18 - urine

gross appearance

color

yellow → urochrome pigment

color affected by concentration

red/red-brown → RBCs, hemoglobin, myoglobin

yellow-brown, yellow-green → bilirubin

clear → normal

cloudy → cellular debris, crystals, mucus

odor

ammonia odor → urease-producing bacteria

chemical properties

specific gravity

total solute concentraiton in urine

use refractometer

chemical properties should be evaluated in context of USG → protein

check before giving treatment

PH

normal: 5.0-7.5 → affected by diet, acid-base

acidic urine → meat, acidosis, protein catabolism

alkaline urine → UTI, plant diet, postprandial, alkalosis

protein

small amounts normal in dogs → not cats

evaluate with USG → proteinuria w/minimal urine sediment = glomerular disease

glucose

renal threshold 180-220 (dog), 200-280 (cats)

causes: diabetes, stress/excitement, CKD, tubular disease, tubular injury

ketones

normally neg

test strip identifies acetoacetate, acetone → not beta-hydroxybutyrate

causes: diabetic ketoacidosis, starvation, glycogen storage disease, low carb diet, persistent hypoglycemia

occult blood

highly senseitive

differentiate between intact RBCs, Hb, and Mb

Hb → IMHA, DIC, splenic torsion, heat stroke

Mb → rhabdomyolysis (epilepsy), crush injury

RBCs → normal if <4/hpf

bilirubin

conjugated

low renal threshold in dogs → normal to see small amount

IMHA, liver/biliary disease, fever, starvation

leukocyte esterase

pyuria

low sensitivity in dogs

low specificty for cats

normal if <4/hpf

sediment

RBCs

occasional = normal

WBCs

occasional = normal

inflammation or infection → does not localize unless casts are present

casts = renal origin

epithelial cells

squamous → urethra, vagina

transitional cells → renal pelvis, ureter, bladder

casts

molds of renal tubules

form in ascending loop of henle and distal tubule

normal = granular casts, hyaline casts

renal disease = lots of granular/hyaline casts, cellular casts

hyaline

normal in small amounts

Tamm-Horsfall/albumin

dissolve in alkaline/dilute urine

seen with exercise, fever, renal disease

granular casts

coarse or fine

degeneration of other casts, protein precipitate

other

white cells → infection

renal epithelial cell → acute tubular necrosis, pyelonephritis

eaxy → end stage granular casts → intrarenal stasis

organisms

normal urine = sterile

can have no bacteria even iwth UTI

crystals

no clinical evidence of contribution to stone formation

acidic

uric acid/urates

calcium oxalate

    dihydrate = princess cut

    monohydrate = ethylene glycol

cystine

ammonium biruate

basic

struvite/triple phosphate = coffin

calcium phosphate

calcium carbonate

amorphous phosphate

ammonium biurate

microbiology

cystocentesis ideal for culture

voided has greatest potnetial for contamination → neg culture = no UTI

catheter sample can get urethral flora or induce UTI