Introduction and Approach to Nephrology

INTRODUCTION AND APPROACH TO NEPHROLOGY BY Dr: Husam Alazzani Functional anatomy and physiology 1. Structure Proximal (convoluted) tubule Glomerulus Early distal (convoluted) tubule Late distal tubule Cortex Medulla Pars recta Thin descending limb Thin ascending limb Cortical collecting duct Thick ascending limb Medullary collecting duct Loop of Henle mechanism 1. 2.function Lumen Blood Na reabsorption (%, hormonal control) Water permeability A Proximal N a^ + 3N a^ + 3N a^ + - 2 K^ + 65% Highly permeable N a^ + ( c .a.)^ * Angiotensin II Sympathetic nerves Peritubular forcest 'Shunt' B Thick ascending limb N a^ + 201 K ^ + K ^ + 2 K^ + 25% Impermeable C a^ 2+ N a^ + ,K^ + , M g^ 2+ C Early distal N a^ + H ^ + H ^ + Cr 3N a^ + 2 K^ + 3N a^ + 6% Impermeable C a^ 2+ C * a ^ (2 + 1) D Late distal/cortical collecting N a^ + Principal cell K ^ + 3N a^ + 2 K^ + 2-3% Aldosterone Permeability increased by ADH Intercalated cell Symptomes of renal disease 1. Loin pain 2.dysurea 3. Frequency and urgency 4.Pricipitancy 5.Strungury 6. Hesitensy 7. Drippling 8. Hematurea 9.Polyurea 10.Oligourea 11.Anurea 12.Nacturea 13.Urine incontinence 14. Urine retention 15. Uretheral discharge 16. Edema 17.Renal colic 18.Fever Signs of renal disease Appearance earthy face Hypertension Astraxis M.cramp Restless leg Nails Muehrckes nail Leuconychia Mees nail Terry nail Tophy Hyperventlation Raised JVP PERICARDIAL RUB pulmonary edema Anemia Uremic frost Drowssiness and coma Investigation of renal disease A. Functional 1. GFR Biochemical marker for kidney function .creatinine .urea .cystatin C 2.URINE ANALYSIS .dipstick .microscopy continue B.STRUCTURAL 1 plane radiography and contrast radiography(anterograde, retrograde and execration uro,urtro or cystography) 2.ultrasonography 3.CT SCAN 4.MRI 5.cystoscopy 6. biopsy C.STRUCTURAL AND FUNCTIONAL RADIONICLUTIDE STUDY 6:0 continue D. investigation to determine systemic cause and results of renal dysfunction A. Functional investigation 1. GFR How to estimate GFR? Normally 75_115 ml\min in female 95_145 ml/min in male Clinical Evaluation of Kidney Function TABLE 1. Methods for Estimating Kidney Function Method Serum Creatinine Applications Most frequently used assessment of kidney function Serum Cystatin C More accurate in older persons and patients with cirrhosis due to low muscle mass More accurate in those with an increase in muscle mass Sensitive to mild changes in GFR Chronic Kidney Disease Epidemiology (CKD-EPI) Collaboration Equation CKD-EPI Creatinine Variables include serum creatinine, age, race, and gender More accurate than MDRD and CGE equations in older persons and in those with GFR >60 mL/min/1.73 m² CKD-EPI Cystatin C Variables include serum cystatin C, age, and gender Can be used as confirmatory test for CKD May be more accurate than creatinine-based equation in those with muscle wasting, chronic illness, or high muscle mass CKD-EPI Creatinine-Cystatin C Equation uses same variables as CKD-EPI creatinine but different exponents and includes serum cystatin C Creatinine-cystatin C combination provides the most accurate eGFR in most patient populations Modification of Diet in Renal Disease (MDRD) Study Equation Variables include serum creatinine, age, race, and gender Similar accuracy as CKD-EPI when eGFR is 15-60 mL/min/1.73 m² Creatinine Clearance (CrCI) Variables include serum and urine creatinine and 24-hour urine volume Useful in pregnancy, extremes of age and weight, amputees, malnourished and cirrhotic patients (situations where creatinine is low, so CKD-EPI and MDRD will overestimate GFR) Cockcroft-Gault Equation (CGE) Variables include serum creatinine, body weight, age, and gender Improved accuracy when age is <65 years Radionuclide Kidney Clearance Scanning lothalamate GFR scan or diethylenetriamine pentaacetic acid (DTPA) GFR scan Useful in kidney donor evaluation if eGFR is borderline for donation or other times when accurate prediction is essential DTPA can be used for determination of relative (differential) function of each kidney (e.g., prenephrectomy) B.Urine analysis Clinical Evaluation of Kidney Functio TABLE 2. Findings on Urinalysis Normal Range Dipstick Specific gravity PH 1.005-1,030 5.0-6.5 Blood/heme pigments None Protein None to trace Glucose None Ketones None Leukocyte estera None Nitrites None Microscopic Erythrocytes 0-2/hpf Leukocytes 0-4/hpf Squamous epithelial cells <15/hpf Casts None or hyaline TABLE 3. Urine Crystals Type Calcium oxalate Morphology Envelope; dumbbell; needle Associated Conditions Image 4 Hypercalciuria; hyperoxaluria; calcium oxalate stones; ethylene glycol poisoning Calcium phosphate Prism; needle; star-like clumps Distal renal tubular acidosis; urine pH>6.5; tumor lysis syndrome; acute phosphate nephropathy Uric acid Rhomboid; needle; rosette, barrels; hexagonal plates Hyperuricemia; gout; diabetes mellitus; obesity; tumor lysis syndrome; urine pH <6.0 Struvite (magnesium ammonium phosphate) Coffin-lid Alkaline urine due to chronic urinary tract infection with urease-producing organisms Cystine Hexagonal Cystinuria TABLE 4. Definitions of Proteinuria and Albuminuria Total Urine Protein Urine Collection Method Normal Clinical Proteinuria 24-Hour excretion <150 mg/24 h ≥150 mg/24 h Spot urine protein-creatinine ratio <50 mg/g=≤150 mg/24 h ≥150 mg/g=>150 mg/24 h Urine Albumin Urine Collection Method Normalb Moderately Increased Albuminuriab.c Severely Increased Albuminuriab.c 24-Hour excretion <30 mg/24 h 30-300 mg/24 h >300 mg/24 h Conventional spot urine dipstickd Negative Negative Positive Albumin-specific spot urine dipstick <3.0 mg/dL 23.0 mg/dL Positive Negative Positive Spot urine albumin-creatinine ratio <30 mg/g =<30 mg/24 h 30-300 mg/g-30-300 mg/24 h >300 mg/g =>300 mg/24 h