**1. Introduction**

#### **1.1 Medical nutrition therapy**

Medical nutrition therapy (MNT) is an individualized nutrition evidence-based process that aims at treating and managing medical conditions. MNT comprises comprehensive nutrition assessment, diagnosis, specialized therapies, diet modifications, and nutrition counseling [1, 2].

A Renal Dietitian/Nutritionist, Registered Dietitian Nutritionist (RDN), a nutrition professional, or an international equivalent does the comprehensive nutrition assessment, including anthropometric measurements, nutrition-focused physical findings, monitoring and evaluating appetite, dietary intake, body weight changes, and biochemical data. This also assesses the effectiveness of MNT [3]. Renal replacement therapy significantly affects nutrition status, which in turn affects the wellbeing of the patients. Malnutrition is common among patients undergoing RRT, with more undernutrition leading towards those undergoing hemodialysis, while

overnutrition may also be found among patients on peritoneal dialysis (PD) and post-transplant patient in the chronic phase. Malnutrition is common among patients with end-stage renal disease, with a prevalence ranging from 18 to 75% for patients on hemodialysis [4]. Patients often do not take adequate calories due to dietary restrictions, which is most common with hemodialysis, and reduced appetite caused by uremia. Other factors that cause malnutrition are loss of nutrients during RRT through dialysis membrane, metabolic acidosis, inflammation, as well as the catabolic effects of RRT [5].

#### **1.2 Nutrition assessment**

Comprehensive nutrition assessment, including but not limited to a history of dietary intake, appetite, body weight and body mass index (BMI), other anthropometric measurements, biochemical data, and nutrition-focused physical findings, is required. This should be done at least within the first 90 days of starting dialysis and monitored regularly. Nutrition assessment is the first step of the nutrition care process; therefore, doing it correctly will ensure appropriate intervention. A combination of screening tools and laboratory parameters is recommended [6].

For patients on maintenance hemodialysis (MHD) and PD, it is reasonable to measure body weight and composition at least monthly and at least quarterly for transplant patients to monitor for any changes. The routine anthropometric measurements include waist circumference, skin fold measurements, and creatinine kinetics. Although BMI should be used routinely for its usefulness in predicting mortality, it should not be used in isolation because it is not sufficient to diagnose Protein-energy wasting (PEW) unless it is less than 18 kg/m<sup>2</sup> . Rather, percent change in the usual body may be more reliable for determining the risk of PEW [3].

The comprehensive nutrition assessment will inform the nutrition intervention prescribed. Based on the treatment plan, the renal nutritionist or international equivalent should therefore monitor key nutrition care outcomes, such as dietary nutrient intake, body composition, and serum biomarker levels, after which the plan will be re-assessed and adjusted accordingly to achieve the goals established. The Renal Dietitian will work with the multidisciplinary renal team throughout the nutrition care process. The patient and/or caregiver will be educated on dietary recommendations based on individual needs. Studies show that nutrition education effectively increases patients' compliance with dietary prescriptions [7].

The use of a combination of tools is recommended, including the global subjective tool (SGA) and malnutrition inflammation score (MIS).

When determining the energy requirements, the RDN should consider some factors, including but not limited to RRT modalities, level of physical activity, age, sex, weight status, disease-specific determinants, metabolic stressors, treatment goals, and the patient's overall health status. Studies suggest that diet therapy may aid in lowering dialysis doses to be used safely and effectively even as the glomerular filtration rate continues to decline [8].
