Relationships among urinary protein-to-creatinine ratio, urine specific gravity, and bacteriuria in canine urine samples

Urine Neutrophil Gelatinase-Associated Lipocalin in Non-Associative Immune Mediated Hemolytic Anemia: A Prospective Controlled Study in 22 Dogs

BACKGROUND

Urine neutrophil gelatinase-associated lipocalin (uNGAL) is a biomarker for the early diagnosis of AKI.

OBJECTIVES

To evaluate uNGAL in dogs with non-associative immune mediated hemolytic anemia (IMHA) and to evaluate whether uNGAL correlates with disease severity markers, negative prognostic indicators and outcome.

ANIMALS

Twenty-two dogs with non-associative IMHA and 14 healthy dogs.

METHODS

Prospective case-control study. uNGAL was measured by a commercially available ELISA-kit and corrected to urine creatinine (uNGAL to creatinine ratio [UNCR]). uNGAL and UNCR of IMHA cases were compared to that of healthy dogs and the correlation with other clinicopathological markers was evaluated. uNGAL and UNCR were also compared between dogs with a CHAOS or ASA score < 3 and ≥ 3.

RESULTS

uNGAL and UNCR were significantly higher in dogs with IMHA when compared to healthy controls (uNGAL median 114.58 and 0.43 ng/mL, respectively, p < 0.001; UNCR median 174.87 and 0.13 ng/mg, respectively, p < 0.001). uNGAL and UNCR were moderately positively correlated with urea (p = 0.005, r = 0.58, 0.20-0.81 95% CI and p = 0.001, r = 0.64, 0.29-0.84 95% CI, respectively) and total bilirubin (p = 0.003, r = 0.60, 0.22-0.82 95% CI and p = 0.002, r = 0.62, 0.25-0.83 95% CI, respectively). These were also significantly higher in dogs with hemoglobinuria compared to those without (uNGAL: median 269 and 30.99 ng/mL, respectively, p < 0.001; UNCR: median 585.3 and 352 37.47 ng/mg, respectively, p < 0.001). There was no statistically significant difference in uNGAL or UNCR when assessing survival to discharge (p = 0.24 and p = 0.16, respectively, 95% CI).

CONCLUSIONS

This study suggests that renal injury might be underappreciated in dogs with IMHA.

Association of proteinuria at time of diagnosis with survival times in dogs with lymphoma

BACKGROUND

Lymphoma has been implicated as a possible cause of proteinuria in dogs. However, information about the potential importance of proteinuria in dogs with lymphoma is limited.

HYPOTHESIS

To determine if the presence of proteinuria at diagnosis was associated with median survival times in dogs with lymphoma and if lymphoma stage (I-V) or type (B vs T) were associated with the presence of proteinuria.

ANIMALS

Eighty-six client-owned dogs with a new diagnosis of lymphoma between 2008 and 2020.

METHODS

This was a retrospective cross-sectional study with dogs divided into proteinuric or nonproteinuric groups based on dipstick urine protein (protein ≥30 mg/dL classified as proteinuric) or a ratio of dipstick protein to urine specific gravity (ratio ≥1.5 classified as proteinuric). Dogs were excluded for: (1) treatment within 2 months with glucocorticoid, anti-neoplastic, or anti-proteinuric therapies, (2) diagnosed hypercortisolism or renal lymphoma, (3) active urine sediment, or (4) urine pH >8. Survival analysis utilized a Kaplan-Meier estimator and log-rank testing.

RESULTS

There was a significant difference in median survival between proteinuric and nonproteinuric dogs classified by urine dipstick (245 days [91, 399] vs 335 days [214, 456]; P = .03) or UP : USG (237 days [158, 306] vs 304 days [173, 434]; P = .03). No difference in prevalence of proteinuria was identified between stages (I-V) or types (B and T).

CONCLUSIONS AND CLINICAL IMPORTANCE

Proteinuria appears to be negatively associated with survival time in dogs newly diagnosed with lymphoma.

Clinical manifestations of chronic pancreatitis in English cocker spaniels

BACKGROUND

Chronic pancreatitis (CP) is common in English cocker spaniels (ECS). It is histologically similar to IgG4-related disease (IgG4-RD) in humans and is characterized by duct destruction, interlobular fibrosis, and dense periductular and perivenous lymphocytic aggregates. However, the clinical manifestations of CP in ECS have not been previously described.

