Comprehensive clinical, hematobiochemical, urinary, and ultrasonographic profiling of canine chronic kidney disease: A multimodal diagnostic evaluation

Introduction

Chronic kidney disease (CKD) is a multifactorial clinical syndrome that represents the end stage of a gradual pathological deterioration affecting one or more components of the nephron, including the glomeruli, tubules, interstitium, and vasculature (Brown, 2007) [2] . According to Polzin et al. (2011) [22] , CKD is defined as the presence of structural or functional abnormalities in one or both kidneys persisting for at least three months. The likelihood of developing this progressive disorder increases with advancing age (Perez et al., 2018) [18] . CKD is characterised by varying degrees of architectural distortion within the renal parenchyma, which may occur with or without overt clinical signs of functional impairment (Constantinescu et al., 2015; Al-Janabi, 2024) [3,17] . Persistent proteinuria is recognised as one of the most significant risk factors contributing to the increased morbidity and mortality associated with CKD (Jacob et al., 2005) [9] . The predominant clinical manifestations of uraemia include gastrointestinal disturbances such as reduced appetite, vomiting, halitosis, oral ulcerations, uraemic stomatitis, tongue tip necrosis, and melena or haematochezia. Additional common signs comprise depression, lethargy, weight loss, cachexia, hypertension, and anaemia (Kumar et al., 2020; Tufani et al., 2017) [14,33] . Urine output may vary depending on the underlying cause and stage of the disease (Sheeran, 2021; Mishra, 2019) [27,35] . Ultrasonography serves as an essential diagnostic modality for identifying structural abnormalities of the kidneys. Combined evaluation of blood and urine parameters plays a critical role in the early detection of renal dysfunction. Importantly, normal serum creatinine values do not necessarily indicate normal renal function. More sensitive indicators of glomerular filtration rate (GFR) including plasma creatinine clearance, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), urinary microalbumin, urinary protein-to-creatinine ratio (UPCR), and urine albumin-to-creatinine ratio (UACR) offer greater diagnostic utility, although limitations may restrict their routine clinical use (Singh, 2017) [28] . The present study outlines the prevalence of CKD in dogs and documents the associated haematological and biochemical alterations observed in cases presented to the Veterinary Clinical Complex, Khanapara, during a six-month study period.

Material and Methods

Criteria for Inclusion in Animal Selection

The study was conducted over a six-month period at the Veterinary Clinical Complex, College of Veterinary Science, Khanapara, Assam, and included dogs presented from various regions of Assam and neighboring northeastern states. Dogs of any age, breed, or sex showing clinical signs indicative of chronic kidney disease (CKD) including inappetence, vomiting, altered urination, polydipsia, anemia, lethargy, diarrhea, and oral lesions were screened through physical examination, hematological analysis, serum biochemical profiling, ultrasonography, and urinalysis to confirm CKD (Brown et al., 2007) [2] .

Sample collection

On day 0 (pre-treatment), 2 mL of blood was collected into a K₂-EDTA vial and 3 mL into a clot-activator Vacutainer for hematological and biochemical analyses. Additionally, 20-25 mL of urine was aseptically collected by catheterization using an appropriately sized infant feeding tube for routine examination.

Evaluation of Hematological and Serum Biochemical Parameters

Hematological analyses were performed using an automated hematology analyzer (MS4Se, MELET SCHLOESING Laboratories) to determine WBC count (m/mm³), RBC count (M/mm³), hematocrit (Hct, %), and hemoglobin (Hb, g/dL). Serum biochemical parameters were assessed using a clinical auto-analyzer (Idexx Catalyst One), which measured creatinine, blood urea nitrogen (BUN), total protein, albumin, phosphorus, calcium, potassium, sodium, and chloride concentrations.

Urine analysis

Urine samples were evaluated using Nucleus Diagnostics Nuvision test strips with the Nuvision urine strip analyzer. Color and clarity were assessed visually, followed by analysis of pH, urine specific gravity (USG), urine protein, urine creatinine, and microscopic sediment examination. The urine protein-to-creatinine (UPC) ratio was calculated using the formula: Urine protein and creatinine (UPC) ratio = Urinary Total protein (mg/dl) Urinary creatinine (mg/dl)

Ultrasonography

A color Doppler ultrasound system (ACUSON NX3 Elite, Siemens Healthineers) was used to evaluate renal architectural changes in dogs with CKD. Both a 5-8 MHz convex probe and a 3.5-10 MHz linear probe were employed for abdominal imaging. Data analysis: Statistical analysis of the experimental data was carried out using two-way ANOVA (SAS Enterprise Guide 9.3 version).

