Relationships Between Degree of Azotaemia and Blood Pressure,Urinary Protein:Creatinine Ratio and Fractional Excretion of Electrolytes in Dogs with Renal Azotaemia

Blood pressure (BP) was measured in 31 renal azotaemic dogs by oscillometric measurement at the posterior tibia artery, and urine and blood samples were collected. Haematology, blood chemistry and urinalysis were performed and urinary protein:creatinine ratio (UPC) and fractional excretions of electrolytes (FE_e) were calculated. The results showed that only 19% of dogs with renal azotaemia were hypertensive, whereas almost all of them had high urinary protein and electrolyte excretions. There was no association between BP, UPC and FE_e. A positive correlation was found between all pairs of electrolyte fractional excretions. When the severity of renal impairment was observed using plasma creatinine concentration, neither BP nor UPC was correlated. Only the FE _e was associated with the degree of azotaemia. The results suggest that dogs with renal azotaemia do not necessarily have hypertension. The fractional urinary excretion of electrolytes may be a good indicator for severity of renal dysfunction in azotaemic dogs.     

Effects of urinary tract inflammation and sample blood contamination on urine albumin and total protein concentrations in canine urine samples

BACKGROUND: Urinary tract inflammation and hemorrhage are believed to be common causes of proteinuria in dogs based on results of studies that measured total urine protein concentration. A method to quantify urine albumin (UAlb) concentration in dogs recently has become available; however, the effect of inflammation on albuminuria is unknown. OBJECTIVES: The goals of this study were to determine the effects of urinary tract inflammation, as indicated by pyuria and sample blood contamination, on UAlb concentration and on urine protein:creatinine (UPC) ratio in dogs. METHODS: Urine samples were obtained from dogs with pyuria that were presented to a veterinary teaching hospital or were part of a laboratory colony. To mimic the effects of hematuria, canine whole blood was added to a microscopically normal canine urine sample that had baseline albumin and total protein concentrations below the limits of detection. UAlb concentration was measured using a canine albumin-specific competitive ELISA. UPC ratio was determined using routine methods. RESULTS: Of 70 samples with pyuria, 67% had negligible UAlb concentrations and 81% had normal UPC ratios. UAlb concentration but not UPC ratio was significantly higher (P < 0.05) in samples with concurrent hematuria or bacteriuria. When whole blood was added to normal urine, UAlb concentration did not exceed 1 mg/dL until the sample became visibly pink; the UPC did not exceed 0.4 at any dilution. CONCLUSIONS: Many dogs with pyuria do not have albuminuria or proteinuria; however, albuminuria may be more likely in dogs with pyuria and concurrent hematuria or bacteriuria. Hematuria may not cause an increase in UAlb concentration until it becomes macroscopic and even then may not increase the UPC ratio.     

Day-to-Day variation of the urine protein: creatinine ratio in female dogs with stable glomerular proteinuria caused by X-linked hereditary nephropathy

BACKGROUND: Interpretation of serial urine protein:creatinine (UPC) values is confounded by a lack of data regarding random biologic variation of UPC values in dogs with stable glomerular proteinuria. HYPOTHESIS: That there is minimal day-to-day variability in the UPC of dogs with unchanging proteinuria and the number of measurements needed to reliably estimate UPC varies with the magnitude of proteinuria. ANIMALS: Forty-eight heterozygous (carrier) female dogs with X-linked hereditary nephropathy (XLHN) causing stable proteinuria. METHODS: Urine samples were obtained daily by cystocentesis for 3 consecutive days on 183 occasions (549 samples). The UPC was measured for each sample with a single dry-film chemistry auto-analyzer. Data were analyzed retrospectively by a power of the mean model because the variance of UPC values within the 3-day evaluation periods increased as the magnitude of proteinuria increased. RESULTS: To demonstrate a significant difference (P < .05) between serial values in these proteinuric dogs, the UPC must change by at least 35% at high UPC values (near 12) and 80% at low UPC values (near 0.5). One measurement is adequate to reliably estimate the UPC when UPC <4, but 2-5 determinations are necessary at higher UPC values. CONCLUSIONS AND CLINICAL IMPORTANCE: These guidelines for interpretation of serial UPC values in female dogs with XLHN may also be helpful for interpretation of UPC values in dogs with other glomerulopathies.     

