Sample chapter fromBSAVA Manual of Canine and FelineClinical Pathology2nd editionEdited by Elizabeth Villiers and Laura Blackwood BSAVA 2005www.bsava.com149Chapter 10 Urine analysis10Joy ArcherUrine analysisIntroductionUrineanalysisisasimple,non-invasiveandcheaplaboratory test that rapidly provides valuable informa-tion about the urinary tract and other body systems. Acompleteurineanalysis(includingdipstick,specificgravity(SG)andsedimentexamination)shouldbeperformed,evenifonecomponentpartshowsnoabnormalities. Concurrent serum or plasma biochemi-cal analysis is often required to gain maximum benefitfrom urine analysis.Free-catchsamplesshouldbecollectedintoacleancontainerwithminimalcontactofthevoidedurine with the animals body. Ideally, new clean clearcontainerswithtight-fittinglidsshouldbeprovided.Use of containers provided by owners should be dis-couraged as these can contain traces of detergents,bleach,drugs,cosmeticsandothercompoundsthatcanaffectthetests.Asepticcollectiontechniques(cystocentesis, catheterization in certain circumstances)should be used if the sample is to be cultured.HydrationstatusgreatlyaffectsSGandcertaindrugs and dietary supplements can affect results (in-cluding dipstick and sediment evaluation), so any medi-cationorsupplementationtheanimalhasreceivedshould be noted.Urineshouldbeanalysedasrapidlyaspossibleafter collection, ideally within 30 minutes. If this is notpossibleitshouldberefrigeratedimmediatelyandChanges seen in aged urine. 10.1Constituent Change CauseColour and clarity Dark and turbid RBC lysis; growth of bacteriapH Increase Proliferation of urease-producing bacteria, splitting urea to ammoniaBilirubin Decrease Broken down by sunlightCasts Disintegration Low SG; low pH; increased temperature; vigorous shaking Sediment Crystals and amorphous material Storage at low temperature; evaporation; pH changeEpithelial cells Morphological change, disintegration Low SG and osmolalityWhite blood cells Swelling, lysis, vacuolation Low SG and osmolalityRed blood cells Crenation, lysis Low SG and osmolalityBacteria Growth Long-term storage at high temperatures, especially voided samplesand in plain (not boric acid) tubesstoredforpreferablynomorethan612hoursaftercollection.Refrigeratedurineshouldbebroughttoroom temperature and thoroughly mixed before analy-sis. Urine should not be frozen if sediment analysis isto be performed. Casts are particularly vulnerable todisintegration and will only be detected if fresh urine isexamined very soon after collection. Casts may be theonly laboratory abnormality present in early renal dis-ease (prior to the development of azotaemia). Duringstorage,otherformedelementsmaychange;theremay be cellular disintegration, and urine pH may alter.Thesechangesinurinecompositionaremorepro-nounced the longer the storage time and the higher thetemperature.Inaddition,microorganismscancon-tinue to multiply whether they are present as infectiousagents or contaminants. The common changes foundin aged urine are summarized in Figure 10.1.Gross appearanceBefore beginning any analysis the urine sample shouldbe observed in a transparent container for clarity (tur-bidity) and colour, and these recorded using a consist-ent system of semiquantitative reporting. Normal urineshould be clear and yellow to straw-coloured, depend-ing on concentration of coloured pigment molecules.The interpretation of gross findings is summarized inFigure 10.2.150Chapter 10 Urine analysisSpecific gravityThe specific gravity (SG) of urine is a useful indicator ofrenalconcentratingability.Thiscanbereadilyob-tainedbymeasuringtherefractiveindex(RI)inaspeciallycalibratedrefractometer.Theinstrumentmeasures the degree through which light is bent (re-fracted) when it passes through a liquid: the amount ofrefraction (refractive index) is a function of the amountand type of solute (particles) in that liquid. RI and SGare correlated, as the SG is defined as the ratio of theweight of the liquid to an equal volume of distilled water.The SG of a solution thus depends on the number andmolecular weight (size) of particles in the solution.Urine always has an SG greater than that of distilledwater, which has an SG of 1.000. The SG of urine isincreased by large amounts of glucose, protein, lipidand contrast material.Thereisalsoareasonablycloserelationshipbe-tweenSGandosmolality.However,urineSGvarieswith the type of solute present, while osmolality does not.Osmolality depends on the number of osmotically activeparticles in solution regardless of their size (SG dependsupon both number and size) and is considered to be amore accurate assessment of renal tubular concentrat-ing (and diluting) ability than SG. However, SG is easilymeasured(refractometer),whileosmolalitydetermin-ations require a special freeze point depression osmo-meter. In dogs, it is possible to calculate approximateosmolalityfromurineSG:multiplicationofthelast2digits of the urine SG by 36 approximates osmolality.However, this is inaccurate if the urine contains largenumbers of molecules (e.g. glucose) as these have amuch greater effect on urine SG than on osmolality.RefractometersRefractometersarecalibratedtoreadRI,SGandplasma protein. Many refractometers compensate forchanges in temperature between 15 and 37C. Mostare calibrated for use with human samples, althoughinstruments for veterinary use are available. The latterhave one calibration scale for dogs and large animalurine (which is similar to a scale for human urine) andaseparatescaleforcaturine.Human-basedinstru-mentswillslightlyoverestimatetheSGofcaturine.CareoftherefractometerissummarizedinFigure10.3. Urine SG can be determined by some dipsticksby a chemical method but this is unreliable in veterinarypatients and is not recommended.Changes in colour and clarity of urine.RBC = red blood cells; WBC = white blood cells.10.2Appearance CauseClear, very pale straw Low SG (very dilute urine)colourClear to slightly turbid, High SG (concentrated urine)deep yellowBright red Fresh blood (unoxidized)Red Free haemoglobin/lysed RBCRedbrown Older (oxidized) haemoglobin/lysed RBCDark redbrown MyoglobinTransfusion of haemoglobin-basedoxygen-carrying solution (Oxyglobin)Redpink Consumption of beetroot or red fooddyesDark yellow/greenish BilirubinOrangeyellow Tetracycline group of drugsCloudy Increases in any constituents: Cells WBC RBC Epithelial cells Casts Mucus Bacteria Amorphous material/crystalsCare of the refractometer. ddH2O = doublydistilled water.10.3 Rinse and dry the clear optical surface after each use Regularly check the zero setting with double distilled water(ddH2O): SG 1.000 Check accuracy of calibration with 5% NaCl solution in ddH20:SG 1.022 Use it within the temperature range of calibration (1537C) Avoid scratching/damaging the optical surfaceUrine specific gravity and osmolality ranges. 