EVALUATION OF THE RELATIONSHIP BETWEEN ULTRASONOGRAPHIC KIDNEY DIMENSIONS AND MODIFIED BODY MASS INDEX IN CLINICALLY HEALTHY NIGERIAN INDIGENOUS DOGS

ABSTRACTS

Ultrasonography was used to determine the correlation between the kidney dimensions in 115 clinically healthy Nigerian Indigenous Dogs (NID) with anthropometric indices such as Modified Body Mass Index (mBMI) and sex. In-vivo ultrasonographic kidney dimensions were obtained by measuring the kidneys’ length, width and height to compute the kidney volume using prolate ellipsoid formula (L x W x H x 0.523) while anthropometric dimensions were measures of body weight and truncal length to obtained the modified body mass index (mBMI) for dogs (body weight/truncal length²). The result showed that the right kidney length of clinically healthy NID was within the range of 3.86 – 7.40 cm with the mean of 5.54 ± 0.067, while the left kidney length was 4.12 – 7.57 cm with the mean of 5.81 ± 0.062. The right kidney width was within the range of 1.86 – 5.00 cm with the mean of 3.15 ± 0.056, while the range for left kidney width was 2.04 – 5.42 cm with the mean of 3.36 ± 0.049. The right kidney height was within the range of 1.77 – 4.40 cm with the mean of 2.79 ± 0.045, while the range for left kidney height was 1.84 – 4.64 cm with the mean of 3.10 ± 0.052. Correlation between modified body mass index and kidney dimensions revealed a significant but weak positive relationship in right and left kidney length (0.30 and 0.37), kidney height (0.22 and 0.18) respectively, and right kidney volume (0.21), while there were no significant correlation in right kidney width (0.083) and left kidney volume (0.18), but a negative correlation was revealed in left kidney width (-0.057). The values for the variations between males and females in right and left kidneys respectively included: kidney length (0.3001 and 0.4274), kidney width (0.5465 and 0.7045), kidney height (0.0294 and 0.6421) and kidney volume (0.0834 and 0.6727). The values for the differences between the right and left kidneys in males and females respectively included: kidney length (0.0008 and 0.0012), kidney width (0.0226 and 0.007), kidney height (0.0004 and 0.0001) and kidney volume (0.0004 and 0.0001). The right kidney volume of clinically healthy NID was within the range of 9.22 – 63.20 cm with the mean of 26.33 ± 0.94, while the left kidney volume was 13.66 – 70.21 cm with the mean of 32.36 ± 1.04. In conclusion, the mean values of the right and left kidney dimensions in NID are kidney length as 5.54 ± 0.067 cm and 5.81 ± 0.062 cm, kidney width as 3.15 ± 0.056 cm and 3.36 ± 0.049 cm and kidney height as 2.79 ± 0.045 cm and 3.10 ± 0.052 cm respectively; correlation between kidney dimensions and modified body mass index (mBMI) was a positive linear relationship except for the left kidney width that was a negative linear relationship; there were no statistically significant differences in kidney dimensions between male and female but left kidney appeared larger than the right kidney in both male and female; the mean values of right and left kidney volume were 26.33 ± 0.94 and 32.36 ± 1.04 respectively.

CHAPTER ONE

INTRODUCTION

1.1 Background of the Study

Ultrasonography is an excellent modality for examining abdominal structures including the location and dimensions of canine kidneys (Remichi et al., 2014). It involves a non-invasive procedure for examination of kidney diseases (Sampaio and Araujo, 2002) and offers advantages over radiography as there are no side effects of radiation and contrast agents (Nyland et al., 1995). Canine kidneys are located in the retroperitoneal region of the abdomen around T₁₂-L₁ for right kidney and L₁-L₃ for left kidney (Burk and Feeney, 2003). The kidneys perform various important functions in the body such as excreting waste products, maintaining homeostasis, blood production and utilization of mineral such as calcium (Fitzgerald et al., 2011). The left kidney is situated caudal to the stomach, dorsal and medial to the spleen by the side of the left side of the abdomen, ultrasonographic visualization of the left kidney can be achieved at this point by gently dragging the transducer craniocaudal on longitudinal plane, if the left kidney is cited, kidney length can be obtained from the cranial and caudal poles of the image, then rotate the transducer at 90⁰ anti-clockwise to transverse plane where the width of the left kidney can be measured along hilus positioned at the medial border to the lateral border of the kidney, then again the height of the left kidney can also be measured on the same transverse plane from the dorsal border down to the ventral border of the kidney. While right kidney is more cranially located than left kidney, having contact cranially with the caudate lobe of the liver, its ultrasonographical measurement can be obtained just as described as that of the left kidney (Nyland and Matton, 2002). Researchers were able to use these kidney dimensions to determine the kidney volume which is a useful measurement in the diagnosis of kidney diseases (Barrera et al., 2009).