Diet modulates proteinuria in heterozygous female dogs with X-linked hereditary nephropathy

Young adult heterozygous (carrier) female dogs with X-linked hereditary nephropathy (XLHN) have glomerular proteinuria but are otherwise healthy. Because data regarding dietary influences on the magnitude of proteinuria in dogs with spontaneous glomerular disease are not available, 12 such dogs were studied in a double crossover experiment intended to determine effects of altering dietary protein intake for up to 6 weeks. Dogs were blocked by urine protein : creatinine ratio (UPC) and randomly assigned to receive 2 diets: high protein (34.6% dry matter [DM], HP) or low protein (14.1% DM, LP) fed in HP-LP-HP or LP-HP-LP sequence. Food intake was measured daily, body weight (BW) was measured twice weekly, and UPC, plasma creatinine, blood urea nitrogen, phosphorus, albumin, and protein concentrations were measured at 2-week intervals. Nutrient digestibility was measured during the third treatment period. Diet had a significant effect (P < .0001) on all measured variables except plasma phosphorus (P > .5), but unintended differences in digestibility of protein and energy (P < or = .01) prevented assignment of the diet effect exclusively to protein. Proteinuria was greater (UPC 4.7 +/- 2.2 versus 1.8 +/- 1.1, P < .0001) when the HP diet was fed, but the LP diet did not maintain starting BW or plasma albumin concentration within the normal reference range. Diet greatly affects the magnitude of proteinuria in XLHN carrier females. Dietary protein restriction can reduce proteinuria in dogs with glomerular disease, but BW and blood protein concentrations may not be maintained if the restriction is too severe.     

Serum ferritin and paraoxonase-1 in canine leishmaniosis

Ferritin and paraoxonase-1 (PON-1) were measured in dogs experimentally infected by Leishmania infantum (during experimental infection and following treatment) and also in naturally-infected dogs which presented different degrees of proteinuria. Experimentally-infected dogs were monitored for 7 months post-infection, then treated for 3 months with allopurinol, and their response to therapy was followed for 11 additional months. Naturally-infected dogs were staged based on the urine protein/creatinine (UPC) ratio into three groups as follows: group 1 (non-proteinuric; UPC ratio: <0.2), group 2 (borderline proteinuric; UPC ratio: 0.2–0.5) and group 3 (proteinuric; UPC ratio >0.5). An increase in serum ferritin values and a decrease in PON-1 activity were observed 2 months after infection. Both analytes returned to preinfection values following treatment. Significantly higher concentrations of ferritin were observed in dogs classified as either borderline or proteinuric when compared with non-proteinuric dogs whereas serum PON-1 activity was decreased only in proteinuric dogs.     

Associations between proteinuria, systemic hypertension and glomerular filtration rate in dogs with renal and non-renal diseases

Proteinuria and systemic hypertension are well recognised risk factors in chronic renal failure (CRF). They are consequences of renal disease but also lead to a further loss of functional kidney tissue. The objectives of this study were to investigate the associations between proteinuria, systemic hypertension and glomerular filtration rate (GFR) in dogs with naturally occurring renal and non-renal diseases, and to determine whether proteinuria and hypertension were associated with shorter survival times in dogs with CRF. Measurements of exogenous creatinine plasma clearance (ECPC), urine protein:creatinine ratio (UPC), and Doppler sonographic measurements of systolic blood pressure (SBP) were made in 60 dogs with various diseases. There was a weak but significant inverse correlation between UPC and ECPC, a significant inverse correlation between SBP and ECPC and a weak but significant positive correlation between UPC and SBP. Some of the dogs with CRF were proteinuric and almost all were hypertensive. Neoplasia was commonly associated with proteinuria in the dogs with a normal ECPC. CRF was the most common cause leading to hypertension. In the dogs with CRF, hypertension and marked proteinuria were associated with significantly shorter survival times.     