10.4Condition SG Osmolality(mOsm)Usual range in healthy dogs 1.0151.045Usual range in healthy cats 1.0351.060(May vary outside theseranges depending on fluidintake and hydration status)Possible range 1.0011.080Hyposthenuria 300Interpretation of resultsSG in health will vary with the state of hydration andfluid intake. Under normal conditions urine SG rangesbetween 1.015 and 1.040 in healthy dogs and between1.036 and 1.060 in healthy cats. Details of SG rangesand osmolality are shown in Figure 10.4.SG should be measured in conjunction with dipstickanalysis.Whenthereisamarkedincreaseinurineglucose or protein content, SG will be increased and thiscould lead to the assumption that the animal has betterconcentrating ability than it actually has. Interpretation ofurineSGvaluesrequiresknowledgeofotherpara-meters, e.g. water intake, drug therapy, clinical condi-tion and haematological and biochemical parameters.151Chapter 10 Urine analysisSG is a valuable test for evaluating kidney dilutingand concentrating ability, as the loss of concentratingability is amongst the first signs of renal tubular disease. SG values >1.030 in the dog and >1.035 in thecat are indicative of adequate renal concentratingability and, if found in an azotaemic animal,would indicate prerenal azotaemia. Isosthenuric urine in an azotaemic animalindicates intrinsic renal failure. SG values between 1.015 and 1.030 (dog) or1.035 (cat) indicate that some urineconcentration has occurred but do not confirmadequate renal concentrating ability and so, in anazotaemic animal, would suggest early renalfailure (see Chapter 11). SG values persistently less than 1.020 supportthe presence of polyuria and consequentpolydipsia.The approach to differentiation of causes of alteredurine SG is summarized in Figure 10.5.Common causes of low urine SG andpolyuriaRenaldysfunctionisanimportantcauseofpolyurialeading to isosthenuria, and is discussed in Chapter 11.Differentiation of common causes of altered urine specific gravity. 10.5SG Clinical findings Other laboratory changes Causes>1.030 dog Dehydration Urea, protein, albumin, packed cell Plasma hyperosmolality causing increased water retention>1.035 cat volume (PCV), Na+by the kidney1+ in dilute urine Glomerulonephritis or amyloidosis leading to protein-losing nephropathyHaemorrhage (see text)Genital tract secretionsBilirubin Negative in cats; trace or Trace/1+ or above in cats Haemolytic anaemia1+ in dogs with SG >1.025; 2+ or more in dogs Hepatobiliary disease (especially cats)2+ in dogs with SG >1.040Blood Negative Positive Haematuria (see Figure 10.15)Haemoglobin Negative Positive Intravascular haemolysis (e.g. immune-mediated haemolytic anaemia)Myoglobinuria (due to muscle damage)Urobilinogen Negative Positive Not clinically helpful in haematological or hepatobiliary disease in dogsand cats. Bilirubin more usefulNitrites Negative Not reliable in animals due to uncontrollable urine retention time in thebladder with frequent false negativesLeucocyte Negative Not sensitive enough to detect inflammation (urinary tract infection (UTI))esterase in animals. Need to check urine sediment for leucocytes154Chapter 10 Urine analysisCauses of alkaline urine include: Feeding: this results in transiently alkaline urineas a result of the postprandial alkaline tide whichoccurs when secretion of gastric acid causes arelative alkalosis Urinary tract infection with urease-producingbacteria, such as Proteus or Staphylococcus;these break down urea to ammonia, resulting inalkaline urine Metabolic and respiratory alkalosis; these resultin reduced hydrogen ion (H+) excretion into urine(see Chapter 9) Urinary retention (e.g. due to obstruction); thismay result in decomposition of urea to ammonia Contamination by detergents or disinfectants.If urine is persistently alkaline and artefacts havebeen ruled out, urine culture and sediment examina-tion should be performed.Causes of decreased pH, i.e. acidic urine, include: Metabolic and respiratory acidosis, leading toincreased H+ excretion Vomiting: paradoxical aciduria with metabolicalkalosis may occur in hypochloraemic vomitinganimals. Vomiting results in loss of hydrochloricacid (HCl) and also potassium (K+). In the kidneysodium (Na+) is resorbed in the tubules where itis usually exchanged for K+, which is excreted.Na+ may be reabsorbed with chloride (Cl) orbicarbonate (HCO3). Since both K+ and Cl are inshort supply due to the vomiting, Na+ is resorbedwith HCO3, resulting in more acidic urine Hypokalaemia: increased renal resorption of K+ isaccompanied by increased excretion of H+.GlucosuriaGlucose is freely filtered then reabsorbed in the proxi-mal tubule, but resorptive capacity is limited. Glucos-uriaoccurswhenbloodglucoseexceedsthisrenalthreshold,forexampleindiabetesmellitusorasaresult of stress in cats (fructosamine is useful to distin-guish stress and diabetes, see Chapter 16). The renalthreshold in dogs is 10 mmol/l and is slightly higher incats (1417 mmol/l).Glucosuria in the absence of hyperglycaemia re-flectsatubularresorptiondefectinwhichtherenaltubulesfailtoreabsorbglucosefromtheglomerularfiltrate. Fanconi syndrome and primary renal glucos-uriaareexamplesoftubulartransportdefectsthatoccur in dogs (see Chapter 11).KetonuriaInsmallanimalsketonuriaisusuallyassociatedwithdiabeticketoacidosis(DKA),althoughitmayalso be seen in starvation. It is important to note thatdipsticks detect acetoacetate and, to a lesser extent,acetone,butdonotdetectbetahydroxybutyrate(BHB). During the initial stages of insulin therapy forDKA there is increased conversion of BHB to aceto-acetate and so the degree of ketonuria may initiallyappear to increase.ProteinuriaAsmallamountofproteinmaybenormalbutthedipstick result should be interpreted with knowledge ofthe urine SG, as the significance of the result is relatedto the concentration of the urine. For example, a 3+protein dipstick result in urine of SG 1.008 indicates amuch greater protein loss than the same 3+ protein