APPROACH TO A PATIENT WITH SUSPECTED KIDNEY DISEASE

APPROACH TO A PATIENT WITH SUSPECTED KIDNEY DISEASEELIZABETH ROMANO-SEBASTIAN MD FPCP FPSN

A 28 yo female came to your clinic for bi pedal edema of 2 weeks duration. PE showed puffy eyelids, pale conjunctiva, + friction rub, decrease breath sounds and Gr 2 pedal edema. She denies any intake of any meds.

Creatinine2.4 mg/dl

ELECTROLYTESNa – 138K – 5.5iCal – 4.8Phos – 3

URINALYSIS

ColorNormal:pale to dark depending on the concentration of the

urine. Pathologic conditions:

gross hematuria hemoglobinuria myoglobinuria (pink, red, brown or black) ;

jaundice (dark yellow to brown);chyluria (white,milky) massive uric acid crystalluria (pink)

Drugs: rifampin (yellow-orange to red; phenytoin (red), nitrofurantoin (brown);

metronidazole, imipinem, methyldopa (darkening on standing)

OdorPungent

UTI due to production of ammonia)

Sweet ketones

Musty pku

TurbidityUsually transparent but can be due to inc concentration of any particle

FOAMIndicates the amount of protein in the urine

Chemical Analysis Dipstick

pHHemoglobinGlucoseAlbuminLeukocyte esteraseNitratesBilirubinSpecific gravity

pHpresence of H+ ions due to the secretion of acid in the collecting ductlow ph:

metabolic acidosis, high protein meals, (generate more acid and ammonia) and with volume depletion- aldosterone is stimulated resulting in acidic urine)

high ph:RTA, vegetable diets, infection with urease + like proteus)

Range: 5-8.5

Hemoglobin

Pseudoperoxidase activity of the heme moiety of Hgb, which catalyzes peroxide and chromagen ---colored productFalse positive:

hemoglobinuria from intravascular hemolysismyoglobinuria from rhabdomyolysishigh concentration of bacteria with enterobacter staphylococci, strep

False negative: ascorbic acid

RBC- Hematuria – blood in the urineDifferentiated by centrifugation

GlycosuriaUsed for testing

Multistix – glucose oxodase reactionClinitest – modified Benedict’s test for reducing substances

Types of glycosuriaOverflow glycosuria – above 180mg/dlRenal glycosuria – associated with Fanconi Syndrome

ProteinPhysiologic

Daily production – 40-150 mg/day40% albumin, 40% tissue, 15% Ig and fragments, 5% other plasma proteins 150 mg/24 hrs adults, 140 mg/m2 in childrenMethod is sensitive to albumin

First morning Random protein crea ratio (same time for follow-up)Types of Proteinuria

Overflow – contains Bence-Jones proteins, myoglobin, HgbGlomerular permeability

Selective - albuminNon-selective

Tubular – decrease reabsorption of filtered protein; caused by antibiotics, heavy metalsHemodynamic – caused by CHF, heat, seizures, exercise

Parameter False Positive False NegativeSpecific Gravity Reduced when in the presence

of glucose, urine pH>6.5Increased when in the presence of keto acids,

protein >7g/LpH Reduced when in the presence

of formaldehyde

Hemoglobin Ascorbic acid, delayed examination, high density of

urine, formaldehyde (>0.5 g/L)

Myoglobin, microbial peroxidise, oxidizing agent,

HCl

Glucose Ascorbic acid, bacteria Oxidizing detergents, HCl

Albumin Ig light chains, tubular proteinuria, globulins,

abnormally colored urine, HCl

Urine pH >9, quaternary ammonium detergents,

chlorhexidines, polyvinylpyrolidone

Leukocyte esterase High density of urine, high Vitamin C intake, protein >5g/L , glucose >20g/L,

cephalosporin,

Oxidizing detergents, formaldehyde (>0.4 g/L), sodium azide, abnormally colored urine due to beet

Nitrites No vegetables in diet, short bladder incubation time,

vitamin C, bacteria that do not reduce nitrates to nitrites

Abnormally colored urine

Microscopic Examination

Sediment OverviewTechnique for preparation and examinationMorning specimen is the most concentratedCentrifugation done in a conical tube for 3 to 5 minutes at 3000-5000 rpm Pipetting

Decant supernatant liquidPipette while invertedAspirate buttonMay resuspend if too thick

Cover slip: avoid bubbles, examine periphery for formed elements

ExaminationScan entire entire field at low powerMagnify selected areasStop down diaphragm or move light source for contrastStain if necessary

Microscopic Formed elementsCellular elements

WBC- easiest to find due to granular cytoplasm and lobulated nucleus

Marker for upper or lower tract infectionsIn women may be found as contaminantMay also be GN, Interstitial nephritis

RBCChanging the focus, causes red cells to appear as black tires, appear concave

NormalDysmorphic RBC’sCrenated RBC- occurs in hypertonic urineAcanthocytes- doughnut-like with blebs (mickey mouse ears)Discocyte→echinocytes→stomatocyte- transition inducible in changes in pH, osmolality and protein concentrations

CastsCan only come from the tubulesPrimarily Tamm- Horsfall mucoproteinSecreted in TAL as monomersPolymerized into casts in distal tubules and collecting ductsIncorpotate material that is within the tubulesFavored by low flow rates, low pH, high luminal NaLarger casts from larger tubules especially with decreased flows

Hyaline castFine granular cast

Broad coarsely granular castFatty cast

Waxy cast

Acute Tubular Necrosis

RBC Cast-

indicative of Glomerular injury

White Blood cell castAcute interstitial nephritis,

acute pyelonephritis, proliferative glomerulonephritis

Casts Main Clinical associationHyaline Normal subject and renal diseaseHyaline granule Normal subject and renal diseaseGranular Renal diseaseWaxy Renal insufficiency and rapidly progressing renal

diseaseFatty Marked proteinuria, nephritic syndromeErythrocyte Glomerular bleeding, proliferating/ necrotizing

glomerulonephritisHemoglobin Same as erythrocytic cast + hemoglobinuriaLeukocyte Acute interstitial nephritis, acute pyelonephritis,

proliferative glomerulonephritisEpithelial Acute tubular necrosis, acute interstitial nephritis,

glomerulonephritisMyoglobin RhabdomyolysisBacteria/ Fungi Bacterial/ fungal infection in kidney

pH 6Sg 1.02Protein ++++RBC 8/hpfWBC 9/hpfEpithelial cells manyRBC casts, fine granular casts

USGSizeCortical thicknessEchogenicityCalyxesUreter

Normal sized kidneys with hypoechoic parenchyma

54 yo male known hypertensive, known diabetic admitted for decreasing urine output

A 32 yo male known to have a solitary functioning R kidney came in for R flank pain radiating to the R testicle with no urine output for the past 8 hours

TAKE HOME MESSAGESHistory and PE will determine the type of exams to be requestedIn approaching a patient with elevated creatinine, the first step is to differentiate acute from chronic kidney diseaseTrend of creatinine more important than a single determinationProper collection of urine must be emphasized to a patientBe systematic in interpreting laboratory results.