Results

In the present study, out of 3, 180 registered dogs, 40 were confirmed to have CKD based on clinical history, physical examination, hematobiochemical findings, urinalysis, and ultrasonographic evaluation, yielding an overall prevalence of 1.25%. The distribution of CKD cases by breed, age, and sex is shown in Figures 123and tables 1-4. Labrador Retrievers, male dogs, and those aged 6-10 years were the most frequently affected groups.

Clinical Signs

The most frequently observed clinical signs were inappetence, oral lesions, vomiting, polyuria, and polydipsia. The full distribution of clinical manifestations recorded in the study is presented in Table 5 and Figure 4.

Haematology

Different hematological parameters WBC, RBC, Hct, and hemoglobin of healthy control and CKD-affected dogs are presented in Table 6. In the present study, a highly significant (P<0.01) increase in the Mean±SE of WBC count was observed in CKD-affected dogs (24.22±3.28) compared with healthy controls (12.06±0.67). Although the Mean±SE values of RBC, Hb, and Hct in CKD-affected dogs (RBC: 12.06±0.67; Hb: 11.23±0.47; Hct: 36.73±1.58) showed a decreasing trend relative to healthy controls (RBC: 6.67±0.27; Hb: 12.14±0.49; Hct: 41.57±1.63), these differences were not statistically significant (p>0.05).

Serum Biochemistry

The biochemical parameters serum creatinine, BUN, total protein, albumin, phosphorus, calcium, potassium, sodium, and chloride of healthy control and CKD-affected dogs are presented in Table 7. A highly significant (P<0.01) increase in the Mean±SE values of serum creatinine (5.13±0.60) and BUN (60.68±5.40) was observed in CKD-affected dogs compared with healthy controls (creatinine: 1.14±0.04; BUN: 16.10±0.95). Serum phosphorus (7.84±0.25) and potassium (5.33±0.22) levels were also significantly elevated (P<0.05) relative to controls (4.68±0.20 and 4.37±0.21, respectively). A significant (P<0.05) decrease in serum albumin (1.46±0.06) and chloride (109.37±1.17) was recorded in CKD-affected dogs compared with healthy values (2.55±0.036 and 114.00±0.92, respectively). In contrast, no significant (P>0.05) differences were observed in total protein (7.14±0.12), calcium (9.16±0.16), and sodium (148.12±0.89) when compared with the corresponding control values (7.84±0.25, 9.53±0.21, and 149.75±0.92, respectively).

Urine analysis

Urine parameters including color, pH, specific gravity, urine protein, urine creatinine, and UPC ratio are presented in Table 8. In CKD-affected dogs, urine ranged from amber to deep amber and was mostly turbid or translucent, whereas urine from healthy controls appeared colorless to pale yellow and clear. Urine pH (6.85±0.10) and specific gravity (1.010±0.004) in CKD dogs showed no significant differences compared with healthy controls (6.83±0.26 and 1.006±0.002, respectively). Microscopic examination of CKD urine samples revealed crystals (triple phosphate, calcium oxalate, uric acid), RBCs, WBCs, epithelial cells, and occasional casts (figs 5, 6 & 7).

Nephrosonographic alterations in kidneys of CKD dogs

A nephrosonogram was performed on CKD-affected dogs to evaluate alterations in renal architecture and echogenicity. The sonographic findings are summarized in Table 9 and illustrated in Figures 8 &9.