inurineofSG1.045.Proteinuriamayresultfromglomerulonephropathy,tubulartransportdefects,orinflammation or infection within the urinary tract. Haem-orrhagemustbemarked(macroscopicratherthanmicroscopic)beforeitcausessignificantproteinuria(Vadenetal.,2004).Thussedimentexaminationisimportant in the evaluation of proteinuria.Urine protein:creatinine ratioIf there is no evidence of inflammation in the sedimentornogrosshaematuria,theurineprotein:creatinineratio (UPC) can be used to quantify proteinuria (Figure10.8).Thequantityofproteinlostisrelatedtotheamount of creatinine in the urine to correct for variationin urine SG. This is possible because the excretion ofcreatinine is relatively stable for an individual and thereis essentially no tubular reabsorption in dogs and cats.Urine total protein and creatinine are measured on thesamesamplebyautomatedchemicalmethods,re-ported in the same units and a ratio obtained:Urine protein:creatinine ratio (UPC) = Urine protein (mg/dl) Urine creatinine (mg/dl)UnitsmayneedtobeconvertedfromSIunitstoperform the calculation:Protein (g/l) x 100 = Protein (mg/dl)Creatinine (mmol/l) x 1000/88.4 = Creatinine (mg/dl)Interpretation of urine protein:creatinine ratio.This should not be measured in urine when10.8UPC Significance2.0 Significant proteinuria>5.0 Indicative of glomerular disease especiallyglomerulonephritis and glomerular basementmembrane damage/protein-losing nephropathy>8.012.0 Frequently associated with amyloidosisinflammation or gross haematuria is present in the sediment.The type of glomerular disease present cannot bedetermined from the UPC and biopsy and histology arerequired for a definitive diagnosis and prognosis. (SeeChapter 11 for further discussion on proteinuria.)UPC should not be measured or interpreted in urinethat contains >100 white blood cells in the sediment orif there is evidence of gross haematuria, since thesemay cause an increase in the urine total protein andgiveafalselyelevatedUPC.Thiscanbeabovetherange that indicates the presence of glomerular loss.155Chapter 10 Urine analysisN.B. Microscopic haematuria has little impact on theUPC, and only gross haematuria leads to significantalteration of the ratio (Vaden et al., 2004).Albumin and globulinThe dipstick mainly detects albumin and is insensitiveto globulin or Bence Jones proteins (light chain frag-mentsofimmunoglobulinwhichmaybepresentinurine of animals with multiple myeloma (see Chapter7)). Albumin, globulin and Bence Jones proteins are alldetected using the sulphasalicylic acid (SSA) method:when SSA is added to urine, proteins are denaturedand form a precipitate which makes the sample turbid.The turbidity can be assessed visually or more accu-rately using spectrophotometry, comparing the sampleturbiditywiththatofasetofstandards.TheSSAmethod is not widely used in commercial laboratories.MicroalbuminuriaPersistentmicroalbuminuria(MA)isanindicatorofglomerular damage associated with early progressiverenal disease in humans. Such low level albumin loss isnot detected by routine dipstick analysis. Recently new,very sensitive, separate dipsticks for urine microalbuminhave become available for use in dogs and cats. Theseare immunological tests using a monoclonal antibodyspecific for canine or feline albumin. Studies have shownthat 2025% of healthy dogs and 13% of healthy catshave MA, whilst approximately 40% of dogs and catswithamedicalconditionhaveMA(Jensen2001;Wisnewskietal.,2004).TheprevalenceofMAin-creases with age (Radecki et al., 2003). Diseases thathave been associated with MA include cardiovasculardisease,urogenitaldisease,dentaldisease,airwaydisease, pyoderma, inflammatory bowel disease, hyper-thyroidism,hyperadrenocorticism,diabetesmellitus,infectious diseases and neoplasia (Grauer et al., 2001;Vaden et al., 2001;Pressler et al., 2003; Wisnewski etal., 2004). Prednisolone therapy may also lead to MA.Thus it appears that a significant proportion of normalanimalsandanimalswithdiseasesunrelatedtotherenal system may have MA. It is not clear at this timewhat proportion of animals with MA will develop renaldiseaseorprotein-losingnephropathy.Animalswithend-stage renal disease may test negative for MA. Thediagnostic usefulness of this test is still under evaluation.BilirubinuriaThere is a low renal threshold for bilirubin and even smallincreases in plasma bilirubin can lead to bilirubinuria.Thus bilirubinuria is detected prior to hyperbilirubinae-miaorjaundice.Bilirubininurineisintheformofconjugated bilirubin, since unconjugated bilirubin is boundtoalbumin,whichdoesnotusuallypassthroughtheglomerular barrier in significant amounts unless glomeru-lar disease is present. Bilirubinuria is not seen in healthycats but a small amount of bilirubin may be found in theurine of normal dogs (see Figure 10.7). This is in partbecause they have a very low renal threshold, and in partbecause canine renal tubular cells are able to catabolizehaemoglobin to unconjugated bilirubin, conjugate it andthen secrete it into the urine. Increased bilirubinuria maybe caused by cholestasis or haemolytic anaemia.Haematuria, haemoglobinuria andmyoglobinuriaThe dipstick pads for blood and haemoglobin both usethesamechemicalmethod,butaspeckledappear-ancetothedipstickpadisindicativeofhaematuria,whilst a diffuse colour change suggests haemoglob-inuria(ormyoglobinuria).However,adiffusecolourchange may also be seen with severe haematuria andthe pads do not reliably differentiate haematuria andhaemoglobinuria. Sediment examination is useful formaking the distinction, although red cells may lyse invitro,especiallyindiluteurine,resultinginthefalseimpressionofhaemoglobinuriaratherthanhaema-turia. True haemoglobinuria results from intravascularhaemolysis (e.g. due to immune-mediated haemolyticanaemia) and is accompanied by haemoglobinaemiaand anaemia. Haemoglobinaemia can be identified bycentrifuging a blood sample and examining the plasma(which is pink/red). Myoglobinuria is seen uncommonlyin small animals, but may result from severe muscledamage due to trauma or ischaemia (e.g. associatedwithaorticthromboembolismincats).Themuscleenzymes creatine kinase (CK) and aspartate transami-nase (AST) are usually markedly elevated in serum/plasma. Myoglobin is a small protein which is rapidlyclearedfromthecirculation,somyoglobinuriaisnotaccompanied by pigmented plasma.Urine sediment analysisThe third and perhaps most important component of acomplete