Jun 6, 2018 | Healthy Tips
HOW DO PHYSICIANS TEST YOUR KIDNEY FUNCTION?
By Veeraish Chauhan, MD
A common misconception that people often have is equating urine output to kidney function. Hence, the assumption is that if you are “making urine,” your kidneys are working just fine. However, nothing is further from the truth, and assessing the function of your kidneys requires lab testing and sometimes radiological imaging.
Most people know that getting a stress test is a way to test your heart’s function.
But how do you test your kidney function? You might have heard doctors mention words like “creatinine” or “GFR” when checking how good or bad your kidneys are doing. Although there are a lot of methods by which the kidneys’ performance can be measured, I will explain the ones that are used most often in a clinical setting.
Broadly speaking, you could check kidney function through either:
(1) Blood tests
(2) Urine tests
(3) Radiological imaging
Blood Tests
This is the most common and usually the most reliable method. Doctors will often order tests that could be variously worded like “basic metabolic panel (BMP),” “chem 7,” “renal function panel,” “GFR,” etc. Essentially, what they are measuring is the levels of electrolytes and two other chemicals called blood urea nitrogen (BUN) and creatinine.
BUN measures the amount of nitrogen present in your blood in the form of urea, hence the name BUN! In other words, what we are measuring is the urea level in the blood.
Urea, as you might know, is a nitrogen-containing compound present in the urine of mammals and often used as a fertilizer. Before you conclude that there is fertilizer flowing in your blood, let me make emphasize that industrial grade urea that is used in fertilizers is manufactured artificially. In fact, urea was the first “organic“ (that is, found in nature in living organisms) compound that was artificially synthesized in a laboratory when German scientist Friedrich Wohler synthesized ammonium cyanate in 1828.
BUN: An Imperfect Test
So why do we measure the urea level in the blood? That is because the blood urea level, (or BUN!) depends on the balance between processes that increase its blood level vs. the processes that decrease its blood level. Factors that increase the level of urea in the blood include dietary protein intake, the ability of your liver to synthesize urea, and the rate of normal cell breakdown (medically referred to as “catabolism”) that also leads to urea production. Finally, the process that decreases the urea level in the blood is your kidney’s ability to excrete urea in the urine.
Assuming that the factors that increase urea level stay constant on a day to day basis, you could argue that the urea level in the blood would be most dependent on your kidneys’ functioning. Hence, kidney disease could be detected by an increase in the blood level of urea, or BUN. However, please bear in mind that this is a simplistic explanation, and the BUN levels, as you might have guessed, could be influenced by diet, catabolism, and the liver function.
Creatinine Is a Better Alternative
You thus don’t need to be a medical professional to realize that BUN is but an utterly imperfect test of kidneys’ function, subject to the vagaries of a multitude of other non-renal factors.
So let’s talk about the other chemical I mentioned above: creatinine.
The word “creatinine” comes from the Greek word for flesh, and it is a product of muscle breakdown. Since your muscle mass does not change on a daily basis, the rate of creatinine production is also fairly constant. As creatinine level in the blood builds up (from muscle breakdown), the kidneys do a great job of filtering it out of your system. (A very small, and usually insignificant (unlike urea!) amount of creatinine is reabsorbed by the kidneys, which could technically influence its blood level, but for simplicity, let’s disregard that for now).
Hence, assuming a steady muscle mass, the level of creatinine in the blood should only be influenced by the kidney’s ability to filter it out. Therefore, increase in blood level of creatinine usually implies worse kidney function.
The blood’s creatinine level is hence a useful piece of data that can help physicians estimate the rate at which kidneys filter blood using validated formulas and equations (that we obviously don’t need to worry about here). That rate is referred to as Glomerular Filtration Rate or GFR; a term you might hear physicians throw around a lot when talking about your kidney function. For most average sized people, a normal GFR would lie between 60 to 120 ml/min.
Normal Is Normal for Normal People!
GFR estimation is based on a formula that was designed for average sized normal people. Since the calculation depends on the blood creatinine level, which in turn depends on the muscle mass, it may not be applicable in people in extremes of age (kids, people over 70 yrs), or muscle mass (people with muscle wasting, liver failure, etc). In other words, a creatinine level of 1.2 (considered “normal” as per most lab ranges) might be ok for a muscular person like Arnold Schwarzenegger but could reflect significant kidney disease in a 90-year-old woman. Just like the BUN level, a medical professional should be able to tell when to consider creatinine and GFR levels really abnormal.
Urine Tests
Testing the urine to look for protein or blood, and its chemical composition may help in indicating the presence of kidney disease. Protein or blood should usually not be detectable in urine and are non-specific markers of kidney disease. A physician should determine whether further specific workup and/or a referral to a nephrologist is warranted.
Radiological Imaging
These techniques entail taking pictures of the kidneys using different methods like ultrasound, CT scan, or MRI. This can help in determining the shape and size of the kidneys. The kidneys are smooth bean-shaped organsapproximately 8-14 cm (3-5.5 inches) in size (depending on the person’s size). Most chronic kidney diseases, with some exceptions, tend to distort the kidneys’ architecture and this can be picked up easily on imaging. One might also be ablfe to pick specific causes of kidney disease/dysfunction like stones, obstructions, hydronephrosis, polycystic kidney disease, etc.
Source:
Hall JE, Guyton AC. (2011). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.
