Introduction
Some diseases are more common in one species than others, which may lead to the underdevelopment of research areas, leading to the lack of sufficient information about health problems. This is evident for the condition commonly called fatty liver, otherwise known as hepatic steatosis (or lipidosis) (Washabau and Day 370). According to the statistics, this disease is widespread in cats but is rather rare in dogs (Hirose et al. 1015). Nonetheless, as canines can develop this condition as well, the studies in this area have to be considered. This research paper analyzes the knowledge surrounding the issue of hepatic steatosis in dogs and reveals a dearth of knowledge pertaining to the disease’s impact on dogs’ gastrointestinal (GI) tract.
Background
Hepatic lipidosis is a disorder characterized by abnormally high lipid levels in one’s liver that can be a part of an injury or a response to another problem. Considering the microscopic evaluation, one can describe two main types – micro-and macrovesicular steatosis. In macrovesicular steatosis, the most common form of this disease, the hepatocyte nucleus is smaller than the vacuoles. As a result, the latter displaces the nucleus in the cell, moving it to the periphery (Washabau and Day 370-371). In the microvesicular type of steatosis, there are many fine vacuoles that, while not displacing the nucleus, fill the cytoplasm (Washabau and Day 370-371). The lipid vacuoles’ location leads to increased lipid accumulation, which can result in the liver acquiring a yellowish color. With high amounts of lipids, the liver can also grow in size.
To start the examination, it is vital to discuss the pathophysiology of the disease as well as its risk factors, predeterminants, and causes. As a primary condition, hepatic steatosis in dogs remains poorly examined – the leading cause of the issue is unclear. Still, some other problems increase one’s risk of having a fatty liver. To begin with, most studies highlight the impact of starvation on one’s liver. When a dog does not receive sufficient nutrition for a prolonged period, the fatty acids from fat stores are mobilized at an increased rate. At the same time, the production of lipid-transporting proteins is reduced. In turn, the triglycerides are not moved from the liver, and hepatic disposition occurs.
Small dogs from toy breeds are in a risk group of developing hepatic steatosis due to their incidence of anorexia. They can develop anorexia as a response to stress due to vaccination, surgery, change of ownership, and other causes. Furthermore, small dogs have small muscle mass and high metabolic energy requirements. The limited hepatic gluconeogenesis leads to hypoglycemia that, with the lack of attention, can lead to fatty liver disease (Partner).
Dogs of all breeds may be at risk of steatosis if they have a high-fat and low-protein diet. A poorly balanced intake of protein leads to the altered synthesis of lipoproteins and disturbs the movement of very-low-density-lipoproteins (VLDLs) from the liver (Takahashi et al. 2030). This process may also be induced by other conditions such as diabetes mellitus and pancreatitis. Currently, the treatment of lipidosis includes dietary change – meals with high protein levels and control overhydration and fat intake are prioritized.
The lack of knowledge about the processes of hepatic lipidosis leads to small amounts of research on this disease’s link to other health problems. For instance, it is clear that fatty liver is detrimental to the health of the dog’s GI tract, but the transparent connection between various conditions is not drawn (De Marco et al. 719). Primary research discussed below shows that the discussion in the current scholarship revolves around the successful diagnosis of hepatic steatosis and the impact of this disease on congenital problems such as portosystemic shunts.
Primary Research Summary
As the research in the field of canine hepatic steatosis is concentrated on the diagnosis and evaluation of the disease, the selected primary studies reflect this basic amount of knowledge. The first article by Zemlyanskyi considers how biochemical parameters of a dog’s blood serum can support the diagnosis of hepatic lipidosis. The author notes that primary and secondary lipidosis produces different lipid diagrams for dogs, thus urging to define the nature of changes in the animals’ bodies (Zemlyanskyi 26). Moreover, the author states that the lack of diagnostic tests performed in the local veterinary practice ignores the fact that abnormal findings of lipid metabolism can tell much about the progression of the disease.
The scholar’s main goal was to determine whether the results of lipid metabolism evaluation supported the diagnosis and strengthened findings of fatty liver. The author investigated dogs of different breeds and ages that had similar wights and nutrient plans, dividing the samples into animals with and without clinical pathology. Zemlyanskyi successfully proves that such findings as total cholesterol, triacylglycerol, cholesterol VLDL, and other elements of the lipid diagram and their change during treatment are highly useful for analysis (29). In the discussion section of the research, the author suggests a process that leads to the development of fatty liver, explaining the metabolic changes and their effect on the dog’s systems.