Discussion

In the present study, the prevalence of chronic kidney disease (CKD) among dogs was 1.25%, which was lower than the rates reported by Tufani et al. (2015) [32] and Karunanithy et al. (2019) [12] , who recorded 2.58% and 2.22%, respectively. These variations may reflect differences in population size, study duration, case load, diagnostic criteria, and screening protocols across studies. Among the affected breeds, Labrador Retrievers showed the highest prevalence (0.64%), consistent with earlier findings (Tufani et al., 2015; Joshi et al., 2021) [32,10] . Their predisposition may be attributed to a higher risk of systemic diseases such as cardiovascular disorders and diabetes, which serve as important comorbid risk factors for CKD. Male dogs (0.84%) were more commonly affected than females (0.41%), which aligns with previous reports (Athaley, 2018; Meena et al., 2022) [1,16] . This sex-related difference may be due to an increased predisposition of males to urolithiasis and prostate-related disorders, which can impede urine flow (Katoch et al., 2017; Kumar et al., 2020) [13,14] . Behavioral factors such as heightened aggression and increased catecholamine release may further predispose males to cardiovascular stress, an additional risk factor for CKD. Age-wise distribution showed the highest occurrence in dogs aged >6-10 years (0.72%), in agreement with earlier studies (Devipriya et al., 2018; Reddy et al., 2021) [4,24] . Advancing age is strongly associated with decreased nephron number, reduced renal blood flow, and impaired tubular function, all of which contribute to CKD progression (Polzin, 1990; Grauer & Lane, 1995) [21,6] . The clinical signs observed such as inappetence, vomiting, polyuria, polydipsia, diarrhoea, oral lesions, weight loss, and lethargy were characteristic of renal insufficiency and consistent with previously documented patterns (Kumar et al., 2020; Sheeran, 2021) [14,27] . Inappetence and vomiting may be attributable to the accumulation of uremic toxins and altered secretion of appetite-regulating hormones like leptin and ghrelin. Vomiting may also result from stimulation of the chemoreceptor trigger zone, decreased gastrin clearance, and increased gastric acidity (Tufani et al., 2017; Kumar et al., 2020) [33,14] . Diarrhoea could be linked to uremic enterocolitis associated with advanced uremia (Polzin, 2011) [22] . Weight loss and lethargy likely stem from inadequate caloric intake, malabsorption, and the catabolic effects of uraemia. Pale mucous membranes likely reflect reduced erythropoietin secretion, while mucosal congestion may be due to dehydration. Polyuria and polydipsia arise from compromised urine-concentrating ability (Polzin, 2010) [23] , and oral ulceration and halitosis may be caused by urease-positive oral bacteria converting urea into ammonia or direct mucosal irritation from uremic toxins (Grauer, 2009; Kumar et al., 2020) [6,14] . Hematological analysis revealed a significantly elevated WBC count in CKD-affected dogs, which may indicate systemic inflammation, urinary tract infections, or immune activation due to circulating uremic toxins (Sonu et al. 2018; Gupta et al. 2022) [29,7] . Although RBC, Hb, and Hct values showed a decreasing trend, the changes were not statistically significant. These reductions are expected in CKD due to impaired erythropoietin secretion, shortened RBC lifespan, and nutritional deficiencies, but the non-significant differences may reflect early disease stages or compensatory mechanisms. Serum biochemical findings showed a highly significant increase in serum creatinine and BUN, confirming reduced glomerular filtration and azotemia, characteristic of CKD (Sumit et al., 2018) [30] . Serum phosphorus and potassium were significantly elevated, owing to reduced renal excretion. Hyperphosphatemia contributes to secondary hyperparathyroidism and accelerates nephron damage, while hyperkalemia poses cardiovascular risks due to its effects on cardiac electrical activity (Ribeiro et al. 2020 and Thade et al. 2021) [25,31] . A significant decrease in serum albumin may result from protein-losing nephropathy, chronic inflammation, or malnutrition or due to increased filtration of albumin through glomeruli, owing to its molecular size (Shaw and Ihle, 2013) [26] , while reduced chloride likely reflects electrolyte imbalance or metabolic acidosis due to dehydration, vomiting, polyuria, diarrhea and inadequate water consumption occurred in the majority of the CKD affected dogs (Thade et al., 2021) [31] . Total protein, calcium, and sodium levels did not differ significantly, which is consistent with the compensatory mechanisms that often maintain these parameters within normal ranges during early or moderate CKD. Urinalysis showed that CKD-affected dogs commonly had amber to deep amber, turbid urine, which may indicate dehydration, cellular debris, or poor filtering ability (Kaneko et al., 2008) [11] . Urine pH and specific gravity did not differ significantly between CKD and control dogs, possibly due to variability in hydration status and disease stage (Yadav et al. 2020) [34] . Microscopic examination revealed the presence of crystals (triple phosphate, calcium oxalate, uric acid), RBCs, WBCs, epithelial cells, and occasional casts. These findings suggest renal tubular damage, inflammation, or secondary urinary tract infections. The increased urine protein-to-creatinine (UPC) ratio confirmed proteinuria, a key indicator of glomerular dysfunction and a predictor of CKD progression (Singh, 2017; Polzin, 2011) [28,22] . Ultrasonographic examination demonstrated changes such as altered renal size, increased cortical echogenicity, and loss of corticomedullary distinction, which are commonly associated with chronic renal damage. These findings correlate with nephron loss, interstitial fibrosis, and progressive architectural distortion of the kidneys, as described by Grauer, 2009; Kumar et al. 2011 and Perondi et al. 2020 [6,14,19] .