Evaluation of kidney injury in dogs with pyometra based on proteinuria, renal histomorphology, and urinary biomarkers

Background: Proteinuria is a feature of pyometra‐associated renal dysfunction, but its prevalence and clinical relevance are not well characterized. Objectives: To define which subset of dogs with pyometra has clinically relevant kidney injury by quantification of proteinuria; light, immunofluorescence, and electron microscopic examination of kidney biopsy specimens; and measurement of urinary biomarkers. Animals: Forty‐seven dogs with pyometra. Ten clinically healthy intact bitches of comparable age. Methods: Prospective study. Routine clinicopathological variables including urinary protein to creatinine ratio (UPC) were analyzed. Validated assays were used to quantify urinary biomarkers for glomerular (urinary albumin, urinary immunoglobulin G, urinary C‐reactive protein, urinary thromboxane B₂) and tubular function (urinary retinol‐binding protein, urinary N‐acetyl‐β‐d ‐glucosaminidase). Kidney biopsy specimens from 10 dogs with pyometra and dipstick urine protein concentrations of 2+ or 3+ were collected during ovariohysterectomy. Urinalysis was repeated within 3 weeks after surgery in 9 of the 10 dogs. Results: UPC (median, range) was significantly higher in dogs with pyometra (0.48, 0.05–8.69) compared with healthy bitches (0.08, 0.02–0.16) (P < .01). Twenty‐two of 47 dogs with pyometra had UPC>0.5, 12 had UPC>1.0, and 7 had UPC>2.0. Glomerulosclerosis and tubulointerstitial nephritis were common kidney biopsy findings in proteinuric dogs with pyometra. Dogs with glomerulosclerosis (5/10), either global or focal and segmental, had UPC>1.0 at ovariohysterectomy and afterward. Dogs with structural glomerular and tubular changes mostly had urinary biomarker to creatinine ratios above the 75th percentile. Conclusion: Dogs with pyometra and UPC>1.0 or high ratios of urinary biomarkers appear likely to have clinically relevant renal histologic lesions and require monitoring after ovariohysterectomy. Future studies should evaluate the role of pyometra‐associated pathogenic mechanisms in causing or exacerbating focal and segmental glomerulosclerosis in dogs.     

Use of urine albumin/creatinine ratio for estimation of proteinuria in cats and dogs

The clinical utility of the urine albumin/creatinine ratio (UAC) using a simplified analyzer for estimation of proteinuria was studied in cats and dogs. Measurement results for diluted feline and canine albumin standard solutions showed linearity. Although conversion formulas (y=1.28x+1.04 and y=1.67x+10.47 for cats and dogs, respectively) were necessary, urine albumin concentrations could be determined in both animals. In cats and dogs with proteinuria, the UAC changed parallel with the urine protein/ creatinine ratio (UPC), and the Log UAC and Log UPC were significantly correlated (r=0.803 (p<0.01) in cats, r=0.801 (p<0.01) in dogs). The UAC using an UAC analyzer could be used clinically as one of the basic in-hospital laboratory tests for estimation of proteinuria in cats and dogs.     

Use of protein-to-creatinine ratio in a single urine specimen for quantitative estimation of canine proteinuria

The daily excretion of urinary protein was evaluated in 8 conditioned research dogs and in 10 hospitalized, proteinuric dogs, using 24-hour urine collections. Concurrent with each 24-hour urine collection, a 5- to 10-ml urine specimen was obtained during midday. The ratio of urine protein to urine creatinine concentration was determined from the single urine specimen for each dog. Linear regression analysis was used to calculate the correlation between that ratio and the 24-hour urinary protein loss (mg/kg of body weight). The coefficient of determination was significant (r2 = 0.95, P less than 0.0001). Determination of the protein-to-creatinine ratio in a single urine specimen was found to be a sensitive, rapid, and dependable diagnostic technique for detection and quantitative estimation of proteinuria.     