Apart from that, the scholar provides an important insight into the connection between the health of dogs’ liver and their GI tract health. For example, while symptoms vary from one dog to another significantly, it is clear that most animals experienced pain, constipation, anorexia, vomiting, violated gastrointestinal motility, and other related symptoms (Zemlyanskyi 27). This information, although not directly related to the author’s conclusions, opens the discussion of the connection between lipidosis and GI tract problems. Nonetheless, the scholar’s sample of dogs is highly inconsistent in the prevalence of symptoms, which indicates that the research into this topic is very complicated.
The next primary research study by Hunt et al. considers the development of hepatic steatosis in dogs that were born with portosystemic shunts (CPS). The scholars aim to compare the results of the evaluation of the canines with CPS and dogs without this condition, focusing on their lipid profiles. Notably, both groups of dogs are reported to have hepatic steatosis, meaning that this study’s purpose is to detect the ways in which these conditions affect each other.
Here, one can see a topic that is currently somewhat researched in the field of hepatic lipidosis – the effect of congenital portosystemic shunts on the dog’s liver and vice versa (Van den Bossche 2). The scholars collect biopsy samples from dogs with and without CPS and observe the number of large and small liver droplets. In the end, Hunt et al. note that there exists a significant difference between the two groups, and hepatic lipidosis can have a substantial impact on the shunt and its surgical attenuation (1112).
This study is notable for its step outside of focusing on the diagnosis of lipidosis and an attempt to connect the disease of the liver with other conditions in dogs. Nonetheless, Hunt et al. pay more attention to the congenital condition rather than the unique impact of steatosis on dogs’ bodies. Therefore, while the difference is noted, it is not explained as to what particular influence one’s fatty liver has on other organs.
Discussion
The state of the research described above reveals many black spaces in people’s knowledge about canine hepatic lipidosis. First of all, although the mechanisms of the disease are present in literature, their underlying reasons are hardly explained, leaving one with many questions about the processes of primary steatosis. Second, the increased risk of toy breed gods being susceptible to this condition is supported by studies that are more than 20 years old (Washabau and Day 370). Therefore, the dated research available to veterinarians may not assist them in treating animals.
On the other hand, contemporary research is still limited to studies that aim to diagnose hepatic lipidosis better than before. However, the tests used in these articles are similar to those appearing in older sources. Current studies do not look at dogs, in particular, preferring to analyze liver problems in other animals (Hirose et al. 1015). This lack of attention to canine steatosis leaves out many investigations that could be conducted using the technology and science available today. For example, the proposed area of examination – the connection between fatty liver and GI tract complications- remains as a supplement to studies and not a separate topic of discussion.
Conclusion
Overall, the research on canine hepatic steatosis remains scarce. Veterinarians use data that has not been updated for decades, and new studies focus on diagnostic measures that are not new as well. Complex connections between various conditions, such as fatty liver disease and GI tract problems, are not considered adequately, leaving any blank spaces in one’s knowledge of the issue and its effect on dogs’ health.
Works Cited
Bartner, Lisa. “Hepatic Lipidosis in Toy Breed Dogs.” Indiana Animal Disease Diagnostic Laboratory. Web.
De Marco, Viviani, et al. “Therapy of Canine Hyperlipidemia with Bezafibrate.” Journal of Veterinary Internal Medicine, vol. 31, no. 3, 2017, pp. 717-722.
Hirose, Naoki, et al. “A Retrospective Histopathological Survey on Canine and Feline Liver Diseases at the University of Tokyo between 2006 and 2012.” Journal of Veterinary Medical Science, vol. 76, no. 7, 2014, pp. 1015-1020.
Hunt, Geraldine B., et al. “Evaluation of Hepatic Steatosis in Dogs with Congenital Portosystemic Shunts Using Oil Red O Staining.” Veterinary Pathology, vol. 50, no. 6, 2013, pp. 1109-1115.
Takahashi, Katsuro, et al. “Warm Ischemia and Reperfusion Injury in Diet-Induced Canine Fatty Livers.” Transplantation, vol. 69, no. 10, 2000, pp. 2028-2034.
Van den Bossche, Lindsay, et al. “Aberrant Hepatic Lipid Storage and Metabolism in Canine Portosystemic Shunts.” PloS One, vol. 12, no. 10, 2017, 1-17.
Washabau, Robert J., and Michael J. Day. Canine and Feline Gastroenterology. Elsevier, 2013.
Zemlyanskyi, A. O. “Biochemical Parameters of Blood Serum of Dogs with Hepatic Lipidosis.’ Journal for Veterinary Medicine, Biotechnology and Biosafety, vol. 3, no. 1, 2017, pp. 26-31.