Conclusion

The study concludes that chronic kidney disease remains a significant health concern in dogs, with a prevalence of 1.25%. Breed susceptibility, male sex, and advancing age were key contributing factors. The combined evaluation of clinical signs, hematological changes, biochemical alterations, urine abnormalities, and ultrasonographic findings offers a reliable approach for diagnosing CKD. Early identification through routine screening particularly in high-risk breeds and older dogs supports timely intervention, slows disease progression, and enhances the quality of life in affected animals. Continued emphasis on awareness, preventive care, and regular renal monitoring is crucial for effective CKD management in veterinary practice.

Acknowledgement

AcknowledgementThe authors thank the Veterinary Clinical Complex, College of Veterinary Science, Khanapara, for providing necessary facilities and support, and extend their gratitude to the pet owners for their cooperation.

References

1. Athaley AJ. Comparative therapeutic efficacy of polyherbal combinations in renal failure in dogs [MVSc thesis]. Nagpur: Maharashtra Animal and Fishery Sciences University; 2018.
2. Brown S. Management of chronic kidney disease. In: BSAVA manual of canine and feline nephrology and urology. 2007. p. 223-230.
3. Constantinescu R, Crivineanu V, Goran G, Nae RT, Codreanu MD. Evaluation of renal vascular resistance and blood pressure in dogs with different renal diseases. Sci Work Ser C Vet Med. 2015;61:178-183.
4. Devipriya K, Lavanya C, Selvaraj P, Napolean RE. Early diagnosis of renal insufficiency in dogs with haemato-biochemical findings. J Entomol Zool Stud. 2018;6(5):703-705.
5. Grauer GF. Measurement, interpretation, and implications of proteinuria and albuminuria. Vet Clin North Am Small Anim Pract. 2007;37:283-295.
6. Grauer GF, Lane IF. Acute renal failure: Ischemic and chemical nephrosis. In: Osborne CA, Finco DR, editors. Canine and Feline Nephrology and Urology. Philadelphia: Lea & Febiger, Williams & Wilkins; 1995. p. 441-459.
7. Gupta R, Jena GR, Jena BR, Chandra R. Clinical, haemato-biochemical and oxidative changes associated with chronic kidney disease (CKD) in dogs. Pharma Innov J. 2022;SP-11(11):1575-1579.
8. Ignatescu RM, Goanta AM, Badulescu AM, Braslasu D, Ionita L. Clinical and therapeutical approach to protein-losing nephropathy in dogs: A review. Sci Work C Vet Med. 2019;65(1):51-59.
9. Jacob F, Polzin DJ, Osborne CA, Neaton JD, Kirk CA, Allen TA, et al. Association between initial proteinuria and morbidity or death in dogs with chronic renal failure. J Am Vet Med Assoc. 2005;226:393-400.
10. Joshi. Studies on early diagnosis of chronic kidney disease in dogs and its therapeutic management [MVSc thesis]. Anand: Anand Agricultural University; 2021.
11. Kaneko JJ, Harvey JW, Bruss ML, editors. Clinical biochemistry of domestic animals. New York: Academic Press; 2008. p. 28.
12. Karunanithy N, Thakur N, Dey S. Prevalence of renal disorders in dogs of Bareilly area of Uttar Pradesh, India. Biol Rhythm Res. 2019;52:116-126.
13. Katoch A, Wadhwa DR, Sharma A. Epidemiological observations on canine renal disorders. Himachal J Agric Res. 2017;43(2):135-138.
