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Prof. Dr. Reto NeigerSmall Animal Clinic

University of Giessen, Germany

Urologyfrom Greek οὖρον ‐ oûron, "urine" and ‐λογία, ‐logia"study of" is the medical and surgical specialty that focuses on the urinary tracts of males and females

Testing for urology casesUrine (± urine culture)Routine blood testsGFR measurementDiagnostic imaging

Radiographs (± contrast)UltrasoundEndoscopyMRI / CT

Biopsy

Urine collectionMid‐stream voiding (cats: non‐absorbable litter)

Contamination from urethra etc.Not advised for cultureGood to test for haematuria

Manual bladder expressionUse mainly in anaesthetised patients

CatheterisationMale dog: pre‐measure length, no force; good for all purposes including urine cultureFemale dog: dorsal recumbency, use speculumTomcats: extend penis caudallyFemale cats: anaesthesia required, ventral recumbency

Urine collectionCystocentesis

Under palpation, blind, underultrasound controlAdvantage: no contamination, easyto perform, well tolleratedDisadvantage: may introduce micro‐haematuria, puncture other organs, dissemination of transitional cellcarcinoma (?)Contraindication: <20‘000 PLT/µl

UrinalysisPerform as quickly as possible after collection (< 30 min)Use minimum of 3 ml urineIf refrigerated – warm before analysisRecord type of collection

Colour and transparencySpecific gravity (refractometer) Dip‐stick analysisSedimentBacterial cultureOthers

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Physical propertiesUrine colour

Derived fromurochromes

TransparencyNormally clearCloudy: mostlyWBC, casts, crystalls

OdorAmmonia odordue to bacteria

Urine specific gravity: 3 methods

Urine specific gravityOnly refractometer gives accurate results (never usedipstick value)Measures total number of solutes and their weight

1000 mg/dl (55 mmol/l) glucose increases USG by 0.0041000 mg/dl protein increased USH by 0.003

Measure USG BEFORE any fluid or drugs are given

1.000 1.008 1.0121.030 dog1.035 cat

>1.050

isohypo normal In dehydratedanimasthenuric

Chemical propertiespHProteinGlucoseKetonesBilirubinOccult blood

USG, leucocytes, urobilinogen, others not useful in dogs and cats

Warm urine after refrigerationUse centrifuged urineUse proper timing: normally 1 minute after drop has been appliedKeep strips air‐tightAvoid desinfectant

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Urine pHNormally measured on dip‐stick but ok with any pH‐meterNormal: 5‐7.5Varies based on diet and acid‐base statusPlant based diet causes more alkaline urineCats have post‐prandial alkaline tideUTI with urease producing bacteria have alkaline urine

Protein in urineOn dip‐stick: negative, + (30mg/dl), ++ (100mg/dl), +++ (1000mg/dl)Always assess protein in relation to USG (see UPC)False positive in very alkaline, false negative in very acidic urineUrine on dipstick is commonly albuminCategorise into pre‐renal, renal and post‐renalAlways assess protein in relation to sediment result

Pre‐renal: Bence‐Jonce Protein, haemoglobinPost‐renal: UTI, neoplasia, genital disease

Urin Protein‐Creatinine ratio (UPC)Protein on dipstick dependent on urine SGTo assess urine protein excretion one needs metabolic cageUPC and 24‐h protein excretion are very closely correlated  Normal: < 0.2 (dogs and cats) (see IRIS guidelines)

Measure UPC only with inactive sediment!

Glucose in urineNormally negative in dogs and cats (all glucose reabsorbed in proximal tubule)Positive if serum glucose > renal threshold 

Dogs >180 mg/dl = 10 mmol/lCats > 240‐300 mg/dl = 13‐16 mmol/l

False positives: rarely with some drugs (antibiotics)

GlucosuriaDiabetes mellitusStress hyperglycaemia (if > threshold)i.v. glucose infusionTubular defect (Fancony, primary glucosuria, etc.)Tubular injury in severe acute kidney injury (AKI)Chronic sick catSevere urethral obstruction

Occult blood in urineDetects RBC, haemoglobin and myoglobinInterpretation: together with sediment analysis and plasma colour

HaematuriaTrauma, urolithiasis, tumour, infarction, inflammation, coagulopathy, etc

HaemoglobinuriaHaemolysis (mostly intravascular)

MyoglobinuriaCrush injury, heat stroke, seizure, grey hound myopathy, severe hypokalaemia (cats)