Estimation of Quantitative Enzymuria in Dogs With Gentamicin-Induced Nephrotoxicosis Using Urine Enzyme/Creatinine Ratios From Spot Urine Samples

The correlation between 24-hour urinary excretion of N -acetyl-β- d -glucosaminidase (NAG) and γ-glutamyl transferase (GGT) with urine NAG and GGT/creatinine ratios was assessed in dogs with gentamicin-induced nephrotoxicosis. Eighteen 6-month-oid male Beagles with normal renal function were randomly divided into 3 groups of 6. Each group was fed a different concentration of protein (high protein, 27.3%; medium protein, 13.7%; and low protein, 9.4%) for 21 days. After dietary conditioning, gentamicin was administered at a dose of 10 mg/kg IM tid for 8 days and each group was continued on its respective diet. Endogenous creatinine clearance and 24-hour urinary excretion of NAG and GGT were determined after dietary conditioning (day 0) and on days 2, 4, 6, and 8 of gentamicin administration. In addition, urine NAG and GGT/creatinine ratios (IU/L ± mg/dL) were determined from catheterized spot urine samples obtained between 7 and 10 am on the same days. The correlation between 24-hour urinary enzyme excretion and urine enzyme/creatinine ratio in the spot urine samples was evaluated by simple linear regression analysis. Spot sample urine enzyme/creatinine ratios were significantly correlated with 24-hour urinary enzyme excretion through day 4 for dogs on low dietary protein, through day 6 for those on medium protein, and through day 8 for those on high dietary protein. Mean ± SD baseline values for urine NAG/creatinine ratio and 24-hour urinary NAG excretion were 0.06 ± 0.04 and 0.19 ± 0.14 IU/kg/24 hr, respectively. Baseline values for urine GGT/creatinine ratio and 24-hour urinary GGT excretion were 0.39 ± 0.18 and 1.42 ± 0.82 IU/kg/24 hr, respectively.     

Comparison of a semiquantitative point-of-care assay for the detection of canine microalbuminuria with routine semiquantitative methods for proteinuria

Background: It has been speculated that renal disease can be identified through the detection and quantification of microalbuminuria, however, reliable measurement of albuminuria in any quantity can be challenging. Recently, a new point‐of‐care immunoassay was validated for the specific detection of microalbuminuria and early renal disease in dogs. Objectives: The goal of this study was to determine if measurement of microalbuminuria by the point‐of‐care immunoassay correlated with results from routine semiquantitative methods for detecting proteinuria in dogs. Methods: One hundred and thirty‐eight urine samples, from 133 different dogs, submitted for urinalysis to the Clinical Pathology Laboratory at the University of Missouri‐Columbia Veterinary Medical Teaching Hospital were eligible for the study. Samples that contained >20 RBC/high power field (hpf) or >20 WBC/hpf were excluded, as were samples with insufficient volume to complete all tests. All samples were evaluated with a urinary dipstick with or without a sulfosalicylic acid turbidimetric test, a urine protein:creatinine (UPC) ratio, and the immunoassay for microalbuminuria. Data were analyzed by the Spearman rank order correlation. Results: Microalbuminuria results correlated significantly with those of the dipstick (r= 0.715), sulfosalicylic acid test (r= 0.742), and UPC ratio (r= 0.830). Correlation between the immunoassay and UPC ratio was the same (r= 0.830) when only samples with trace or 1+ proteinuria by dipstick were analyzed (n = 51). Conclusions: The point‐of‐care immunoassay results for microalbuminuria correlated with the results of semiquantitative methods for detecting total proteinuria in dogs. Routine methods for canine proteinuria appear to be adequate for determining whether further testing for renal disease is warranted.     

