Influence of Age Breed and Sex on Incidence of Renal Disorders in Dogs

Kidneys are paired vital organs, which play an essential role in health, disease and growth. These are the complex organs with many functions. Renal disorders are among the most common ailments of dogs and contribute substantially to canine mortality, particularly in older dogs. In a survey, the Australian veterinary practitioners reported 1-2 cases per two weeks of renal disorders in dogs. (Watson et al., 2001). A British survey indicated that 0.2% of dogs were presented with suspected renal diseases, out of which 25% were confirmed. There was no evidence of breed or sex predisposition (Mac Dougall et al.,  1986). However, the frequency of renal disorders in dogs increases with age and nearly 15% of dogs above 10 years were reported to have renal diseases  (Polzin et al., 1989). Fewer published reports are documenting the prevalence of renal diseases in dogs in India (Mrudula et al., 2005; Ponnuswamy et al., 2009). Hence, a preliminary study was carried to find out the incidence of the renal disorder in dogs at Referral Veterinary Poly Clinic, IVRI, Izatnagar, Bareilly, India.

Clinical cases of dogs reported at the Referral Veterinary Polyclinic, Indian Veterinary Research Institute during the period from February 2010 to January 2011 were investigated for the presence of renal disorders based on clinical signs, biochemical changes in blood and urine, and ultrasonographic examination. The animals diagnosed for renal disorders were subsequently grouped according to age, breed and sex to find the influence of these variables on the occurrence of the condition.

Animals were subjected to extensive clinical examination and were given a clinical score calculated based on clinical signs like anorexia (1 point), lethargy (2 points), vomiting (3 points), diarrhoea (4 points), weight loss (5 points), polyuria (6 points), polydipsia (7 points), pallor (8 points) and/or ulceration of mucous membrane (9 points), and neurologic signs (10 points). The dogs with a score of 6 and above were subjected for ultrasonographic examination and blood and urine biochemical estimations.

Ultrasonographic (USG) examination of sick animals, as well as healthy dogs, was carried out using SONOSITE-600M MACHINE as per the procedure described by Nyland et al., (2000) using 2.5-5 MHz transducer for both the kidneys. Healthy control dogs were subjected to fasting for 12 hours. However, owners were advised to give ad libitum quantity of water. The sick dogs with the clinical signs of the renal disorder as mentioned earlier in the clinical examination were not subjected to fasting. The cranio-ventral abdominal hairs were shaved from costal arch cranially to the inguinal region caudally and laterally along the body wall. Acoustic coupling gel was applied liberally over the abdomen to provide essential acoustic coupling of the transducer to the patient. The animals were gently restrained in dorsal recumbency by holding the forelimbs. No anaesthesia or chemical restraint was used.

Blood samples were collected in clean vials from 10 healthy dogs and all those diagnosed for renal disorders. These were allowed to clot and serum was harvested and stored at -20°C till used for biochemical estimations consisting of serum urea nitrogen (Marsh et al., 1965), creatinine (Bonses and Taussky, 1945) and gamma-glutamyl transferees (Jung et al., 1986).

The urine samples from healthy and sick dogs have collected aseptically from the urinary bladder by using a urinary catheter for estimation of N-acetyl-β-D-glucosaminidase (NAG) as per the method described by Maruhn (1976). Briefly, p-nitrophenyl-N-acetyl-β-D-glucosaminide (1.5 mmol/l: 1 ml) was incubated with urine (0.1 ml) which had been diluted with 0.15 mol/l citric acid-disodium phosphate buffer (0.5 ml, pH 4.5 or 4.1) for 30 minutes at 37°C. Enzyme hydrolysis was stopped by the adding 0.5 mmol/l sodium carbonate-bicarbonate, pH 10 (0.5 ml). Colour intensity was measured at 405 nm on a double beam spectrophotometer and enzyme activity was measures using a standard curve prepared over the range 5 to 50 µmol/l.

The total numbers of 880 cases of dogs suffering from different ailments were reported during this period, out of which 63 dogs were suspected and screened for renal disorders based on clinical signs, ultrasonographic findings, serum and urinary biochemical alterations and urine analysis. Out of 63 cases of renal disorders, 44 cases showed the symptoms of anorexia, lethargy, polyuria, polydipsia, weight loss, vomiting and pallor mucous membrane, 11 cases with ulceration of mouth and 8 cases with neurological signs along with other signs of renal disorders were recorded.