routine urinalysis is the microscopic exami-nation of the sediment. A consistent volume of urineshould be used for preparing the sediment for analysis.Laboratories use volumes that vary (10 ml, 5 ml, 3 ml)to produce a semiquantitative result. Larger laborato-ries also use disposable microscope slides, with a grid,which hold a set volume of sediment (usually 0.5 ml).Experienced microscopists use unstained sedimentand a phase contrast microscope. Less confident per-sons may elect to stain the sediment before microscopyto facilitate cell identification. A regular microscope withthe condenser lowered can be used to identify cells inunstained sediment if phase contrast is not available.Themicroscopeshouldbekeptcleanandingoodworking order, with lens and condenser alignment main-tained for the best possible visible field and resolution. Ifan oil immersion (100X) objective is used for identifyingbacteria or assessing cell morphology, the lens shouldbe wiped clean after each use to prevent oil dripping intothe condenser and seeping into the objective. It is alsoadvisable to place a coverslip on the sample to protectthe objective lens from damage.A suggested method for preparation and analysis isas follows:1. Fresh urine or warmed previously refrigeratedurine should be used.2. The sample is mixed well but gently to preventcast destruction.3. A constant volume (10, 5 or 3 ml, often 3 ml isused for cat urine), is placed in a conicalcentrifuge tube.156Chapter 10 Urine analysis4. The urine is centrifuged gently (suggested 1,000rpm for 5 minutes; this will vary with the type ofcentrifuge used). If a smaller volume of urine (i.e.6.5Calcium oxalate monohydrate Very occasionally present in Ethylene glycol poisoningnormal dogs and cats Consumption of toxic plants in catsCalcium oxalate dihydrate May be present in normal Form in acid or neutral or weakly alkaline urinedogs and cats May lead to calcium oxalate calculiMay be present in ethylene glycol poisoning (but more commonly seemonohydrate form)Calcium phosphate May be present in normal Form in weak acid to alkaline urinedogs May lead to urolithiasisHypercalcaemia is predisposing factorAmmonium urate/biurate Common in Dalmatians and Uric acid crystals form in acid urineUric acid English Bulldogs Urate/biurate crystals form in alkaline urineForm in hepatic disease/portosystemic shuntsForm due to metabolic defect in DalmatiansMay lead to urate calculiBilirubin May be present in normal Form in hepatobiliary disease especially catsdogs with concentrated urine Form in acid urineCystine Absent in normal animals Form in acid urineurine Form due to a defect in tubular resorption of cystine in Bull Mastiff, English Bulldog,Dachshund, ChihuahuaLeucine/tyrosine Absent in normal animals Form in acid urineurine Form due to metabolic disease/inherited tubular diseaseCholesterol May be present in normal Form in acid to neutral urinedogs and cats May form in chronic protein-losing nephropathyAmorphous material Common in concentrated(variable content) urine and some other breeds. Large numbers of crystals indilute urine, persistent crystalluria and large crystalshave greater significance in relation to stone formation.If large numbers of calcium oxalate monohydratealong with dihydrate crystals are found in urine, inges-tionoftoxicsubstances,particularlyethyleneglycol(antifreeze)andcertaintoxicplants,shouldbesus-pected. High concentrations of these substances canbe metabolized to produce oxalates, which precipitatein the renal tubules as calcium oxalates and can causeirreversible renal failure (see Chapter 11).Unusual crystals may be formed if large quantitiesof drug or drug metabolites concentrate in urine, e.g.sulphonamide drugs frequently form crystals (Figure10.12h).Unusual,difficulttoidentifycrystalscanoftenbedrug-derived.Cholesterolcrystals(Figure10.12i) may be seen in normal animals or in nephroticsyndrome. Bilirubin crystals (Figure 10.12j) may beseenwhenthereismarkedbilirubinuria,duetocholestasisorhaemolyticanaemia,andmayocca-sionallybeseeninconcentratedurinefromnormaldogs (especially males).CellsRed and white blood cells may be seen in low numbersinnormalurine.Redcells(Figure10.14a)maybeconfused with fat droplets or yeast (Figure 10.9). Whitecells (usually neutrophils) are larger than red cells, andare round with granular cytoplasm and often an indis-tinct nucleus (Figure 10.14b). Normal urine sedimentcontains small numbers of transitional epithelial cellsfrom the bladder; increased numbers are seen second-ary to bladder inflammation/irritation. Transitional cellsarelargeandroundtooval,withacentralroundnucleusandabundantcytoplasm(Figure10.14c).Voidedurinemayalsocontainsquamousepithelialcells from the urethra and vagina which are also largebuthaveanangularpolyhedralshapeandasmallround nucleus (Figure 10.14d). A rare renal and ureteralepithelial cell may also be found. These are small witharelativelylargeroundnucleusandlesscytoplasm(Figure10.14e).Thesignificanceofincreasednum-bers of red and white blood cells and epithelial cells issummarized in Figure 10.15.Miscellaneous findingsBacteriamayreflectcontaminationorinfection;anassociated inflammatory response would support thelatter (Figure 10.16a), but is not always present. Otherorganisms, such as nematodes, yeast and fungi, mayoccasionally be identified (Figures 10.16be) and theirsignificanceissummarizedinFigure10.17.Sperm,mucus strands and cotton fibre contaminants are shownin Figure 10.16(fh).160Chapter 10 Urine analysisInterpretation of urine sediment analysis: cells. 10.15Cell type Normal findings Significance of abnormal findingsRBCs 1x105/ml If present in a free-catch sample may be contaminants which have proliferatedcocci must be present to bedetectable in urine sedimentMucin Small amount may be presentFat droplets Normal in catsSperm Normal in malesYeasts None In free-catch urine may be contaminants, thus infection should be confirmed oncystocentesis sampleInfection usually occurs only in immunosuppressed animalsFungi None Aspergillus infection usually occurs only in immunosuppressed animalsNematodes None Rare infection with Dioctophyma renale or Capillaria plica. Faecal contaminationStarch granules None ContaminantsPollen grains(a) (b) (c)(d) (e) (f)Urine sediment: miscellaneous. (a) Sediment containing degenerate neutrophils and numerous bacteriaconsistent with urinary tract infection. (Unstained.)