Glomerular filtration rate in dogs with leishmaniasis and chronic kidney disease

BACKGROUND: Glomerular filtration rate (GFR) measurement is an indicator of kidney function. However, its usefulness in dogs at early stages of spontaneous chronic kidney disease (CKD) of glomerular origin, where routine laboratory techniques are not sufficiently sensitive, remains unproved. HYPOTHESIS: That GFR is reduced in proteinuric nonazotemic or mildly azotemic dogs with CKD secondary to leishmaniasis. ANIMALS: Twenty-six dogs with CKD secondary to leishmaniasis and 10 healthy dogs (control group). METHODS: CBC, serum biochemistry, and urinalysis (microalbuminuria and urine protein/creatinine ratio [UPC]) were performed in all dogs. GFR was calculated by measuring exogenous creatinine clearance. Based on degree of proteinuria and serum creatinine concentration (SCr), dogs were classified as group A (control; n = 10): UPC < 0.2, SCr < 1.4 mg/dL; group B (n = 8): UPC, 0.2-0.5, SCr < 1.4 mg/dL; group C (n = 10): UPC > 0.5, SCr < 1.4 mg/dL; group D (n = 5): SCr, 1.4-2 mg/dL; group E (n = 3): SCr > 2 mg/dL. Results: GFR (mL/kg/min) was 3.9 +/- 0.29, 4.4 +/- 0.74, 4.5 +/- 1.44, 2.8 +/- 0.97, and 1.5 +/- 0.43 for groups A, B, C, D, and E, respectively. Eleven dogs (1 from group B, 3 from group C, 4 from group D, and all 3 dogs from group E) had an abnormally low GFR. Four dogs from group B and 5 dogs from group C had a GFR above the upper reference range (>4.5 mL/min/kg). CONCLUSION AND CLINICAL RELEVANCE: Some proteinuric nonazotemic or mildly azotemic dogs with leishmaniasis have low GFR, but glomerular hyperfiltration occurs in other dogs.     

The use of pooled vs serial urine samples to measure urine protein:creatinine ratios

Background: Evaluation of serial urine protein:creatinine (UPC) ratios is important in prognosticating chronic kidney disease and monitoring response to therapeutic interventions. Owing to random biologic variation in dogs with stable glomerular proteinuria, multiple determinations of UPC ratios often are recommended to reliably assess urine protein loss. This can be cost‐prohibitive. Objective: The purpose of this study was to evaluate agreement between the mean of 3 UPC ratios obtained on 3 separate urine samples per dog and a single UPC ratio obtained when aliquots of the separate samples were pooled and analyzed as 1 sample. Methods: Three separate urine samples were collected from each of 25 dogs, both client‐owned and members of a research colony. Protein and creatinine concentrations were measured in the supernatant of each sample using a biochemical analyzer, and the mean of the 3 UPC ratios was calculated. A 1.0 mL aliquot of each of the 3 samples from each dog was pooled to create a fourth sample for that dog, and the UPC ratio of the pooled sample was similarly determined. Agreement and correlation between the mean and pooled UPC ratios were assessed using Bland–Altman difference plots and regression analysis, respectively. Results: The UPC ratio in the pooled samples was highly correlated (r=.9998, P<.0001) with the mean UPC ratio of the 3 separate samples. Strong agreement between results was demonstrated; a UPC ratio from a pooled sample was at most ±20% different than the mean UPC ratio obtained from 3 separate samples. Conclusions: Measuring the UPC ratio in a pooled sample containing equal volumes of several different urine specimens from the same dog provides a reliable and cost‐effective alternative to assessing multiple UPC ratios on several specimens from the same dog.     

