Renal Disease Clinical Nutrition Assessment and Intervention Fall 2024 PDF

Renal Disease LECTURE 6 CLINICAL NUTRITION ASSESSMENT AND INTERVENTION FALL 2024 1 1 Physiology & Function v Gross Anatomy o Bean-shaped organs...

Renal Disease LECTURE 6 CLINICAL NUTRITION ASSESSMENT AND INTERVENTION FALL 2024 1 1 Physiology & Function v Gross Anatomy o Bean-shaped organs o Size of a fist o Retroperitoneal cavity; located near the middle of the back, just below the rib cage, one on each side of the spine o Blood supply: renal artery v Histology o Cortex: external portion o Medulla: internal portion o Nephron: functional unit § Each kidney consists of ~1 million functioning nephrons § Consists of glomerulus connected to series of tubules § Each nephron functions independently & contributes to final urine § When a segment of nephron is destroyed, that nephron is no longer functional 2 2 1  3 3 Physiology & Function vGlomerulus o Spheric mass of capillaries surrounded by membrane (Bowman’s capsule) o Glomerular filtration à production of ultrafiltrate § Kidneys receive 20% of cardiac output, filtering ~1600L/day of blood § Produce ~180L of ultrafiltrate; production of ultrafiltrate mainly passive, relies on perfusion pressure generated by heart, supplied by renal artery § Blocks blood cells and proteins v Tubules o Segments: Proximal convoluted tubule; Loop of Henle; Distal tubule; Collecting duct o Tubular re-absorption à production of urine § Active process of re-absorption and secretion in tubules (re-absorb most components of ultrafiltrate: amino acids, glucose, selective minerals, water) § 1.5L urine excreted in average day; results in fluid and electrolyte balance, balance of organic solutes, excretion of most end products of metabolism v Urine à collecting tubules à renal pelvis à ureter à bladder 4 4 2  5 5 Physiology & Function v Main functions of kidneys: o Maintain homeostasis § Fluid, pH, electrolyte balance o Continuous filtration of blood o Excretion of metabolic end products o Production of enzymes and hormones v Regulation of fluid: kidney regulates fluid with vasopressin o ↑ excess of body water (low osmolality) → ↓ vasopressin secretion → ↑ excretion of water o ↑ osmolality → ↑ vasopressin secretion → ↑ retention of water 6 6 3  Physiology & Function v Additional functions of the kidneys o Blood pressure control: renin-angiotensin mechanism o Produces erythropoietin (EPO) that stimulates marrow production of RBCs § Deficiency of EPO factor in severe anemia present in chronic renal disease o Produces the active form of Vitamin D § Active vitamin D promotes efficient absorption of calcium by gut, and is one of the substances necessary for bone remodeling & maintenance § Active vitamin D also suppresses PTH production, which is responsible for mobilization of calcium from the bone § Maintenance of calcium-phosphorus homeostasis involves complex interaction of parathyroid hormone (PTH), calcitonin, active vitamin D; gut, kidney, bone § Factor in secondary osteoporosis o Aids in elimination of both calcium and phosphorous 7 7 Nephrolithiasis v Kidney stones o Formation: supersaturation of compounds, then crystalization o Within kidney and downstream in the ureter o Most important risk factor is low urine volume o Increased rates of nephrolithiasis associated with obesity, diabetes, metabolic syndrome, family history § Most frequent occurrence during 30s and 40s § More frequent in men than women - Overall prevalence of kidney stones 8.8% - 7.1% in women; 10.6% in men v Types of stones o Calcium stones are most common: 60% of stones are calcium oxalate, 10% calcium oxalate and calcium phosphate, 10% calcium phosphate o Uric acid: 5-10%; associated with type 2 diabetes o Struvite stones: 5-10%; mostly associated with UTI in women o Cystine