OBJECTIVES

Characterize the clinical manifestations of CP in a group of ECS, including similarities and differences to IgG4-RD in humans.

ANIMALS

One-hundred four ECS with CP and 44 client owned control ECS without CP (both healthy and diseased controls).

METHODS

Affected dogs were divided into 2 groups according to the methods used to diagnose CP. Case records were searched for signalment, clinical, and clinicopathological findings, and evidence of keratoconjunctivitis sicca (KCS), proteinuria, other immune-mediated diseases, and anal sacculitis.

RESULTS

Involvement of other organs was common. Affected ECS presented with a high frequency of KCS (n = 49), proteinuria (n = 47), anal gland disease (n = 36), atopy (n = 21), and other immune-mediated diseases (n = 16). Those with parti-color hair coats, particularly blue roan, had a strong association with CP, suggesting a link between coat color and autoimmune conditions in this breed.

CONCLUSIONS AND CLINICAL IMPORTANCE

English cocker spaniels with CP show clinical similarities to humans with IgG4-RD and common involvement of other organs. Clinicians should evaluate affected Cocker Spaniels for proteinuria, keratoconjunctivitis sicca, and other potential immune-mediated diseases.

Evaluation of a urine dipstick protein to urine specific gravity ratio for the detection of proteinuria in dogs and cats

BACKGROUND

The utility of urine dipsticks for the quantification of proteinuria is limited because of the influence of urine specific gravity (USG). To circumvent the need for urine protein creatinine ratios (UPCR) some have proposed a calculated dipstick urine protein to USG ratio (DUR) for the detection of proteinuria. However, the performance of DUR has not been evaluated in veterinary patients.

OBJECTIVES

Evaluate the correlation between DUR and UPCR, while also assessing the effect of urine characteristics on this relationship and evaluating the performance of DUR in detecting proteinuria.

ANIMALS

Urine samples from 308 dogs and 70 cats.

METHODS

Retrospective cohort study of urinalyses and UPCRs from dogs and cats collected between 2016 and 2021.

RESULTS

Both canine and feline urine samples showed a positive moderate correlation between the UPCR and DUR. The correlation was not influenced by the presence of active urine sediment, glucosuria, or urine pH. In detecting canine urine samples with a UPCR >0.5, an optimal DUR of 1.4 had sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 89%, 83%, 96%, and 63%, respectively. In detecting feline urine samples with a UPCR >0.4, an optimal DUR of 2.1 had sensitivity, specificity, PPV, and NPV of 70%, 100%, 100%, and 75%, respectively.

CONCLUSIONS AND CLINICAL IMPORTANCE

Use of the DUR can be a relatively reliable method for identification of proteinuria. However, given its poor NPV, the DUR cannot be recommended for exclusion of proteinuric patients.

The relationships between sediment findings and culture results and the presence of proteinuria in canine urine samples

OBJECTIVES

To assess relationships between urine sediment and microbial culture findings and the presence of proteinuria in canine urine samples, and to assess the change in the percentage of proteinuric samples and urine protein-to-creatinine ratio when urine abnormalities resolve.

MATERIALS AND METHODS

Canine urine samples collected via cystocentesis and submitted for culture and contemporaneous urinalysis (including urine protein-to-creatinine ratio) were retrospectively identified. Dogs receiving corticosteroids were excluded. Associations between haematuria (red blood cells>5/high-power field), pyuria (white blood cells>5/high-power field), presence of microorganisms on microscopy, active sediment, and positive culture and proteinuria (urine protein-to-creatinine ratio>0.5) were investigated. Patient characteristics were considered possible confounders. In dogs with repeat urinalysis, the associations between active sediment and positive culture resolution on proteinuria and urine protein-to-creatinine ratio were assessed.

RESULTS

One hundred and ninety-two of 491 samples were proteinuric (39.1%). Age was positively associated with proteinuria. In the multivariable analysis corrected for age, active sediment was the only variable significantly associated with proteinuria (adjusted odds ratio: 2.12; 95% confidence interval: 1.44 to 3.11); however, only 49.8% of samples with active sediment were proteinuric. Neither resolution of active sediment nor positive culture were associated with reduced proportions of proteinuric samples (from 57.9% to 42.1% and from 40.0% to 25.0%, respectively) or significant reductions in urine protein-to-creatinine ratio (median change: -0.16 and -0.14, respectively).