Absence of urinary tract infection in dogs with experimentally induced hyperadrenocorticism

Objectives of this study were to determine occurrence of urinary tract infection and describe results of urine analysis and urine culture in dogs with experimentally induced hyperadrenocorticism. Dogs were randomly assigned to receive either hydrocortisone (nine dogs) or placebo (eight dogs) for 49 consecutive days. Before and on day 49 of treatment, evaluation of dogs included physical examination, abdominal ultrasound, urine culture, urinalysis, adrenal function testing, and measurement of urine protein and creatinine and activity of serum alkaline phosphatase. All dogs in the experimental group had clinical and laboratory findings of hyperadrenocorticism. Urine specific gravity was significantly decreased and urine protein-to-creatinine ratio was significantly increased in dogs with hyperadrenocorticism. Urinary tract infection did not occur in any dogs. We conclude that administration of hydrocortisone created a model of hyperadrenocorticism; however, urinary tract infection did not occur. Additional evaluation is needed to determine association between urinary tract infection and hyperadrenocorticism.     

Prevalence of proteinuria in a canine oncology population

Objective

To evaluate the point prevalence of proteinuria in dogs presenting to the University of Georgia Oncology Service for the first time.

Materials and Methods

In this prospective study, 60 client‐owned dogs with a confirmed cancer diagnosis were included but those with lower urinary tract neoplasia were excluded. Each dog's signalment, cancer diagnosis, previous cancer treatments, current medications and travel history were recorded. Renal values, electrolytes, packed cell volume, total solids, systolic blood pressure, urinalysis, urine protein:urine creatinine and retinal examinations were recorded. Non‐proteinuric, borderline proteinuria and overt proteinuria were defined as urine protein:urine creatinine <0·2, ≥0·2 but <0·5, and ≥0·5, respectively. Urine culture was performed in dogs with active urine sediments or overt proteinuria.

Results

Twenty‐nine dogs were non‐proteinuric (48·3%), 22 (36·7%) borderline proteinuric and nine (15%) overtly proteinuric. None were azotaemic. Hypertension (systolic blood pressure ≥160 mmHg) was detected in 18 (30%) dogs. Of these, six were non‐proteinuric, nine borderline proteinuric, and three overtly proteinuric. Proteinuria was detected in 51% of dogs presented to our oncology service, the majority of which were classified as borderline.

Clinical Significance

The high proportion of proteinuria in dogs in this study suggests that screening for proteinuria in dogs with cancer may be prudent. Larger studies are required to correlate specific cancer types and the impact of treatment with the development, magnitude and persistence of proteinuria.     

Does blood contamination of urine compromise interpretation of the urine protein to creatinine ratio in dogs?

AIMS: To determine the effect of contamination of urine with 0–5% blood, varying in haematocrit and protein concentrations, on the urine protein to creatinine ratio (UPC) in dogs, and to determine whether the colour of urine can be used to aid interpretation of UPC results.

METHODS: Urine samples were collected by free catch from 18 dogs, all of which had UPC?<0.2. Venous blood samples were also collected from each dog, and the blood from each dog was added to its own urine to produce serial concentrations of 0.125–5% blood. The colour of each urine sample was recorded by two observers scoring them as either yellow, peach, orange, orange/red or red. Protein and creatinine concentrations were determined, and dipstick analysis and sediment examination was carried out on each sample. Based on colour and dipstick analysis, samples were categorised as either having microscopic, macroscopic or gross haematuria. A linear mixed model was used to examine the effect of blood contamination on UPC.

RESULTS: The uncontaminated urine of all 18 dogs had a UPC?<0.2. Adding blood to the urine samples resulted in an increase in UPC at all contamination concentrations compared to the non-contaminated urine (p<0.001). None of the 54 samples with microscopic haematuria had UPC?>0.5. For 108 samples with macroscopic haematuria the UPC was >0.5 in 21 samples (19.4 (95% CI=13.1–27.9)%), and for 54 samples with gross haematuria 39 (72 (CI=59.1–82.4)%) had a UPC?>0.5. No samples had a UPC?>2.0 unless the blood contamination was 5% and only 3/18 (17%) samples at this blood contamination concentration had a UPC?>2.0.