stones: 1-2%; tend to form in those with cystinuria (genetic disorder) 8 8 4  9 9 Kidney Stones: MNT v Knowledge of type of stone will help direct MNT v Uric acid stones o Low urine pH can contribute; goal: maintain alkaline urine pH (6.2-6.8) o Low purine intake may be beneficial (purine à uric acid) § Uric acid is an end product of purine metabolism § ~1/2 purine load is from endogenous sources (ie tissue catabolism) § Exogenous dietary sources accounts for remainder § Examples: organ meats, anchovies, herring, sardines, meat-based broth, gravy, roe, scallops, mussels, mackerel vStruvite stones o Form in presence of bacteria: Pseudomonas, Klebsiella, Proteus mirabilis o Recurrent UTIs o Because of infectious origin: diet has no definitive role § Except avoidance of urine alkalinization § Cranberry juice can lower urine pH o Medical management: surgical removal, shockwave lithotripsy 10 10 5  Kidney Stones: MNT v Calcium stones o Dietary calcium: no restriction, adequate intake § Previously thought low calcium would help prevent calcium stone formation § Has since been demonstrated foods high in calcium can have protective effect o One explanation: ↓ calcium intake à ↑ intestinal oxalate absorption à ↑ urinary super-saturation of calcium and oxalate § Dietary intake does not ↑ stone formation & restriction may à osteoporosis o Oxalate restriction (calcium oxalate stones) § ↓ rhubarb, spinach, strawberries, chocolate, wheat bran and w/w products, almonds, peanuts, pecans, beets, tea (green, black), high doses of turmeric o Limit (have moderate amounts of) animal protein, more fruits and vegetables o ↓Sodium; urinary calcium increases as urinary sodium increases o ↑Potassium (consider low oxalate K+ fruit/veggies) 11 11 Kidney Stones: MNT v High fluid intake should be focus for all types of stones o May need to drink 3 L/day, fluids should be taken in divided doses v Moderate protein intake, emphasis fresh fruits and vegetables o Alkaline Ash Diet 12 12 6  Lab Values in Kidney Disease Creatinine Creatinine is a waste product that is made Reference Range: when your body breaks down protein when ↑ Creatinine 0.6-1.5mg/dL muscles are injured. Degradation of phosphocreatine. A high serum (blood) creatinine level could mean kidney damage. BUN is a measure of wastes (urea) in the BUN blood. ↑ BUN may mean ↓ kidney function. Reference Range: As BUN ↑ and becomes extremely high, 6-20mg/dL symptoms may appear: bad taste in the ↑ BUN mouth, poor appetite, nausea, vomiting. Other factors may affect BUN: Bleeding in intestines, CHF, certain medications may make BUN higher than normal. 13 13 Lab Values in Kidney Disease GFR Flow rate of filtered fluid through the kidney. Range: Provides estimate of functioning nephrons. ↓ GFR 90-120 mL/min GFR (Glomerular Filtration Rate) gives an idea of the speed at which kidneys are failing. GFR Description 90-130 ml/min Kidney damage, but normal kidney function 60-89 ml/min Mild decrease in kidney function 30-59 ml/min Moderate decrease in kidney function 15-29 ml/min Severe decrease in kidney function Less than 15 ml/min Kidney failure, end stage renal disease (ESRD) < 50 ml/min: ≤ 20% kidney function 14 14 7  Lab Values in Kidney Disease *Albumin in Urine *Serum Albumin Inside healthy kidneys, Inflammatory biomarker nephrons filter out wastes but keep in large molecules (RBC ----- Albumin and ALB). Some kidney diseases damage nephrons Serum ALB 50% should be HBV protein (may differ with dialysis) Energy Based on cause of AKI, stress, nutrition status Potassium 50% high biologic value (HBV) protein Phosphorous (mg/day) Individualized, or 4.6 mg/dL or ↑ PTH) Potassium (g/day) Individualized No restriction unless >5.0 mg/dL, if K↑ then 35kcal/kg may 30-35kcal/kg *upper ibw be indicated in some cases) Phosphorus (mg)