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OthersKetones

Acetoacetate, acetone in urine give positive results, ß‐Hydroxybuturate (other breakdown of fatty oxidation) does notMost commonly in diabetic ketoacidosis or diabetic ketosis

BilirubinFrom breakdown of excessive haemoglobin (only conjugated bilirubin in urine)In dogs + (to ++ in males) of bilirubin can be normalIn cats bilirubin is always abnormalCases: haemolysis, liver disease, post‐hepatic disease, fever, starvation

SedimentMust be done on fresh urine samples (casts and crystals might otherwise disappear)Centrifugation: 1000‐1500 rpm for 5 minutesInterpretation: knowledge of USG and way of collectionRecord all findings and amount (neg, +, ++, +++)

Casts on 10x (LPF)Cells and bacteria on 40x (HPF)Crystals (type)Others (fat droplet, sperm, artefacts and contaminants)

Cells Red blood cells: 

Numbers depend on collection technique (commonly < 5RBC / HPF)Can come from entire urogenital tractCauses: see lecture abnormal urine colour

White blood cells:Numbers depend on collection (more in voided samples) (commonly < 5WBC / HPF)Increased numbers = pyuriaIndication of inflammation in urinary or genital tract (localisation unclear). Most often UTI

CellsSquamous epithelial cells:

Common in voided and catheter samplesNo significance

Transitional epithelial cells:Arise from renal pelvis to urethraSeen in normal (few, during sampling) and abnormal samples(inflammation, trauma, FLUTD, etc.) May becomemalignant diagnosis of TCC

Renal epithelial cells:Are always abnormal (ischemia, inflammation, AKI, etc.)

CastsCylindrical moulds from lining of tubules with cellsand/or inflammatory proteins (Tamm Horsefallmucoprotein)

OrganismsUrine is sterile. Collectionmethod importantPyuria most ofter togetherwith bacteria (exceptions)UTI also possible withoutvisible bacteriaParasite eggs: 

Dioctophyma renaleCapillaria spp.

Capillaria D. renale

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CrystalsMany crystals are normal in dogs and cats (struvite, calcium‐oxalate)!Crystalluria ≠ Urolithiasis!!Crystals may dissolve or form de novo (especially during refrigeration)Crystal formation depends on pH, temperatur und osmolality

Urinary biomarkersShould demonstrate kidney injury earlyShould also show localisation of injury (Glomerulus, Tubules, both)Differentiate renal from pre‐renal/post‐renalAssess severity of injury

Proteins are normally not in urine and can be used as biomarkers

JVIM 2013:27:1001

Tubular dysfunction

Glomerular dysfunction

JVIM 2013:27:1001

Potential urinary protein biomarkerin dogsBiomarker Disease with increased valuesHigh Molecular Weight‐proteins• Albumin• Immunoglobulin G• Immunoglobulin A

Chronic kidney disease (CKD)Leishmaniasis, Leptospirosis, PyometraLeishmaniasis, Leptospirosis

LowMolecular Weight‐Proteins• Retinol‐binding protein• α1‐ and β2‐Microglobulin

CNE, urolithiasisX‐linked hereditary Nephropathy

Tubular enzymes• N‐acetyl‐β‐D‐glucosaminidase• γ‐Glutamyltransferase

Pyometra, AKIPyometra, AKI

Inflammatory proteins• Interleukin‐2, ‐8• Neutrophil gelatinase associated 

lipocalin (NGAL)

Cisplatin‐induced AKIAKI versus CKD, others

Adapted from JVIM 2013:27:1001

Routine blood testsUrea (BUN)CreatininePhosphorusTotal protein

Albumin / GlobulinElectrolytesCholesterol

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Azotaemia etc.Azotaemia = Increase in urea and creatinin

Pre‐renal azotaemia (decreased perfusion ofkideny; hypovolaemia, anaemia, heart failure, etc.)Renal azotaemia (intrinsic kidney diseasePost‐renal azotaemia (obstruction of urine flowirrespective where)

Uraemia = syndom of azotaemia with clinicalsigns (anorexia, vomiting, ulcers, bad breath, etc.)