CONCLUSIONS AND CLINICAL RELEVANCE: This study showed that while blood contamination of ≥0.125% does increase the UPC, if the urine remains yellow (microscopic haematuria), then there is negligible chance that a UPC?>0.5 will be solely due to the added blood. In that scenario, attributing the proteinuria present to the haematuria in the sample would be inappropriate. However blood contamination that results in discolouration of the urine sample from yellow (indicating macroscopic or gross haematuria) could increase the UPC above the abnormal range and would need to be considered as a differential for the proteinuria. Thus knowledge of urine colour, even if limited to simple colour scores (yellow, discoloured, red) could be utilised to aid interpretation of the UPC in samples with haematuria.     

Urinary catecholamine and metanephrine to creatinine ratios in healthy dogs at home and in a hospital environment and in 2 dogs with pheochromocytoma

BACKGROUND: Measurement of high concentrations of urine catecholamines and metanephrines is useful in diagnosing pheochromocytoma in humans. Stress increases catecholamine excretion in urine. HYPOTHESIS: Stress of a hospital visit increases urinary catecholamine and metanephrine excretion in dogs. ANIMALS: Fourteen clinically normal dogs, 2 dogs with pheochromocytoma. METHODS: Voided urine samples were collected by the owners 7 days before (t-7), during the hospital visit immediately after diagnostic procedures (t0), as well as 1 (t1) and 7 days (t7) after the hospital visit. Urine catecholamine and metanephrine concentrations were measured using high-pressure liquid chromatography and expressed as ratios to urine creatinine concentration. RESULTS: In client-owned dogs epinephrine and norepinephrine ratios at t0 were significantly higher compared with ratios at t7. Metanephrine and normetanephrine ratios at t-7, t0, and t1 did not differ significantly from each other; however, at t7 they were significantly lower compared to values at t-7. In staff-owned dogs no significant differences were detected among the different collecting time points for any variable. Metanephrine and normetanephrine ratios were significantly higher in client-owned dogs compared to staff-owned dogs at t-7, t0, and t1 but not at t7. CONCLUSIONS AND CLINICAL IMPORTANCE: Stress associated with a hospital visit and with the sampling procedure causes increases in urine catecholamine and metanephrine excretion. Urine collection for the diagnosis of pheochromocytoma probably should take place at home after adaptation to the sampling procedure.     

Comparison of Single,Averaged, and Pooled Urine Protein:Creatinine Ratios in Proteinuric Dogs Undergoing Medical Treatment

Background

Monitoring urine protein:creatinine ratios (UPC ) in dogs with protein‐losing nephropathy (PLN ) is challenging because of day‐to‐day variation in UPC results.

Hypothesis/Objectives

Determine whether single, averaged, or pooled samples from PLN dogs receiving medical treatment yield comparable UPC s, regardless of degree of proteinuria.

Animals

Twenty‐five client‐owned PLN dogs receiving medical treatment.

Methods

UPC ratios were prospectively measured in each dog utilizing 3 methods: single in‐hospital sample (day 3), average sample (days 1–3), and pooled sample (equal pooling of urine from days 1–3). Bland‐Altman analysis was performed to evaluate agreement between methods for all dogs, as well as in subgroups of dogs (UPC ≤4 or UPC >4).

Results

For all dogs, Bland‐Altman log‐transformed 95% limits of agreement were ?0.07–0.18 (single versus pooled UPC ), ?0.06–0.16 (single versus average UPC ), and ?0.06–0.04 (pooled versus average UPC ). For dogs with UPC ≤4, Bland‐Altman 95% limits of agreement were ?0.42–0.82 (single versus pooled UPC ), ?0.38–0.76 (single versus average UPC ), and ?0.27–0.25 (pooled versus average UPC ). For dogs with UPC >4, Bland‐Altman 95% limits of agreement were ?0.17–2.4 (single versus pooled UPC ), ?0.40–2.2 (single versus average UPC ), and ?0.85–0.43 (pooled versus average UPC ).