Many kidney disorders are associated with changes in kidney dimensions (Sohn et al., 2016) for instance chronic interstitial nephritis causes a decrease in kidney size while acute pyelonephritis, polycystic kidney disease and hydronephrosis results in renomegaly (Jeyaraja et al., 2015). Invariably, kidney length is the most important tool used in determining kidney size (Konde et al., 1984), so changes in kidney length, as well as other dimensions, indicate abnormal kidney function which is used in the diagnosis of kidney diseases (Sohn et al., 2016). Generally, a normal range for some canine kidney dimensions have been established (Ast, 2002), however, some researchers are of the opinion that normal range for canine kidney dimensions should be based on individual breed because of body size disparity among numerous breeds of dogs (Lobacz et al., 2012). Other important laboratory parameters used in the diagnosis of kidney diseases include total protein, calcium, sodium, phosphate, potassium, creatinine, blood urea nitrogen and albumin (Bush, 1993; Needham, 2005; Kovarikova, 2015; Arora and Batuman, 2016). Body mass index is a diagnostic tool used in ascertaining the prevalence of obesity, overweight and thinness in a human population (Cole and Lobstein, 2012). It is a representative of body adiposity (Gallagher et al., 1996; Pasco et al., 2014). Body mass index is a commonly used diagnostic tool to analyse obesity and overweight based on weight and height (Murguia-Romero et al., 2012).Body mass index measurement was introduced by Lambert Adolphe Jacques Quetelet (1842) to explain the connection between body weight and stature in humans, until recently, researchers were able to discover the usefulness of body mass index in estimating body fats (Deurenberg et al., 1991). WHO (2000) set cut-off points for body mass index for human as less than 18.5 kg/m² for underweight, greater than 18.5 kg/m² to less than 25 kg/m² for normal weight, greater than 25 kg/m² to less than 30 kg/m² for overweight and greater than 30 kg/m² for obesity. Body mass index has been considered as health indicator because overweight and obesity are implicated as consequence of metabolic syndrome (Murguia-Romero et al., 2012). There is a strong linkage between overweight and obesity with conditions such as osteoarthritis, gout, gallbladder disease (DerSarkissian, 2016) as well as cancer of various organs including kidney cancer in human (Bhaskaran et al., 2014). In Veterinary practice, a modified body mass index for dogs was been suggested due to the difference in body shapes between human and dogs (Thengchaisri et al., 2014). NID are unclassified, they belong to the medium size breed of dogs with unique predominant features such as average body size and moderate hair coat with mesocephalic cranial index. The possible classification of dogs presently in Nigeria is indigenous and exotic breeds of dogs those imported into the country such as German shepherd, Rottweiler, Mastiff, Cocker spaniel, Chihuahua, Maltese, Lhasa Apso, Pitbull, Bull Dog and cross breeds of different degree between these breeds ( Oluwatoyin and Fayemi, 2011).

1.2 Statement of Research Problem

NID are erroneously called “mongrels’’ with little-classified information of the breed itself. There is a paucity of information on kidney dimensions of NID which their clinical importance cannot be over emphasized.

Several studies have shown that kidney dimensions vary among the breed of dogs (Lobacz et al., 2012). Therefore, there is a need to investigate the kidney dimensions in NID, as it is considered a useful tool in the accurate diagnosis of kidney diseases (Sohn et al., 2016).

Kidney dimensions in veterinary practice can be related to useful anthropometric indices such as modified body mass index (mBMI), age, breed, body weight and these relationships are known to be useful in diagnosis of nephropathy (Barr et al., 1990; Park et al., 2008; Huaijantug et al., 2016). Therefore, there is a need to investigate the relationship between the kidney dimensions and modified body mass index (mBMI) in NID.

1.3 Justifications of the Study

A better understanding of this breed necessitates establishing data such as kidney dimensions as well as the modified body mass index (mBMI) which both has clinical relevance. Kidney volume can also serve as a prognostic biomarker in monitoring progress in kidney diseases (Sharma et al., 2017).

Knowledge of the relationship between kidney dimensions and modified body mass index (mBMI) will assist clinicians in the accurate morphological diagnosis of kidney disorders in dogs, as inference on kidney function can be deduced from the evaluation of modified body mass index (mBMI) in NID. This relationship is also very useful in kidney transplantation, as it gives the surgeon the best transplant match between the donor’s kidney and recipient’s metabolic demands (Oh et al., 2005).

1.4 Aim of the Study

The broad aim of the present study is to determine the kidney dimensions using ultrasonography and to correlate with anthropometric indices such as modified body mass index (mBMI) and sex in clinically healthy NID.

1.5 Objectives of the Study

The specific objectives of the study were to:

1. Determine the kidney dimensions such as length, width and height in the clinically healthy NID using ultrasonography.
2. Correlate the kidney dimensions at ultrasonography with the modified body mass index (mBMI) in clinically healthy NID.
3. Determine the sex differences in kidney dimensions and variation between right and left kidneys at ultrasonography, in clinically healthy NID.
4. Establish the kidney volume using the ellipsoidal method of clinically healthy NID.

1.6 Research Questions

1. What are the values of kidney dimensions in the clinically healthy NID?
2. What is the relationship between kidney dimensions and modified body mass index (mBMI) in clinically healthy NID?
3. Are there sex disparities in kidney dimensions between right and left kidneys at ultrasonography in clinically healthy NID?
4. What are the average kidney volume values in clinically healthy NID?

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