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Part 6: Pediatric Peritoneal Dialysis |
Pediatric Nephrology and Dialysis Unit,1 Clinica Pediatrica De Marchi, Fondazione IRCCS OM Policlinico, Mangiagalli e Regina Elena, Milano, and Department of Pediatrics,2 Università Cattolica del Sacro Cuore, Roma, Italy
Correspondence to: A. Edefonti, Pediatric Nephrology and Dialysis Unit, Clinica Pediatrica De Marchi, Fondazione IRCCS OM Policlinico, Mangiagalli e Regina Elena, Via Commenda 9, Milano 20122 Italy. aedefonti{at}hotmail.com
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ABSTRACT |
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 TOP ABSTRACT INDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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Abnormalities of nutrition status are a common problem in children on
peritoneal dialysis (PD) and a source of significant morbidity and mortality.
The state of decreased body protein mass and fuel reserves (body protein and
fat mass) common in PD patients is now better known as protein–energy
wasting (PEW).
Protein–energy wasting is a slow, progressive process in chronic
kidney disease. The correct approach to this problem includes measurement of
early, intermediate, and late markers of PEW, and consideration of the risk
factors specific to the patient and to PD.
The earliest markers of PEW are associated with some symptoms observed
clinically: a decrease in dietary intake and an increase in inflammatory
markers. The second stage in the development of PEW (patients with established
PEW) is characterized by abnormalities in numerous markers: bioimpedance
analysis (BIA) and anthropometric indices, other indices of body mass and
composition, biochemical parameters, and indices of protein, glucose, and
lipid metabolism. When PEW is established, clear clinical signs become
evident: patients in this stage are characterized by high rates of
hospitalization and an increased risk for morbidity and mortality as compared
with patients without cachexia.
Risk factors for PEW can already be present in an apparently
well-nourished child who initiates PD: glucose absorption from PD fluid,
abdominal distension from PD volume, gastroesophageal reflux, and even more
importantly, inadequate dialysis dose in relation to decline in residual renal
function.
Given the complexity of the pathogenesis and clinical picture of PEW, no
single measure, but rather panels of nutritional measures are necessary to
diagnose the condition. Combined nutrition scores such as the
anthropometry–BIA nutrition score may add value to the monitoring of
nutrition status in children on PD.
KEY WORDS: Children; malnutrition; nutrition status; protein–energy wasting.
Abnormalities of nutrition status are a common problem in children on chronic peritoneal dialysis (PD) and a source of significant morbidity and mortality.
Large controversies exist concerning the correct definition of the abnormalities of nutrition status usually found in patients with chronic kidney disease (CKD). An expert panel of the International Society of Renal Nutrition and Metabolism (ISRNM) proposed that normal nutrition status be defined as maintenance of normal body composition (and, in children, growth). They recommended that the term "protein–energy malnutrition" (PEM) be reserved to cases with low nutritional intake. The term that is now preferred for abnormalities of nutrition status in CKD is "protein–energy wasting" (PEW), which indicates a state of decreased body protein mass and fuel reserves (body protein and fat mass); "cachexia" indicates the severe form of PEW (1).
The main problems in the assessment and monitoring of nutrition status in children on PD are best choice of indices of nutrition status, risk factors for malnutrition, and best means of reliably diagnosing PEW.
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INDICES OF PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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EARLY MARKERS OF PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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With regard to clinical observation of symptoms, change in appetite is
common evidence and an important warning in children on PD, especially when
linked with gastrointestinal problems (nausea, vomiting, constipation,
gastroesophageal reflux in infants), gagging, swallowing difficulties, and
fatigue. Anorexia has received much attention in the last few years because of
the knowledge that appetite and food intake are regulated by complex molecular
mechanisms at the brain level, where various hormonal stimulations arrive from
the gastrointestinal tract, fat tissue, and the pancreas. To summarize, in CKD
patients anorexigenic peptides such as leptin, insulin, and alpha melanocyte
stimulating hormone increase, and orexigenic peptides such as neuropeptide Y,
agouti-related peptide, and ghrelin decrease. Furthermore, high
proinflammatory cytokine levels—tumor necrosis factor 
(TNF) and interleukins 1 (IL-1) and 6 (IL-6)—suppress appetite
through the same central mechanism.
It is therefore not surprising that a decline in dietary intake is one of earliest markers of PEW. Dietary assessment performed by a dietician evaluating a 3-day dietary diary is a powerful means of detecting early development of PEW. Alternatively, normalized protein catabolic rate (nPCR) is an useful indicator of protein intake in patients in steady state. Chadha and colleagues (2,3) reported that nPCR declines in parallel with decline in creatinine clearance, and that nPCR is already significantly decreased when creatinine clearance is 50 – 25 mL/min/1.73 m2. Also, in adolescents on hemodialysis, nPCR is significantly decreased in those with weight loss of more than 2% for at least 3 months as compared with those without persistent weight loss.
Given those data, the guidelines from the U.S. National Kidney Foundation Kidney Disease Quality Outcomes Initiative (K/DOQI) recommend evaluation of dietary intake by means of dietary assessment or nPCR calculation every month in children under 2 years of age and every 3 – 4 months in older children (4).
The third early marker of PEW is an increase in inflammatory markers, such
as high-sensitivity C-reactive protein (hsCRP), IL-6, IL-1, and TNF.
