Introduction
Kidneys are a pair of bean-shaped organs that filter wastes from the body. A healthy kidney normally filters approximately half a cup of blood each minute to remove waste and excess water. The kidneys help to maintain a balance between water, electrolytes, and minerals in the blood. They also produce hormones that regulate blood pressure, make blood cells, and keep the body healthy. The kidney consists of a basic unit called nephrons, which help filter waste. The nephron is made of a filter called a glomerulus (that filters blood) and a tubule (which returns substances to blood and eliminates waste). Obesity has had a tremendous impact on the metabolic system. Recent studies show the effect of obesity on renal functions as well.
What Is a Fatty Kidney?
Fatty kidney simply refers to fat in the renal (kidney) parenchyma. Studies show that obesity has played an important role in developing chronic kidney diseases as well. Recent research by the World Health Organization (WHO) shows that the prevalence of obesity is over 40 percent among adults in the United States. When the body mass index (BMI) is over 30, it is considered obese. Fat deposition in the visceral tissues has been found to have consequences on various organs in different ways.
A fatty kidney is a very common medical condition and is often associated with an increased risk of chronic kidney disease or CKD (a condition in which the kidneys are no longer able to filter blood, leading to complete kidney damage) and hypertension (high blood pressure). Obesity has been known to affect the cardiovascular and metabolic systems. In addition, recent research shows the effect of obesity on causing renal dysfunction. A higher body mass index is found to have a strong association with chronic kidney diseases.
Body Mass Index (BMI) is calculated based on a person’s height and weight and gives an overall idea of the fatty tissue in the body. However, it does not provide information on the pattern of fat deposition if the adipose tissue is more in the abdominal area, which can be a risk factor for chronic kidney conditions. The kidneys are surrounded by visceral adipose tissue (VAT) and can cumulate the adipose in the renal sinus.
What Are the Symptoms of Chronic Kidney Disease (CKD)?
Kidney diseases do not present symptoms in their early stages and usually get diagnosed in urine or blood tests for other medical conditions. However, in its advanced stage, symptoms present are as follows:
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Shortness of breath.
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Tiredness.
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Blood in urine.
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Swelling in feet, hands, and ankle.
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Feeling sick.
How Does Obesity Affect the Kidneys?
Being obese can cause many metabolic abnormalities and have an effect in increasing the risk of kidney diseases. It is still not very clear as to how exactly obesity causes kidney diseases, though a strong association between the two has been established. Some kidney diseases may be worsened by comorbidities like hypertension or diabetes (high blood glucose). The effects of obesity can impact the kidneys directly by endocrine activation. These can include inflammation, oxidative stress (an imbalance of the production and accumulation of oxygen-reactive species), abnormal lipid metabolism, and increased insulin production and resistance.
These effects can bring about pathologic changes in the kidneys that can cause kidney diseases. Ectopic lipid accumulation, increase in renal sinus fat, glomerular hypertension (which occurs due to the reduction in the number of functional nephrons), and increased glomerular permeability, leading to glomerulomegaly (abnormal enlargement of glomeruli) or glomerulosclerosis (scarring of the glomerulus or kidney filters). Recent studies show that glomerulomegaly caused by obesity has increased ten times between 1988 and 2000. The resultant condition is called obesity-related glomerulopathy (ORG).
What Is Obesity-Related Glomerulopathy(ORG)?
Obesity-related glomerulopathy is found to lead to conditions like chronic kidney disease, end-stage renal disease, and, occasionally, death. ORG may go unnoticed for many years and not show evident clinical presentations. It is usually diagnosed later when the renal functions are affected and the prognosis is poor. Strategies to identify high-risk patients should be considered, which can help to identify the condition early and take necessary treatments and precautions.
Oligonephronia (reduced glomerular density) and glomerulomegaly or glomerular hypertrophy are the main characteristic lesions in the histopathology of ORG. Glomerular hypertrophy is due to functional adaptations (which are represented by glomerular hyperfiltration). The reduced density of the glomerulus can be due to renal damage, leading to glomerulomegaly and increased glomerular pressure.
The main clinical presentation of the condition includes proteinuria (protein in urine). This can be accompanied by normal urinary sediment. Despite the increased proteinuria (increased protein levels in urine) values, it is interesting that these patients usually do not develop hypoalbuminemia (a reduced protein level in the body).
How Is Fatty Kidney Diagnosed?
Normal imaging modalities like magnetic resonance imaging (MRI) and computed tomography (CT) cannot identify the fat deposition in the kidneys. The renal cortical fat deposits are measured using Proton MRI. Advancements in imaging modalities like ultrasound, MRI, and CT can help in the early diagnosis of the condition in the future. Ultrasound elastography (in which sound waves are used to send vibrations in the liver) of the kidneys can be used to measure the fat in the kidneys.
How Is Fatty Kidney Managed?
Standard management of the condition has yet to be discovered. The initial management includes the prevention of obesity through changes in lifestyle and diet. Regular exercise and a healthy diet can help reduce the condition's incidence. Regular evaluation of kidney functions at regular intervals must be done in obese people. Any deviation from the normal must be assessed and treated accordingly. Management in the final stages will be difficult and have a poor prognosis.
Conclusion
A sedentary lifestyle has caused many lifestyle diseases and metabolic conditions. The worldwide epidemic of obesity has caused a variety of diseases. Fatty liver and fatty kidney are some of them. It has affected the quality of life and increased morbidity and mortality. Following a healthy diet and regular exercise is important to avoid such conditions. The healthcare sector should plan a strategy to monitor the upcoming generations for signs of obesity. Those who are obese should be monitored for systemic diseases. Treatment must be started in the initial phases for a better prognosis. This can, in turn, pave the way for a better and healthy tomorrow.