CLINICAL SIGNIFICANCE

Attributing proteinuria to urinalysis abnormalities or a positive urine culture in canine cystocentesis samples is not supported by our findings, and could result in alternative causes of proteinuria (e.g. renal proteinuria) being overlooked.

The utility of clinicopathological findings and point-of-care ultrasound in increasing the index of suspicion of ureteral obstruction in azotaemic cats presenting to the emergency room

OBJECTIVES

Ureteral obstruction is a common post-renal cause of azotaemia in cats. The objective of this study was to describe clinicopathological and point-of-care ultrasound findings in azotaemic cats that may increase the index of suspicion of ureteral obstruction.

MATERIALS AND METHODS

A retrospective case-control study was conducted of azotaemic cats presenting to the emergency room of a referral teaching hospital. Cats were included if they were azotaemic and had point-of-care ultrasound and formal ultrasound performed. Cats were grouped into obstructed and non-obstructed groups based on formal specialist ultrasound and pyelography. Point-of-care ultrasound findings were described, including renal size and symmetry, renal pelvis dilation, perinephric fluid, and visualisation of the proximal ureter or calculi. Univariate analysis was performed to identify historical, biochemical and point-of-care ultrasound findings associated with ureteral obstruction before multivariate analysis.

RESULTS

One hundred twenty-two azotaemic cats met the inclusion criteria. Seventy-four cats were included in the obstructed azotaemic group and 48 cats in the non-obstructed azotaemic groups. Point-of-care ultrasound abnormalities were detected in 60 of 74 (81.1%) obstructed cats and 18 of 48 (37.5%) non-obstructed cats. Renal pelvis dilation (odds ratio 38.8; 95% confidence interval 2.9 to 515), hyporexia (odds ratio 5.9; 95% confidence interval 1.15 to 30.13), hypercalcaemia (odds ratio 16.6; 95% confidence interval 1.2 to 223.0) and hypokalaemia (odds ratio 21.7; 1.33 to 354.62) were more likely to be associated with ureteral obstruction than non-obstructive disease.

CLINICAL SIGNIFICANCE

Point-of-care ultrasound abnormalities are documented frequently in azotaemic cats with ureteral obstruction. Cats with renal pelvis dilation were 39 times more likely to have ureteral obstruction than non-obstructive acute kidney injury.

Proteomic research on new urinary biomarkers of renal disease in canine leishmaniosis: Survival and monitoring response to treatment

The objective of our study was to search for survival biomarkers (SB) and treatment response monitoring biomarkers (TRMB) in the urinary proteome of dogs with renal disease secondary to canine leishmaniosis (CanL), using UHPLC-MS/MS. The proteomic data are available via ProteomeXchange with identifier PXD042578. Initially, a group of 12 dogs was evaluated and divided into survivors (SG; n = 6) and nonsurvivors (NSG; n = 6). A total of 972 proteins were obtained from the evaluated samples. Then, bioinformatic analysis reduced them to 6 proteins like potential SB increased in the NSG, specifically, Haemoglobin subunit Alpha 1, Complement Factor I, Complement C5, Fibrinogen beta chain (fragment), Peptidase S1 domain-containing protein, and Fibrinogen gamma chain. Afterwards, SG was used to search for TRMB, studying their urine at 0, 30, and 90 days, and 9 proteins that decreased after treatment were obtained: Apolipoprotein E, Cathepsin B, Cystatin B, Cystatin-C-like, Lysozyme, Monocyte differentiation CD14, Pancreatitis-associated precursor protein, Profilin, and Protein FAM3C. Finally, enrichment analysis provided information about the biological mechanisms in which these proteins are involved. In conclusion, this study provides 15 new candidate urinary biomarkers and an improved understanding of the pathogenesis of kidney disease in CanL.