Apart from the above signs, 7 animals also presented signs denoting complications viz. skin lesions marked by alopecia, ecchymosed and mange infestation. Rectal temperature (101± 0.4°F), heart rate (94±18 bpm) and respiratory rates (28±6/minute) were found normal in all the animals. However, abdominal palpation evidenced a sign of pain in 5 cases.
 
Age-wise distribution
 
Distribution of renal disorders according to age is given in Table 1 and Fig 1. The overall incidence of renal disorders was 7.15%. No renal disorders were detected in the dogs < 6 years of age whereas only 6 dogs (3.26%) of 6-8 year age group were confirmed for kidney diseases. The incidence of renal disorders was increased with the advancement of age as 16 (9.30%) and 41 (13.94%) dogs in the age groups of 8 -10 year and ≥10 years, respectively The highest incidence of renal disorders was seen in dogs of age group 10 years and above. No renal disorders were detected in the dogs < 6 years of age and only 6 dogs (3.26%) of 6-8 year age group were confirmed for kidney diseases.





The frequency of renal disorders increases with the age in dogs, as inhuman (Cowgill and Sprangler, 1981; Gobar et al., 1998; McCall Kaufman, 1984). In another report prevalence of renal diseases in the US, university hospital was observed in 15% of dogs more than 10 years of age (Polzin et al., 1989). The age has an important role in the incidence of the renal disorder in canines (Nabi et al., 2018). This might be because with the advancing age, blood flow to the kidneys decreases and there is a loss of filtering cells (nephrons). The resorption processes in the nephrons are also impaired with advance age. All these factors contribute to greater chances of renal dysfunction (Polzin, 1990; Grauer and Lane, 1995). In human beings, a slight decrease in GFR and concentrating ability were observed with age. Morphological changes observed in association with ageing in human being include shrinkage of nephron size after 40 years of age (Finco, 1997).
 
Breed and sex-wise distribution
 
The breed wise distribution of renal disorders in dogs is shown in Table 2 and Fig 2. The highest incidence was noted in Labrador dogs (12.19%), followed by Bulldogs (11.11%), Dalmatian (10.53%), Great Dane and Rottweiler (9.09%), Doberman (7.86%), German Shepherd (6.73%) and Pomeranian (6.45%). Interestingly lowest incidence was recorded in the mixed or non-descript breed (6.12%).

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The sex-wise incidence of renal disorders in dogs is depicted in Table 2 and Fig 3. Out of 63 dogs, 36 male (57%) and 27 female (43%) dogs were confirmed for renal disorders indicating a higher prevalence of renal diseases in males than females.

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The breed wise distribution of renal disorders showed the highest incidence of renal disorders in Labrador and lowest in mixed or non-descript dogs while the sex wise occurrences of renal disorders were 57% in male and 43% in female dogs. However, a British survey indicated that 0.2% of dogs were presented with suspected renal disease, which was confirmed in 25% of the cases with no evidence of breed or sex predisposition (Mac Dougall et al.,  1986) and in another report it was observed that no predisposition of sex has been found in the occurrence of renal disorders in canine (Tilley and Smith, 2007). The female and descript breeds of dogs are having more incidence of renal disorders than male and nondescript breeds (Nabi et al., 2018). The lowest incidence of renal disorders in mixed or non-descript dogs might be due to their genetic makeup to sustain the ageing effects on the kidney. However, further investigations involving large population size is warranted to substantiate this finding.

It is concluded that the increased occurrence of renal disorder was recorded with the advancement of the age of dogs. Male dogs are suffering from kidney disorder more commonly as compared to female dogs. The highest incidence of renal disorder was observed in Labrador dogs followed by Bulldogs, Dalmatian, Great Dane and Rottweiler, Doberman, German Shepherd, and Pomeranian, while the lowest incidence was recorded in the mixed or non-descript breed as compared to the specific breed of dogs.

The authors are highly thankful to the Director, Joint Director (Academics) and Head Division of Veterinary Medicine, Indian Veterinary Research Institute, Izatnagar, Bareilly (UP) India, for providing funds and necessary facilities in carrying out the present research work.