14. Kumar C, Kamran C, Isloor S. Clinical signs observed in different stages of chronic kidney disease in dogs. Int J Livest Res. 2020;10(10):249-252.
15. Kumar V, Kumar A, Varshney AC. Ultrasonographic imaging for structural characterization of renal affections in 10 dogs. ISRN Vet Sci. 2011;2011:901713.
16. Meena P, Bargujar J, Nagar JK, Meena A, Bhardwaj SK, Choudhary S, et al. Occurrence of renal failure in Labrador dogs and relation with age, sex and body weight. Pharma Innov J. 2022;SP-11(5):1412-1414.
17. Al-Janabi SM. Morphohistological study of kidney in local cow (Bos taurus) in middle of Iraq. Zool Entomol Lett. 2024;4(2):92-96.
18. Perez-Gomez MV, Martin-Cleary C, FernandezFernandez B, Ortiz A. Meso-American nephropathy and genetic influence on CKD development. Clin Kidney J. 2018;11(4):491-495.
19. Perondi F, Lippi I, Marchetti V, Bruno B, Borrelli A, Citi S. Ultrasound usefulness for staging CKD in dogs: Findings in 855 cases. Vet Sci. 2020;7(4):147.
20. Polzin DJ. Chronic kidney disease. In: Polzin D, Bartges J, editors. Nephrology and urology of small animals. 1st ed. Oxford: Blackwell Publishing Ltd.; 2011. p. 433-471.
21. Polzin DJ. The effects of aging on the canine urinary tract. Vet Med. 1990;85:472-482.
22. Polzin DJ. Chronic kidney disease. In: Polzin DJ, Bartges J, editors. Nephrology and Urology of Small Animals. Oxford: Blackwell Publishing Ltd.; 2011. p. 433-471.
23. Polzin DJ. Chronic kidney disease. In: Ettinger S, Feldman E, editors. Textbook of Veterinary Internal Medicine. St. Louis: Saunders; 2010. p. 1990-2021.
24. Reddy AK, Lakshmi K, Ambica G, Kumar BA. Incidence of chronic kidney disease in dogs. Pharma Innov J. 2021;SP-10(7):738-740.
25. Ribeiro JFA, Liguori TTA, Le Sueur ANV. Biochemical profile, urinalysis, UPC, electrolytes and blood pressure in dogs with CKD: A transversal study. Acta Sci Vet. 2020;48:1733.
26. Shaw DH, Ihle SL. Small animal internal medicine. Hoboken: John Wiley & Sons; 2013. p. 628.
27. Sheeran. Diagnostic and therapeutic studies on renal failure in dogs [MVSc thesis]. Jammu and Kashmir: Sher-e-Kashmir Univ Agric Sci Technol; 2021.
28. Singh S. Early diagnostic and prognostic markers of chronic kidney disease in dogs [MVSc thesis]. Ludhiana: GADVASU; 2017.
29. Sonu AK, Charaya G, Bangar Y, Agnihotri D, Kumar T. Haemato-biochemical alterations in dogs with chronic renal failure. Indian J Vet Med. 2019;39:31-35.
30. Sumit GP, Kumar P, Gulia D, Jhambh R, Sindhu N, Chaudhary RN. Haemato-biochemical and serum electrolyte alterations in dogs with CKD. Pharma Innov J. 2018;7:302-306.
31. Thade GC, Bhojne GR, Dhoot VM. Successful management of chronic kidney disease in dogs. Indian J Canine Pract. 2021;13(2):54-57.
32. Tufani NA, Singh JL, Kumar M, Gupta D, Shekhar P, Rajora VS. Renal failure in Indian dogs: An epidemiological study. Indian J Vet Med. 2015;35(1):711.
33. Tufani NA, Singh JL, Kumar M, Rajora VS. Diagnostic evaluation of renal failure in canine with special reference to urinalysis. J Entomol Zool Stud. 2017;5(6):2354-2364.
34. Yadav SN, Ahmed N, Nath AJ, Mahanta D, Kalita MK. Urinalysis in dog and cat: A review. Vet World. 2020;13(10):2133-2141.
35. Mishra P. Studies on diagnosis and therapeutic management of chronic kidney diseases in dogs [MVSc thesis]. Kolkata: West Bengal University of Animal and Fishery Sciences; 2019.