The role of inflammation in the pathogenesis of PEM and PEW has repeatedly
been demonstrated in adults on PD, but few data in children have been
reported. Sylvestre and colleagues showed that the prevalence of high CRP
levels in children on PD is higher than that of low serum albumin, which has
long been considered a strong marker of malnutrition
(5).
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INTERMEDIATE MARKERS OF PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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The BIA technique is simple and particularly suited to clinical practice for the longitudinal follow-up of nutrition status (6,7). The measured parameters (resistance and reactance), and those directly calculated (phase angle and distance), can be compared with those of a reference pediatric population. Alternatively, it is possible to plot BIA vector on a pediatric reference chart. In a third approach, various equations have been proposed to estimate total body water and fat-free mass from BIA indices, but various limitations make these equations unreliable in clinical practice.
Data from children on PD show that BIA may be more sensitive than other commonly used methods (anthropometry, for instance) in detecting early alterations in body composition. But the limitations of BIA should be carefully taken into account when interpreting BIA indices; primarily, all BIA indices reflect both hydration and nutrition.
The anthropometric indices are well known and used largely in the assessment of body composition: weight, supine or standing height, height velocity, body mass index, head circumference, mid-arm circumference, skinfold thickness, mid-arm muscle circumference (MAMC), arm muscle area (AMA), and arm fat area (AFA). Published data for children on PD have clearly demonstrated that these indices significantly worsened in malnourished children as compared with children with a normal nutrition status, indicating that anthropometry can discriminate between well-nourished patients and those with PEW (8). Furthermore, it is worthy of note that the ISRNM expert panel (1) included MAMC among the criteria for a diagnosis of PEW in adults with CKD.
The main limitations of parameters derived from skinfold thickness are their poor reproducibility and high degree of inter-observer variability, because minimal variations in direct measurements lead to large differences in derived parameters. The key recommendation is therefore that the measurements be taken by the same person and at regular intervals (7).
As far as the biochemical indices of PEW are concerned, these include visceral liver-derived proteins (serum albumin, pre-albumin, retinol-binding protein, transferrin, ferritin), creatinine (and creatinine kinetics), leukocyte count, standard biochemistry (hemoglobin, bicarbonate, cholesterol), and inflammatory markers (CRP, hsCRP).
Serum albumin is a very strong predictor of poor outcome in adults, but it is also a very strong negative acutephase reactant, more closely associated with comorbidities than with nutrition status per se. Moreover, fluid overload and urinary and dialysate protein losses may result in hypoalbuminemia. Serum albumin values correlate with risk of dialysis initiation: as shown by Wong et al. (9), this risk increases by 54% for every 1 g/dL of serum albumin reduction.
In a study of 43 children treated with PD, serum albumin, creatinine, and hemoglobin were significantly lower in children with PEW than in those without PEW (8).
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LATE MARKERS OF PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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RISK FACTORS FOR PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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Other risk factors for the development of PEW in a well-nourished patient include younger age, duration of CKD and PD, acute and chronic inflammatory diseases, and the presence of comorbidities. Risk factors specific to PD include bioincompatible dialysis fluids, peritonitis and exit-site infections, and physical inactivity because of diurnal abdominal distension.
In a recent study, younger age, longer dialysis duration, and younger age at dialysis initiation were associated with a worse nutrition status in children on PD. In particular, the anthropometry-BIA nutrition score decreased and the percentage of malnourished patients increased in parallel with duration of dialysis, suggesting that younger children and those with a longer dialysis vintage should be strictly monitored for early markers of malnutrition (8).
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DIAGNOSIS OF PEW |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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In 2000, the K/DOQI guideline concluded that no single measure, but rather panels of nutrition measures were necessary for diagnosing PEW. In particular, the same guideline suggested that markers of protein and energy intake, markers of visceral protein pools, and markers of body mass and body composition should all be taken into account when assessing the nutrition status of patients with CKD (4).
In 2006, the ISRNM expert panel (1) stated that a diagnosis of PEW should rely on low values of serum albumin, pre-albumin, or cholesterol; reduced body mass (low or reduced body mass and fat mass, weight loss with reduced intake of protein and energy); and reduced muscle mass (muscle wasting or sarcopenia, reduced MAMC). To more objectively take into account several indices of nutrition for PEW, combined nutrition scores were developed. The well-known subjective global assessment is widely used in adults on renal replacement therapy, but cannot be applied in children as is.
Our group developed a nutrition score based on 9 parameters derived from anthropometry and BIA ("ABN score"): height, weight, BMI, MAMC, AMA, AFA, reactance, phase angle, and distance (8). Normal values, obtained from a reference pediatric population, vary from 10.3 to 15; PEW values vary from 10.3 (mild PEW) to 3 (severe PEW). The application of the ABN score in children treated with PD in 7 Italian pediatric nephrology centers showed that about 50% of children presented some degree of PEW, from mild (35%) to severe (2.3%) (8). This example is one of the few in the literature of an integrated diagnostic approach to PEW and cachexia.
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CONCLUSIONS |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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REFERENCES |
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TOPABSTRACTINDICES OF PEWEARLY MARKERS OF PEWINTERMEDIATE MARKERS OF PEWLATE MARKERS OF PEWRISK FACTORS FOR PEWDIAGNOSIS OF PEWCONCLUSIONSREFERENCES |
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