[Urinalysis in dogs and cats, part 1: physical and chemical urinalysis]

The urinalysis of dogs and cats is an important part of the diagnostic evaluation of urinary tract diseases as well as for the identification of systemic diseases. A routine urinalysis consists of a physical and chemical examination of the urine as well as an examination of the urine sediment. Various urine collection methods (free-catch, catheterization, cystocentesis) are available. Each method has multiple advantages and disadvantages. The appropriate method must be chosen individually for each patient depending on the emphasis of the examination. The urine should ideally be examined within 30 minutes of collection as it is prone to change due to time and storage. Physical examination of the urine consists of the determination of urine color, clarity, and specific gravity which provides information regarding the concentration of the urine. The latter is determined by refractometry and needs to be interpreted in the context of the hydration status of the patient. Chemical examination of the urine consists of the determination of the pH value and the presence of blood/hemoglobin/myoglobin, protein, glucose, bilirubin, urobilinogen, nitrite, and ketones. The use of commercially available urine dipsticks is common. These must be stored and used according to the manufacturer's instructions and when interpreting the results, veterinary aspects need to be taken into consideration. The physical and chemical examinations of the urine represent rapid and readily performable methods that provide important information for the diagnosis or the exclusion of numerous diseases.

Evaluation of haem dipstick pad, urine protein, urine pH and urine protein:creatinine ratio results as a marker of bacteriuria in dogs and cats with inactive urine sediment

OBJECTIVES

Evaluation of haem dipstick pad, urine protein, urine pH and urine protein:creatinine ratio results as a marker of bacteriuria in dogs and cats with inactive urine sediment.

MATERIALS AND METHODS

Cats and dogs with contemporaneous urine dipstick, microscopic sediment analysis and microbiological culture and sensitivity results over a four-year period (2016 to 2020) were retrospectively identified. Dogs and cats with active urine sediments (at least five erythrocytes and/or five leukocytes per high-power field) and/or spermaturia were excluded. Association between urine pH, haem dipstick result, protein dipstick result and urine protein:creatinine ratio with bacteriuria were evaluated using binary logistic regression analysis. Likelihood ratios for bacteriuria were calculated at different diagnostic thresholds.

RESULTS

A total of 668 and 169 dog and cat urine samples were included. Of these, 166 dogs (25%) had a positive urine culture, whilst only 29 cats (17%) had a positive urine culture. In dogs and cats, any positive haem dipstick result was significantly associated with bacteriuria, although only a ≥4+ haem positive result in dogs was associated with a small increase in the likelihood of a positive urine culture, and positive likelihood ratios did not support the use of haem dipstick results as a screening test for bacteriuria in cats. pH, urine protein:creatinine ratio and protein dipstick results were not associated with bacteriuria.

CLINICAL SIGNIFICANCE

Our findings provide proof of concept that haem dipstick pad results in dogs with inactive sediment and without spermaturia might be useful as a screening test for bacteriuria, although further studies are required to confirm these findings.

Evaluation of a rapid immunoassay for bacteriuria in dogs

BACKGROUND

The ability to detect bacteriuria in dogs with a point-of-care test might improve medical care and antimicrobial stewardship.

HYPOTHESIS AND OBJECTIVE

A rapid immunoassay (RIA; RapidBac) will provide acceptable sensitivity and specificity for diagnosis of bacteriuria.

ANIMALS

Forty-four client-owned dogs with a clinical indication for urinalysis and aerobic bacterial urine culture.

METHODS

Prospective study. Urine, collected by cystocentesis, was submitted for urinalysis and culture at a diagnostic laboratory. Owners completed an enrollment questionnaire regarding their dogs' clinical signs. The RIA was performed according to the manufacturer's guidelines. Results were compared to culture.

RESULTS

Forty-four urine specimens were evaluated from 44 dogs. The sensitivity and specificity of the RIA test to detect bacteriuria compared to urine culture were 81.8% (95% CI, 65.7%-97.9%) and 95.5% (95% CI, 86.8%-99.9%), respectively. For cultures yielding ≥10³  CFU/mL, sensitivity increased to 90.0% (95% CI, 76.9%-100%) and specificity was similar at 95.2% (95% CI, 86.1%-99.9%). Malodorous urine, bacteriuria, and pyuria were more likely to be present in dogs with positive RIA or urine culture results compared to dogs with negative results.