Conclusions and Clinical Importance

UPC ratios from all methods were comparable in PLN dogs receiving medical treatment. In PLN dogs with UPC >4, more variability between methods exists likely because of higher in‐hospital results, but whether this finding is clinically relevant is unknown.

     

Estimation of 24-h aldosterone secretion in the dog using the urine aldosterone:Creatinine ratio

ObjectivesOne potential method of evaluating renin–angiotensin–aldosterone system (RAAS) activation involves the quantification of urinary aldosterone excretion. While blood concentrations of aldosterone are easily obtained, results may be misleading because of minute-to-minute variation in aldosterone secretion and subsequent blood concentrations. Urinary aldosterone concentration measurement represents a more consistent “pooled” index of aldosterone secretion, but obtaining 24-h urine samples is time-consuming, difficult, and fraught with potential error. We postulated that the urinary aldosterone:creatinine ratio, measured from spot urine samples, would correlate well with 24-h urinary aldosterone excretion, and would provide a simple index of aldosterone excretion that would eliminate the need for 24-h urine collection.Animals, materials and methodsAfter validating an assay for aldosterone in canine urine, 24-h urinary aldosterone excretion was determined by radioimmunoassay from 8 normal, male beagle dogs under control conditions, after RAAS stimulation with amlodipine administration, and after RAAS attenuation with the addition of enalapril to amlodipine administration. Spot urine samples, each obtained at the same time of day, were used to determine the aldosterone:creatinine ratio during control conditions, RAAS stimulation, and RAAS attenuation.ResultsThe aldosterone:creatinine ratio from spot-checked urine samples correlated well with 24-h urinary aldosterone excretion (r = 0.77, P < 0.0001).ConclusionsA spot urinary aldosterone:creatinine ratio might be substituted for 24-h urinary aldosterone determination.     

Evaluation of a commercial in-house test kit for the semi-quantitative assessment of microalbuminuria in cats

Proteinuria was assessed in 100 randomly selected sick cats and 22 healthy cats by means of the urine protein:creatinine ratio, a traditional urine "dipstick" and a commercial ELISA-based dipstick designed to detect microalbuminuria (MA) semi-quantitatively. In addition the repeatability and reproducibility of the MA test was assessed by comparing results of five replicate tests of 26 urine samples, interpreted by two different readers. Discrepancies existed in the replicate test result in 23 and 27% of the samples examined by reader 1 and 2, respectively, and on several occasions this discrepancy was between whether the sample was "positive" or "negative" for MA. The inter-reader agreement was good (kappa=0.75), but again discrepancies were noted and part of the reason for these problems appeared to be the necessary subjectivity in the interpretation of colour changes when reading test results. Proteinuria was significantly (P< or =0.014) more prevalent in the sick than the healthy cats with 36 and 9%, respectively, having detectable MA, 34 and 5%, respectively, having a urine protein to creatinine (UPC) ratio >0.5, and 84 and 9%, respectively, having positive urine protein dipstick analysis. There was a moderate significant correlation between UPC ratio and MA concentrations (r(s)=0.68, P<0.0001). While 13/87 cats with a UPC ratio < or =0.5 had positive MA results, 10/84 cats with negative MA results had a UPC ratio >0.5, and none of these had evidence of lower urinary tract disease. This study confirmed that MA and proteinuria are commonly seen in cats with a variety of diseases, but they are not necessarily both elevated, and the UPC ratio can be elevated without an increase in MA results. Furthermore, some repeatability problems were demonstrated with the semi-quantitative MA test. These findings demonstrate that the semi-quantitative MA test should not be relied on as the sole determinant of proteinuria.