(b) Aspergillus spp. Fungal contamination, especially in free-10.16catch and old urine, is common. (Sedistain.) (c) Alternaria spp, a contaminant especially in free-catch urine. (Sedistain.)(d) Parasite eggs can be found if there is faecal contamination of the sample or, rarely, when organisms are present in thekidney itself. (Sedistain.) (e) Mites are rare contaminants in free-catch urine. (Sedistain.) (f ) Sperm are found in entiremale dog urine. (Sedistain.) (g) Mucus strands. Variable amounts of fine material float on the surface of urine preparationsand are normal. (Sedistain.) (h) Cotton fibre common contaminant, not to be confused with casts (Sedistain.) (Originalmagnification (a) X1000, (b,c,d,e) X200, (f,g,h) X400.)(g) (h)162Chapter 10 Urine analysisUrine cytologyWhenabnormalorincreasednumbersofepithelialcells are seen on a standard sediment examination,cytological examination of a stained smear should beperformed. A fresh sample of urine should be concen-trated (preferably using a slower centifugation speed tominimize cell damage) and the sediment placed on aslide precoated with serum (to ensure attachment ofcells). The cells should be gently spread into a mono-layer and the preparation air dried before staining witha Romanowsky type stain (Wrights Giemsa or a re-lated rapid stain).ThepH,SGandageingofurinehasaprofoundeffect on cell morphology and causes swelling and lossofinternalmorphologicaldetail,sourineforspecialcytological analysis should be as fresh as possible. If adelay in making smears is anticipated, boric acid mayhelp preserve cellular morphology. However, if sam-plesaretobemailedouttoanexternallaboratory,centrifuged smears should be prepared in house when-ever possible, air dried or wet fixed with a spray fixativeand mailed along with a urine sample. Smears madefrom 24-hour-old urine are often impossible to interpretdue to cell deterioration.Normal urine sediment contains small numbers ofepithelialcells(describedabove)seensinglyorinsmall clusters. Chronic infection or inflammation re-latedtourolithiasisandcertaindrugscancauseincreased exfoliation of lining epithelial cells into theurine.Theremaybemarkedmorphologicalhyper-plastic or dysplastic changes of these cells which canexfoliate in large numbers in rafts and clusters. Therecan also be metaplastic changes in the cytoplasm dueto the chronicity of the condition (Figure 10.18a), andinsomeinstancesnuclearchangescanbeverysimilar to those seen with neoplasia. Guidance from acytologist is advisable in these situations. Numerousneutrophils may be seen in inflammatory or infectiousconditions:thesemaybeverydegenerate,some-times show loss of normal segmented nuclear mor-phologyandmaybeconfusedwithsmallepithelialcells (Figure 10.18b).Neoplastic disease of the urinary system is usuallymalignant and frequently causes haematuria. The mostcommontumouristhetransitionalcellcarcinoma.Cells from this are large and can exhibit marked aniso-cytosis and anisokaryosis as well as many other cri-teria of malignancy (see Chapter 20) (Figures 10.18cd).Lesscommontumoursareurothelialcarcinomaoradenocarcinoma,inwhichcellsareusuallysmallerwithdeeplystainingcytoplasm(Figure10.18e),andsquamous cell carcinoma, in which exfoliated cells arelarge and have cytoplasmic characteristics of keratini-zation, cytoplasmic vacuolation and nuclear changescharacteristic of malignancy (Figure 10.18f). Cells fromprimarytumoursofthekidneyepithelialcells(carci-noma) are infrequently shed into the urine. These areusually small cells with clear cytoplasm and a centralround nucleus.Rhabdomyosarcoma(botyroid)bladdertumoursare rare, but can occur in young dogs of large breeds.Leiomyomas/sarcomas may also occur in the urinarysystembutcellsfromtheserarelyexfoliateintothe(a)(d)(b)(e)(c)(f)Urine sediment cytology. (a) Clusters of epithelial cells showing squamous metaplasia which can occur inchronic conditions with irritation/inflammation. (Wrights Giemsa stain.) (b) Sediment containing a mixture of10.18bladder epithelial cells, neutrophils, erythrocytes and bacteria. If the sample was aseptically collected this would indicatepyuria urinary tract infection (UTI). This kind of sediment is some times referred to as active sediment. (Giemsa stain.)(c) Transitional cell carcinoma of the bladder. The cells exhibit many criteria of malignancy: variation in cell and nuclearsize, multinucleated cells, coarse nuclear chromatin and high nuclear:cytoplasmic ratio. (Wrights Giemsa stain.)(d) Transitional cell carcinoma of the bladder. Cells are stained with Papanicolaou stain which highlights nuclei andparticularly size and shape of nucleoli. (Papanicolaou stain.) (e) A cluster of cells from an urothelial carcinoma. The cellsare smaller than those in the transitional cell carcinoma with foamy cytoplasm and large nuclei with multiple nucleoli.(Giemsa stain.) (f) Raft of cells from a squamous cell carcinoma of the bladder. These cells are large with an angularoutline and sparse cytoplasmic vacuoles around the nucleus. (Wrights Giemsa stain.) (Original magnification (a,c,e,f)X1000, (b,d) X500.)163Chapter 10 Urine analysisurine. Renal or bladder lymphoma can result in exfolia-tion of large numbers of often abnormal lymphocytesinto the urine.Cytological diagnosis of bladder tumours is particu-larly difficult as polyps and epithelial hyperplasia mayexfoliatesimilarcells.Ifacytologicaldiagnosisofmalignant tumour is made, follow-up biopsy and histo-logy are advisable, particularly in the case of bladdermucosal tumours, to confirm malignancy and the de-gree of invasiveness of the tumour.Uroliths (calculi/stones)Uroliths(thepreferredterm)orcrystalscanbeana-lysed for mineral content using semiquantitative chemi-calanalysiskits.Thefollowingconstituentscanbemeasured: Calcium Oxalate Phosphate Magnesium Ammonium Uric acid Cystine.UrolithscanalsobeanalysedusingX-raycrystallography, polarized light microscopy and infra-red (IR) spectroscopy. These methods are preferabletochemicalsemiquantitativemineralionanalysis.Identification of crystal types and/or mineral contentisessentialforsuccessfultherapyinanimalswithrelated urolithiasis.Uroliths are believed to form more readily in super-saturated urine. However, other factors play a part: The presence of a nucleation centre or nidus(e.g. bacteria, mucin plug) Urine pH Duration of urine supersaturation Absence of crystallization inhibitors normallyproduced by