CONCLUSIONS AND CLINICAL IMPORTANCE

The RIA was easy to perform and had good sensitivity and excellent specificity in this group of dogs. The RIA might be a useful screening test for decision-making regarding antimicrobial therapy in dogs with a clinical indication for urine culture. Consideration could be given to amending the International Society for Companion Animal Infectious Disease definition of bacterial cystitis as the presence of signs of lower urinary tract disease together with positive culture or a positive RIA.

The effect of non-absorbent hydrophobic sand litter on the urine protein-to-creatinine ratio in feline urine

Background

Proteinuria can be quantified through the measurement of the urine protein‐to‐creatinine ratio (UPC). Voided urine samples in cats are often exposed to a non‐absorbable litter substrate prior to collection and urinalysis. Little is known about the effect exposure to such substrates has on pre‐analytical variability of UPC measurements.

Objectives

The aim of this study was to assess agreement between UPC measurements from urine obtained by cystocentesis before and after exposure to non‐absorbent hydrophobic sand for 24 hours.

Methods

UPCs were measured in 40 urine samples obtained by cystocentesis from 39 cats (baselineUPC). Urine was then exposed to non‐absorbent hydrophobic sand litter for 24 hours, recovered, and repeat UPCs were measured (litterUPC). Agreement between paired measurements and the presence of any bias or error was evaluated using Bland–Altman analysis Passing–Bablok regression analysis, respectively. Cohen's kappa was used to measure agreement for the International Renal Interest Society (IRIS) proteinuria classification of samples. Observed total error (TE_obs) was calculated for the laboratory analyzer and compared against absolute percentage changes in paired UPC measurements.

Results

Neither proportional nor constant error was identified using Passing‐Bablok regression between baselineUPC and litterUPC. Visual inspection of the Bland–Altman plot revealed good agreement, with 95% of paired measures falling within the limits of agreement (LOA). Cohen's kappa demonstrated almost perfect agreement for the IRIS classification of proteinuria between baselineUPC and litterUPC. Absolute percentage changes of paired UPC measurements outside of the LOAs were lower than the inter‐assay TE_obs.

Conclusions

Feline urine exposed to non‐absorbent hydrophobic sand litter appears acceptable for UPC measurements.

Prevalence of positive urine culture in the presence of inactive urine sediment in 1049 urine samples from dogs

Background

Urinalysis (UA) is often used to screen for bacterial cystitis, regardless of sediment results, and followed up by quantitative urine culture (UC) for definitive diagnosis.

Objectives

Determine prevalence of positive UCs in dogs with inactive urine sediments on routine UA.

Animals

A total of 1049 urine samples with inactive urine sediments and UCs collected from dogs presented to a veterinary specialty hospital between January 2018 and February 2020.

Methods

Retrospective study of dogs with an inactive urine sediment on routine UA and follow‐up UCs. Signalment, UA findings, proteinuria, and UC results were recorded. Associations among these findings were assessed using multivariate logistic regression carried out using a backward stepwise method.

Results

Overall prevalence of positive UC was 3.4% (95% confidence interval [CI], 2.4‐4.8). Escherichia coli was the most commonly isolated bacteria. Only naturally voided samples were associated with increased prevalence of positive culture when compared to collection by cystocentesis or a non‐specified method. No statistically significant association with culture positivity was found for urine protein‐to‐creatinine ratio, urine specific gravity, urine pH, breed, age, or sex.

Conclusions and Clinical Importance

Based on the low prevalence (3.4%) of positive culture in urine samples from dogs with inactive sediment on routine UA and the relatively high cost of UC and sensitivity, cost‐benefit analysis including clinical suspicion of lower urinary tract disease should inform testing decisions, rather than routinely performing cultures on urine samples without active sediments.

Characteristics associated with bacterial growth in urine in 451 proteinuric dogs (2008-2018)

Background

Urine cultures are frequently recommended to rule out infection as a postrenal cause of proteinuria.

Objective

Identify characteristics associated with bacterial growth in urine in proteinuric dogs.

Animals

Four hundred and fifty‐one dogs admitted to a teaching hospital between January 2008 and January 2018 with urine protein‐to‐creatinine ratios (UPCs) >0.5.

