angiotensin system in this relentless process. Strategies for reno-protection are discussed, and treatment recommendations are made for control of hypertension in this patient population.

Clinical research in pediatric nephrology: state of the art

The goals of clinical research include comparing new and standard treatments, establishing treatment efficacy, defining risk factors for disease, elucidating pathophysiologic mechanisms of disease, and establishing causation. Although the randomized clinical trial has been the "gold standard" in clinical research and is the strongest study design to establish causation for many clinical research questions, an interventional study or "experiment" such as a randomized trial is often not possible. Observational study designs also demonstrate associations between exposures and outcome. To determine whether these associations are likely to be causal, one can assess a number of qualities, first outlined by the British epidemiologist Sir Austin Bradford Hill. These qualities include analogy to what is known; the plausibility, strength and specificity of the association; consistency and coherence across studies; the temporality of the putative cause and effect; and the presence of a biological gradient. The presence of these factors adds weight to the probability that a given association is causal. Systematic reviews and meta-analyses use these factors in combining studies to assess whether associations are cause and effect. Additionally, new methods in the analysis of longitudinal data collected in observational studies can help to determine causation. In this review, we will use recent literature and contemporary topics in pediatric nephrology to illustrate state-of-the-art research methods using classic epidemiological elements needed to establish causation.

The role of calcium antagonists in patients with chronic renal failure

The objective of antihypertensive treatment in patients with chronic renal failure, many of whom have elevated blood pressure levels, is to reduce cardiovascular events and to slow down the progression of kidney function impairment. Calcium antagonists have been shown to be effective and safe antihypertensive drugs in patients from different age groups, including children. On the basis of numerous studies, one may conclude that the main benefit of antihypertensive therapy is because of the blood pressure lowering effect per se and that calcium antagonists do not differ from other antihypertensive drugs in the ability to prevent cardiovascular complications of hypertension. In particular, calcium antagonists are not inferior to other groups of antihypertensive agents in the prevention of coronary artery disease. There is, however, now evidence from controlled clinical trials that drugs interfering with the renin-angiotensin system are more beneficial than other antihypertensive agents in patients with chronic renal failure. Thus, several studies have demonstrated that ACE-inhibitors and, in patients with type-2 diabetic nephropathy, AT 1-antagonists are superior to other classes of antihypertensive drugs, including calcium antagonists, in delaying the progression of renal insufficiency. Therefore, in hypertensive patients with chronic renal failure antihypertensive treatment should be initiated with a drug that inhibits the renin-angiotensin system.

Ultradian but not Circadian Blood Pressure Rhythms Correlate with Renal Dysfunction in Children with Chronic Renal Failure

Whereas the diurnal fall of BP (dipping) is an important prognostic marker in patients with chronic renal failure (CRF), the integrity of physiologic ultradian (i.e., shorter than 24 h) cardiovascular rhythms in patients with CRF is unknown. Also, the relationship between conventional dipping analysis and Fourier spectral rhythm analysis has not been examined in renal hypertension. The prevalence and dimensions of the circadian and three ultradian (12, 8, and 6 h) cardiovascular rhythms were studied by ambulatory BP monitoring in 214 children (aged 3 to 18 yr) with CRF (stage 2 to 4 chronic kidney disease) and no antihypertensive treatment compared with 938 healthy control subjects, and the relationship of rhythm characteristics to conventional dipping parameters, renal function, proteinuria, and serum electrolytes was assessed. The CRF cohort exhibited significantly reduced amplitudes of the circadian and all ultradian cardiovascular rhythms studied (all P < 0.01). Moreover, all BP and most heart rate rhythms showed significantly delayed acrophases (time of peak; P < 0.01). Whereas conventional BP dipping parameters (day/night difference, day/night ratio) and the 24-h BP amplitude were independent of renal function, the 8-h BP amplitude was positively correlated with GFR (r = 0.3, P = 0.01) and inversely correlated with the urinary protein/creatinine ratio (r = -0.27, P < 0.05), and the 6-h BP amplitude was inversely correlated with proteinuria (r = -0.3, P < 0.02). Children who displayed 24- or 12-h cardiovascular rhythms had significantly lower serum calcium levels than children without these rhythms. In summary, children with CRF display not only blunted circadian but also blunted ultradian cardiovascular rhythms. Ultradian but not circadian rhythms or conventional dipping parameters are quantitatively associated with renal function and proteinuria.