bladder mucosal cells Possibly genetic factors.Riskfactoranalysisforurolithformationcanbeperformed and expressed as the relative supersatura-tion(RSS)index.TheRSSisobtainedbycomplexcomputer-based analysis of urine volume, pH and con-tent of calcium, oxalate, magnesium, uric acid, mucin,citrate and pyrophosphate. RSS were developed andare used by food manufacturers for the formulation ofdiets suitable for treatment and prevention of struvite,calcium oxalate and calcium phosphate urolithiasis inbothdogsandcats.Severalstudieshavesuggestedthat RSS can be used to predict the risk of formation ofthese uroliths. In practice, analysing urine pH and theamounts and types of crystals present can be used as aguide to which type of calculus may be likely to form, orhas formed and is present. Such analysis can also beused to monitor the effectiveness of therapy.Struvite and calcium oxalate are the most commonuroliths identified in dogs and cats but over the last 20years there has been a change in the relative propor-tion of these uroliths, with a increase in incidence ofcalcium oxalate urolithisis and a decrease in struvite(Lingetal.,2003).Thisislikelytoberelatedtothewidespreaduseofmanufacturedurinaryacidifyingdiets with restricted magnesium content. In one studyin dogs analysing urolith submissions, approximately44%werestruviteand42%werecalciumoxalate(Houston et al., 2004). Struvite were most common infemale dogs and calcium oxalate in male dogs. In cats50% of urolith submissions were calcium oxalate and44% were struvite, while the majority of urethral plugs(81%) were struvite (Houston et al., 2003).Clues to the type of urolith present are the breed,urine pH, urolith radiodensity (calcium oxalate, calciumphosphate, cystine and struvite uroliths are radiodense,whilst urates are radiolucent) and the type of crystalsseeninurinesediment.Howeverthetypeofcrystalpresent is not always the same as the type of urolith. Alltypes of uroliths in the bladder may lead to a secondaryurinary tract infection, and, if the organism producesurease, urine pH increases leading to struvite crystalformation.Struvite urolithsStruvite uroliths (Figure 10.19) may form in sterile urinethat contains high concentrations of magnesium, phos-phorus and ammonium ions and is of neutral to alkalinepH.Indogs,theyareformedmorefrequently,andmore rapidly, when there is also a co-existing infection,particularly with urease-producing bacteria (Staphylo-coccusandProteus).Thisenzymecanspliturea(abundantinurine)toproduceammoniumionsandCO2, which forms bicarbonate and increases urine pH.The ammonium ions become part of the struvite crys-tals. Increased concentrations of these ions are alsoreported to affect the mucins glycosaminoglycans pro-ducedbythebladdermucosalliningcells,reducingtheir protective ability. Struvite calculi are most com-mon in young female dogs and in the following breeds:mixedbreeds,MiniatureSchnauzers,ShihTzuandBichon Frise.Struvite stones from the bladder of a dog. 10.19In cats, struvite calculi formation is most common insterile conditions in older female cats and is less com-monly associated with infection (where there is no ageor sex predilection). In cats, struvite is also a commoncomponent of many urethral plugs which occur almost164Chapter 10 Urine analysisexclusively in male neutered cats with or without urinarytract infection (UTI). High-magnesium dry diets, alkalineurine and a reduction in urine glycosaminoglycans havebeenimplicatedinthedevelopmentofbothstruvitestones and struvite-rich plugs.Calcium oxalate urolithsCalcium oxalate uroliths form in acid to neutral urine,usuallyintheabsenceofUTI.Indogs,theyoccurmore commonly in older male animals. A breed pre-disposition for Lhasa Apso, Shih Tzu, Bichon Frise,Miniature Poodles, Miniature Schnauzers and York-shireTerriersisreported.Incats,calciumoxalateurolithsaremorecommoninmales,withnoagerestriction. Burmese, Himalayan and Persian cats arereported to be more often affected. Risk factors fortheirformationareahigh-proteindiet,increaseddietary calcium, oxalate, sodium and vitamin C. Theacidifying diets for preventing struvite formation mayalsobecontributoryinsomecases,astheyhavereduced magnesium and produce acid urine. A pos-sible inherited mechanism which minimizes the pro-ductionofmucinsglycosaminoglycansandothercompounds capable of inhibiting calcium oxalate crys-tal growth has also been implicated in both cats anddogs.TheseinhibitorycompoundsincludeTammHorsfall protein, nephrocalcin and prothrombin frag-ments, which increase the solubility of calcium oxalateand prevent crystal aggregation.Calcium phosphate urolithsCalcium phosphate crystals form much less frequentlythaneitherstruviteorcalciumoxalateinbothcatsand dogs. Growth and aggregation can lead to stoneformationwhichhasbeenassociatedwithhyper-calcaemiaandhighurinecalciumconcentrations.Theyformmosteasilyinalkalineurine.Therearedifferent types of calcium phosphate uroliths, includ-inghydroxyapatite,carbonateapatiteandbrushite(tricalcium phosphate). They have been associatedwith increased dietary calcium, phosphorus and vita-minD;renaltubularacidosis;andhypercalcaemiaassociatedwithhyperparathyroidism,butnotpara-neoplasticsyndromes.TheycanformatanyurinepH. In dogs there is an increased incidence in malesbutnoageassociation.TheyaremorecommoninCockerSpaniels,YorkshireTerriersandMiniatureSchnauzers. They are uncommon in cats but occurmost frequently in middle-aged female cats, with nobreed predilection.Ammonium urate and uric acid urolithsTheseforminacidtoneutralpHurine.Theyareuncommon in both dogs and cats with the exception oftheDalmatian;inthisbreedthereisaninheritedreduced ability to oxidize uric acid to allantoin, causingaccumulation of uric acid in plasma and urine, whichcan lead to urolith formation. There is also an increasedincidence of these uroliths in other breeds, includingEnglish Bulldog, Yorkshire Terrier, Miniature Schnau-zer and Shih Tzu. These uroliths can also occur in dogsandcatswithseverehepaticdysfunctionandportosystemic shunts.Cystine urolithsTheseformduetoaninbornerrorofaminoacidmetabolism which leads to reduced tubular resorptionof cystine and consequent increased urinary cystineaccumulation. This results in cystine crystalluria and, insome cases, urolith formation. The condition is rare butis reported usually in young male dogs of the EnglishBulldog, Dachshund and Bassett Hound breeds. It israrely