Methods

Retrospective study included dogs with a UPC, urinalysis, and quantitative urine culture (QUC) performed within a 72‐hour period by searching electronic records. Dogs with recent antimicrobial therapy, urine collected by methods other than cystocentesis, or UPC ≤0.5 were excluded. Signalment, comorbidities, serum BUN and creatinine concentrations, urinalysis findings, and QUC results were recorded. The association between these characteristics and presence of bacterial growth in urine was assessed by univariable and multivariable analysis.

Results

Thirty of four hundred fifty‐one dogs (6.7%) had bacterial growth in urine. Of these, 18 (60.0%) had active urine sediment. Bacterial growth in urine was associated with pyuria (odd ratio [OR] 25.1, 95% confidence interval [CI] 7.9‐79.6, P < .001), bacteriuria (OR 11.1, 95% CI 3.2‐39.1, P < .001), and lower urinary tract disease (OR 6.7, 95% CI 1.9‐23.0; P = .0028). If QUC was prompted based on these criteria, 8/451 (1.8%) of proteinuric dogs would have had undetected bacterial growth.

Conclusions and Clinical Importance

The proportion of proteinuric dogs with both inactive urine sediment and bacterial growth in urine was low, suggesting that QUC might not be necessary in the evaluation of all proteinuric dogs. An active urine sediment or lower urinary tract disease should prompt QUC for proteinuric dogs.

Influence of preanalytic and analytic variables in canine and feline urine specific gravity measurement by refractometer

Urine specific gravity (USG), which is usually measured by refractometry, is an important indicator of renal concentrating ability. Few studies have evaluated refractometers with separate scales for canine and feline urine. Variables such as protein content or storage time may influence the USG. We compared the effects of measuring USG with a refractometer with single or separate scales for canine and feline urine, investigated inter- and intra-observer variability, and measured agreement between whole urine and supernatant. We evaluated the correlation between USG and osmolality, the influence of urinary protein on USG and osmolality, and the impact of storage time up to 6 mo. We examined 252 canine and 126 feline samples. Bland-Altman analysis revealed higher USG values of the single-scale refractometer than the dual-scale refractometer, with a mean difference (bias) of < 0.001 for canine and 0.003 for feline specimens. Inter- and intra-observer variability were acceptable. Good agreement was shown between USG of whole urine and supernatant. Correlations between USG and osmolality were excellent (0.98-0.99, p < 0.001). Proteinuria up to 1 g/L had no major impact on USG or osmolality. Storage time had no significant effect on USG. The difference between the refractometers is clinically irrelevant, and the use of a refractometer with separate feline and canine scales is unnecessary. Whole urine and supernatant stored up to 6 mo can both be used for USG measurement. The influence of proteinuria <1 g/L on USG and osmolality is negligible.

Relationships among urinary protein-to-creatinine ratio, urine specific gravity, and bacteriuria in canine urine samples

Background

Proteinuria is a marker of chronic kidney disease in dogs and a risk factor for increased morbidity and death. Predictive models using the results of readily available screening tests could foster early recognition.

Objective

To determine whether urine specific gravity (USG) and semiquantitative category of dipstick protein can be used to predict urinary protein‐to‐creatinine ratio (UP : C) and to examine the effect of urine culture results on UP : C in dogs.

Animals

Three hundred ninety‐four dogs (482 visits) presented to a university Community Practice Clinic or Veterinary Teaching Hospital between January 2011 and November 2015.

Methods

Retrospective study. Medical records were searched to identify dogs for which urinalysis, UP : C measurement, and urine culture testing were performed during a single hospital visit. Urine specific gravity, UP : C, dipstick protein concentration, and findings of urine sediment analysis and urine culture were recorded. Regression or Spearman correlation analysis was used to test for relationships between UP : C and USG within dipstick categories and between UP : C and bacterial colony‐forming units per milliliter, respectively. Cohen's kappa test was used to evaluate agreement between urine culture and UP : C testing.

Results

There were significant (P < .05) weak negative correlations (R² range, 0.14‐0.37) between UP : C and USG for all nonnegative urine protein dipstick categories. The presence of a positive urine culture did not agree with the presence of abnormal UP : C (κ = −0.06).

Conclusions and Clinical Importance

Within dipstick protein categories, UP : C cannot be accurately predicted from USG. Repeating UP : C measurement after resolution of urinary tract infection is advisable.