USG

↑↑↑

↓↓↓

AzotaemiaUrea  und Creatinine

Pre‐renal Renal Post‐renal

Urea:creatinin‐ratio does not differentiate

USG USG

Liver

NH3Ureacycle

Urea

Urea

Urea

FoodProteins

NH3

Colon

Body proteins

Amino acids

KidneyUrea

Urea

Urine75%

Faeces25%

Relationship between urea and GFR in dogs with various degrees of normal or reduced kidney function

Osborne & Finco: Canine and Feline Nephrology and Urology

Abnormal ureaIncreasedPost prandial (4‐6 hoursafter protein meal)Gastrointestinal bleedingIncreased catabolism(infection, fever, ...)Certain drugs (steroids)

Decreased Low protein dietPolyuriaHepatopathy, most commonly portosystemicshuntAnabolic steroids 

Kidney

Muscle

Creatine

Creatinine

2% dailybreak down

Creatinine

Freely filtered

~1‐5% secreted

Not reabsorbed

Creatinine

Urine ‐ 100%

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Osborne & Finco: Canine and Feline Nephrology and Urology

Relationship between creatinine and GFR in dogs with various degrees of normal or reduced kidney function

Steady‐state releationship of GFR and creatinine

A=IRIS stage 1B=IRIS stage 1 and early 2C=IRIS stage 3 & 4

Ref: 0.3‐1.3 mg/dl

Discordant Results between ureaand creatinine

Disproportionate ↑ urea relative to creatinine

Disproportionate ↑ creatininerelative to urea

Severe dehydration or volume depletion (common)

Liver diseases

Gastrointestinal bleeding Anorexia or low protein diet

Emaciated animal Massive muscle injury (acute)

Young animal Well‐muscled animal

• Discordant results can not always be explained

Important factsNORMAL UREA AND CREATININE DOES NOT NECESSARILY IMPLY NORMAL KIDNEY FUNCTION

INCREASE IN CREATININE OVER TIME MAY POINT TOWARDS PROGRESSIVE LOSS OF RENAL FUNCTION EVEN IF VALUES ARE STILL WITHIN NORMAL LIMITS

Routine blood testsPhosphorusTotal protein

Albumin / GlobulinElectrolytesCholesterol

Phosphorus: filtered in glomeruli andreabsorbed in tubulus. >85% nephron loss to seeincreased phosphorusAlbumin normally not excreted via kidney;may be lost in PLNCholesterol increases in animals with nephroticsyndrome

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Serum renal biomarkersCystatin C

NGALHomocysteinBig‐endothelin‐1

Glomerular filtration rate (GFR)Definition:

Estimated clearance, defined as volume of plasma cleared of a given substance over time

Influenced by many non‐renal factors (protein intake, hydration status, sodium balance, gender, age, breed, day‐to‐day variation, etc.)

Wide reference interval of normal GFR in healthy animals

Heiene R, Moe L: Pharmacokineatic Aspects of Measurement of Glomerular Filtration Rate in the Dog: A Review. JVIM 1998Lefebvre HP, Craig AJ, Braun JP. GFR in the dog: Breed effect. Proceedings of the 16th ECVIM–CA Congress, Amsterdam, 2006

GFR measurementGFR can not be measured directlyRenal clearance of substance (x) that is neither reabsorbed nor secreted by tubules = GFRGFR = V • C(U) / t • C (P)  = ml/min

C(U) = concentration in urine (mg/ml)V= volume of urine (ml)t = specific amount of time (min)C(P) = concentration in plasma (mg/ml)

Heiene R, Moe L: Pharmacokineatic Aspects of Measurement of Glomerular Filtration Rate in the Dog: A Review. JVIM 1998Lefebvre HP: Renal Function testing In: Nephrology and Urology of Small Animals

Ideal substance to measure GFRFreely filtered in glomerulumNot reabsorbed in tubulusNot secreted in tubulusNot protein boundNon‐toxicDoes not alter GFREasily measured in plasma and urine

INULIN (fructose polymere) 

ClearanceCalculation from plasma concentration versus time 

Clearance (Clplasma)Calculation from plama and urine data

Clearance (Clrenal)

If substance is excreted solely via kidneyClplasma = Clrenal

Without tubular secretion or reabsorptionClplasma = GFR (e.g. Inulin – Clearance)

Two types of ClearanceEndogenous Clearance

Renal ‐ Clearance

Exogenous ClearancePlasma ‐ Clearance

D     = dose of marker; AUC= area under plasma concentration versus time curve

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Glomerular filtration rate (GFR)Used substances

Renal Inulin clearance (Gold Standard)Endogenous creatinine clearanceExogenous creatinine clearancePlasma Inulin clearencePlasma Iohexol clearanceRadioactive isotopes (± Scintigraphy)

Single injection without collection of urine possible

Renal inulin clearenceGold standardInject inulin i.v. (bolus or constant rate infusion)Collect urine over 24 hours (metabolic cage)Measure inulin in plasma and urineCalculate GFR based on formula

Very cumbersome, rarely performed (only research)