reported in cats.Silica urolithsThesearerarebuttheirformationinacidtoneutralurine,inassociationwithacidifyingdiets,hasbeenreported. Many of these diets contain large amounts ofplant gluten, soya bean and maize hulls which are highin silica. They have been found in middle-aged maledogs of the German Shepherd Dog, Golden Retrieverand Labrador Retriever breeds.Urinary tests for tubular damageUrine gamma-glutamyltransferase:creatinine ratioIfacutesevererenaltubulardamageornecrosisissuspected (e.g. following aminoglycoside treatment) aurinarytestfortubulardamagecanbeperformed.Gamma-glutamyl transferase (-glutamyl transpeptid-ase,GGT)issynthesizedbyrenaltubularepithelialcells, and when they are injured or sloughed, it is lostinto the urine in large amounts (although plasma GGTis not increased). Creatinine is not reabsorbed by thetubules, so urine GGT can be related to urine creatinineto correct for variation in urine SG. GGT and creatininearemeasuredbyautomaticmethodsinthesamesample of urine and a ratio obtained:Urine GGT (IU/l)Urine creatinine (mg/dl)UnitsmayneedtobeconvertedfromSIunitstoperform the calculation:Creatinine (mmol/l) x 1000/88.4 = Creatinine (mg/dl)A normal urine GGT:creatinine ratio of 0.14 0.10has been reported for adult dogs (Gossett et al., 1987),whilst a study of 6-month-old male Beagles reported ahigher value of 0.34 0.53 (Grauer et al., 1995). Theratio is increased with tubular damage, e.g. followinggentamycin-induced nephrotoxicosis.Assessment of polyuria/polydipsia bywater deprivation testingWater deprivation tests (WDT) are used in patients withhyposthenuria (i.e. SG 1.008,butnotto>1.025,becauseofADHantagonism.Whendesmopressin(DDAVP,asyn-thetic ADH analogue) is administered, concentratingability returns, thus mimicking CDI.If the animal is markedly polyuric, water deprivationshouldbedonewithextremecautionbecausesuchanimals may become rapidly dehydrated, as a resultof pre-existing medullary washout. In these animals itisbettertorestrictwaterintakepartiallyfor5daysbeforehand (120 ml/kg per day on days 5, 4 and 3,90 ml/kg on day 2 and 60 ml/kg on the day before thetest).Salt can be added to the food from day 5 to helpcorrect medullary washout.Tests used in conjunction with waterdeprivation testingEndogenous plasma ADH levels are used to distin-guish between CDI, NDI and PP in humans as partoftheWDT.ADHmeasurementisavailableonalimited basis for veterinary patients in human hospi-tallaboratoriesbutitisexpensiveandhasalongturnaround time, and, therefore, is impractical in mostclinic cases.TheHickeyHaretestissometimesusediftheWDTisnon-diagnostic.Thistestmeasuresrenaltubularandpituitaryresponsestohyperosmolality(intravenous hypertonic saline administration) by as-sessing the output, SG and, if possible, osmolality ofurine.InnormalanimalsandanimalswithPP,theurine output progressively decreases and urine SGandosmolalityincreasefollowinghypertonicsalineadministration, whilst there is no response in animalswith CDI and NDI. However there is a significant riskofinducingmarkedhypertonicity(hyperosmolality),especially in severely polyuric animals. The test re-quiresclosemonitoringandisprobablybestper-formed in referral hospitals.AcloselymonitoredtrialoftheADHanaloguedesmopressin (DDAVP) administration over 57 daysis often a safer alternative when WDT is non-diagnos-tic. Desmopressin administration should cause a >50%decrease in water intake in CDI, but will have no effectin NDI.Water deprivation test and its interpretation. 10.20ProtocolPartial water restriction for 23 days prior to the test is recommended,to correct medullary washout. About 100 ml/kg is allowed on the firstday, reducing by 1015% per day for 2 further days. On the fourth daycomplete water deprivation is commenced as follows:1. Empty bladder (catheter) measure urine S.G.2. Weigh animal3. Deprive the animal of food and waterAt 12 hourly intervals:1. Empty the bladder and measure urine S.G.2. Weigh the animal3. Measure serum/plasma urea and creatinine (optional)Discontinue the test when: The urine S.G. is >1.025 Or there has been >5% loss of body weight Or the animal becomes azotaemic or depressedInterpretationPP can be identified at this stage because the SG will become >1.025CDI and NDI will fail to concentrate above 1.010 even when there is>5% loss of body weightValues between 1.010 and 1.020 are equivocal and indicatesubmaximal concentration suggesting partial central DI.To distinguish between CDI and NDI the desmopressin responsetest is performed (preferably immediately after the WDT):1. Empty the bladder and measure urine SG2. Inject desmopressin intravenously or intramuscularly (2.0 gfor small dogs 15kg)3. Measure urine SG every 2 hours for 610 hours, then at 12and 24 hours4. Provide small amounts of water (3 ml/kg/hour) during andfollowing the test to prevent cerebral oedemaIntrepretation of desmopressin response test Urine SG values >1.015 indicative CDI Failure to concentrate above 1.010 is indicative of NDI Urine SG values between 1.010 and 1.015 are equivocal andcould reflect medullary washoutCase 1Signalment2-year-old entire female BoxerHistory2-monthhistoryofPD/PUwithasuddenonset.CystitishadbeenCase examplesdiagnosed and treated but the PD/PU persisted. The dog was drinking180280 ml of water/kg/day, but was otherwise bright and well. Therewere no abnormalities detected on clinical examination.Case 1 continues166Chapter 10 Urine analysisBiochemistry Result Reference intervalSodium (mmol/l) 149.6 136155Potassium (mmol/l) 4.07 3.55.8Chloride (mmol/l) 116 107120Glucose (mmol/l) 5.6 3.45.3Urea (mmol/l) 4.5 3.38.0Creatinine (mol/l) 103 45150Calcium (mmol/l) 2.73 2.22.9Inorganic phosphate 1.46 0.82.0(mmol/l)TP (g/l) 62.3 6080Albumin (g/l) 31.5 2545Globulin (g/l) 30.8 2141ALT (IU/l) 17 2159ALP (IU/l) 83 3142Bile acids (mol/l) 2 5% oforiginal body weight and increasing plasma osmolality). This excludespsychogenicpolydipsiaandisconsistentwithnephrogenicorcentraldiabetesinsipidus(CDI).UrinebecamemoreconcentratedfollowingadministrationofDDAVP,indicatingCDI.Intheabsenceofotherneurological signs or history of trauma, the CDI was considered idio-pathic, although underlying causes such as neoplasia were not investi-gated further.Case outcomeThe clinical signs were well controlled with DDAVP drops administeredinto the conjunctival sac. The dog was lost to follow-up after 6 months.(Case 1 courtesy of E Villiers.)Clinical pathology dataCase 1 continuedCase 2Signalment13-year-old female Bearded Collie.History and clinical findings5-month history of haematuria. Increased frequency of urination;dysuria and nocturia. Multiple courses of antibiotics. Possible discomforton sitting down. Very tense on abdominal palpation. No other significantclinical findings.Case 2 continues167Chapter 10 Urine analysisClinical pathology dataUrine analysisSG (refractometer) 1.024Dipstick results pH 6.5; protein + to ++; blood +++;negative for glucose, ketones,urobilinogen, bilirubin,haemoglobinSediment examination See Figure 10.21What abnormalities are present?Urinalysis Mild to moderate proteinuria Marked haematuria: this may account for the proteinuria as the doghas gross haematuria SG in keeping with polyuria, or early renal failure.Urine cytology Mixedpopulationofcells,consistingofneutrophilsandepithelialcells Neutrophils are degenerate and show karyolysis. Intracellular bacte-ria are seen. Both rods (likely to be Escherichia coli in this site) andcocci are present Epithelial cells are pleomorphic, with some very large cells with highnuclear:cytoplasmic ratio and open chromatin. Binucleate cells arealso seen. Cytoplasm is variably basophilic but in some cells showsincreased basophilia, and vacuolation is also apparent Numerous background RBCs and free bacteria.How would you interpret these results andwhat are the likely differential diagnoses?The cytological findings confirm that the dog has bacterial cysititis. Thetransitional epithelial cells show features suggestive of malignancy but,in the presence of a florid inflammatory response (and with the very longhistory of urinary tract disease), these changes must be interpreted withcaution, as dysplastic cells may mimic neoplasia.What further tests would you recommend? Culture and sensitivity testing Imaging to identify any mass lesion, and suction biopsy via catheterif indicated, or cystoscopy and biopsy.Results of further testsA pneumocystogram and double-contrast cystogram (Figures 10.22 and10.23) showed an ill-defined mass extending from the apex of the bladderalong the dorsal wall almost to the trigone. The outline is irregular, witha moth-eaten appearance suggesting mucosal disruption. The bladderwall appears thickened craniodorsally: on the pneumocystogram, thismay be a result of insufficient inflation, but on the double-contrast studythis is a genuine finding. This extensive ill-defined irregular mass, whichhas caused mucosal disruption, is most likely neoplastic, and most likelya transitional cell carcinoma. This should be confirmed by suction biopsy(declined by the owner on grounds of cost).These findings are consistent with a bladder tumour with secondaryurinary tract infection. Great care should be taken in diagnosing neopla-sia on urine cytology, especially if there is concurrent inflammation, as inthis case. The atypical cellular features could have been due to tissuedysplasia,causedbythesevereinflammationpresent;andfurtherdiagnostic investigations should always be performed when neoplasia issuspected cytologically.Case outcomeThe dog was treated palliatively with piroxicam, and survived for a further6 months.(Case 2 courtesy of L Blackwood.)Case 2 continuedReferences and further readingGossett KA, Turnwald GH, Kearney MT et al. (1987). Evaluation ofgamma-glutamyl transpetidase - to - creatinine ratio from spoturine samples of urine supernatant as an indicator of urinaryyenzymeexcretionindogs.AmericanJournalofVeterinaryResearch 48, 455457GrauerGF,GrecoDS,BehrendENetal.(1995)Estimationofquantitativeenzymuriaindogswithgentamycin-inducednephrotoxicosis using enzyme/creatinine ratios from spot urinesamples. Journal of Veterinary Internal Medicine 9, 323327Grauer GF, Oberhauser EB, Basaraba RJ, Lappin MR, Simpson DFandJensenDF(2002).Developmentofmicroalbuminuriaindogswithheartwormdisease.JournalofVeterinaryInternalMedicine 16, 352 (abstract)Pneumocystogram. 10.22Double contrast cystogram. 10.23Cytological appearance of the urine sediment, showing variousareas of the smear. (Wrights stain; original magnification X1000.)10.21168Chapter 10 Urine analysisHeuter KJ, Buffington CA and Chew DJ (1998) Agreement betweentwo methods for measuring urine pH in cats and dogs. Journal ofthe American Veterinary Medical Association 213, 996998HoustonDM,MooreAE,FavrinMGandHofB(2004)Canineurolithiasis:alookatover16,000urolithsubmissionstotheCanadian Veterinary Urolith Centre from February 1998 to April2003. Canadian Veterinary Journal 45, 225230Houston DM, Moore AE, Favrin MG and Hoff B (2003) Feline urethralplugs and bladder uroliths: a review of 5,484 submissions 19982003. Canadian Veterinary Journal 44, 974977Jensen WA, Grauer GF, Andrews J and Simpson DF (2001) Prevalenceofmicroalbuminuriaindogs.JournalofVeterinaryInternalMedicine 15, 300 (abstract)Latimer KS, Mahaffey EA and Prasse KW (2003) Urinary System. In:DuncanandPrassesVeterinaryLaboratoryMedicineClinicalPathology,4thedn,ed.CRGregory,pp.231259.IowaStatePress, IowaLing GV, Thurmond MC, Choi YK, Franti CE, Ruby AL, Johnson DL(2003) Changes in proportion of canine urinary calculi composedof calcium oxalate or struvite in specimens analyzed from 1981through 2001. Journal of Veterinary Internal Medicine 17, 817823Osborne CA and Stevens JB (1999) Handbook of Canine and FelineUrinalysis. Bayer Scientific, Leverkusen, GermanyPresslerBM,ProulxDA,WilliamsLE,JensenWAandVadenSL(2003)Urinealbuminconcentrationisincreasedindogswithlymphomaorosteosarcoma.JournalofVeterinaryInternalMedicine 17, 404 (abstract)Radecki S, Donnelly R, Jensen WA and Stinchcomb DT ( 2003) Effectof age and breed on the prevalence of microalbuminuria in dogs.Journal of Veterinary Internal Medicine 17, 406 (abstract)RaskinRE,MurrayKAandLevyJK(2002)Comparisonofhomemonitoring methods for feline urine pH measurement. VeterinaryClinical Pathology 31, 5155VadenSL,JensenWAandSimpsonD(2001)Prevalenceofmicroalbuminuria in dogs evaluated at a referral veterinary hospital.Journal of Veterinary Internal Medicine 15, 300 (abstract)Vaden S L, Barrak M P, Lappin M R and Jensen W A (2004) Effectsof urinary tract inflammation and sample blood contamination onurinealbuminandtotalproteinconcentrationsincanineurinesamples. Veterinary Clinical Pathology 33, 1419Wisnewski N, Clarke KB, Powell TD and Sellins KS (2004) Prevalenceof microalbuminuria in cats. www.heska.com/erd/erd_datacat.asp