Jun 6, 2018 | Healthy Tips
5 COMMON CAUSES OF CHRONIC KIDNEY DISEASE: WHO SHOULD GET TESTED FOR KIDNEY DISEASE?
By Veeraish Chauhan, MD
What could cause a perfectly fine kidney to start working abnormally? What diseases put your kidney’s ability to filter out toxins in jeopardy? These are common questions that my patients have when I tell them about their chronic kidney disease (CKD) diagnosis.
Let’s talk about disease conditions that put you at a risk of developing kidney disease.
These are the very diseases that should make you and your physician keep an eye on your kidney function regularly, and treat it accordingly.
The typical entities that cause kidney damage are often secondary illnesses like diabetes and not intrinsic kidney diseases. This conclusion is based on objective evidence that we can glean from the United States Renal Data System (USRDS) data.
How Common Is Chronic Kidney Disease?
When defined by GFR <60 during 2005–2010, 6.3 percent of US population met the diagnosis of chronic kidney disease, or CKD (compared to 9.3 and 8.5 percent for diabetes and cardiovascular disease, respectively). If, however, we were to include other parameters by which CKD can be defined (like increased protein excretion in the urine, or albumin excretion over 30 mg/day), the prevalence rate for CKD rises to 9.2 percent. In other words, almost one in ten people will have CKD.
Causes of Chronic Kidney Disease
Diabetes has been the undisputed number one risk factor for CKD, with about 40 percent of the patients reporting the illness, both in the periods 1988-1994, and 2005-2010. The contribution of hypertension as a possible cause seems to have risen from low to the mid 20 percent.
Obesity seems to have remained a significant cause, but the contribution from cardiovascular disease seems to have jumped from mid-20s to almost 40 percent. This would make it as prevalent as diabetes as a risk factor. This increase could also be related to a greater diagnosis of cardiovascular disease owing to widespread testing and greater patient recognition.
You might notice that most of these diseases mentioned above are not really stemming from the kidneys. In fact, the kidneys usually bear the brunt of these secondary diseases. These diseases affect the kidney’s function is through different mechanisms which are beyond the scope of this article. Just to give you an idea though, these mechanisms could include an increase in the blood pressure inside the kidney’s filter (glomerulus), which leads to an increased filtration rate. This is called “adaptive hyperfiltration.” In the short term, this is what masks the fact that you actually could have kidney disease since it makes the blood test results “look normal.” In the long term, this is also precisely why the kidneys begin to “burn out” and develop scar tissue. Imagine a car that is being driven continuously at 200 miles/hour.
That car will break down pretty soon, right? This is what happens when diabetes affects your kidney.
So why am I lecturing the readers on the causes of CKD? My intention is to drive home the point that should you have the following conditions, you should consider yourself a person at a high risk for developing kidney disease and make sure that you are tested. Depending on your stage, you may need to be referred to a nephrologist as well for further management. Again to summarize, these conditions are:
- Diabetes mellitus
- Hypertension
- Cardiovascular disease (this could include people who have ischemic heart disease, heart attacks, strokes, peripheral vascular disease, aneurysms, etc.)
- Obesity
- Genetic tendency and risk factors like polycystic kidneys
- Miscellaneous causes like long-standing NSAID (painkiller) use, long-term lead exposure, etc.
Source:
U.S. Renal Data System, USRDS 2013 Annual Data Report: Atlas of Chronic Kidney Disease and End-Stage Renal Disease in the United States, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 2013.
The data reported here have been supplied by the United States Renal Data System (USRDS). The interpretation and reporting of these data are the responsibility of the author(s) and in no way should be seen as an official policy or interpretation of the U.S. government.
Jun 6, 2018 | Healthy Tips
WHEN TO SEE A KIDNEY DOCTOR
What is a Nephrologist and When Should You See One?
By Veeraish Chauhan, MD.
Nephrologists are physicians who specialize in the diagnosis and treatment of kidney disease. What conditions are treated by a kidney doctor, and when is a referral to one of these specialists needed?
Kidney Disease Overview
If you haven’t heard about nephrology (the study of kidney disease) before, it’s not surprising. Chronic kidney disease (CKD) is often referred to as the “silent killer,” as many people have mild symptoms or no symptoms at all when they are diagnosed.
There are many different terms which can be used to describe kidney disease which can add to the confusion. As noted above, Nephrologists are doctors who treat kidney disease, with the Greek term “nephros” meaning kidneys. You may also hear the term renal disease used to describe kidney problems. The term renal comes from the Latin root “renes” which also means kidneys.
What types of medical conditions may affect your kidneys, what are some of the common symptoms, and when you should be referred to a nephrologist? Studies suggest that delaying a visit to a nephrologist can increase your risk of complications or even death, so this is an important question.
Conditions Treated by Kidney Doctors (Nephrologists)
Kidney doctors care for people who a number of different types of kidney disease including:
Acute kidney injury: Acute kidney disease refers to the rapid onset of kidney disease often related to conditions such as shock (reduced blood perfusion of the kidneys), dehydration, or kidney problems related to surgery
Chronic renal failure: Chronic kidney disease can be caused by a number of different conditions (see below)
Kidney stones: There are different types of kidney stones which may or may not cause symptoms
Kidney infections (pyelonephritis): The term “urinary tract infection” refers to a spectrum of conditions ranging from bacteria in the urine, to symptomatic bladder infections, to infection of the kidneys (pyelonephritis)
There is a wide range of medical problems that can affect the kidneys in different ways. Some of the more common conditions which can cause kidney failure include:
Diabetes (diabetic nephropathy): Diabetes is the leading cause of kidney failure in the United States
Kidney disease related to high blood pressure and heart disease (cardiorenal syndrome)
Obesity
Chronic kidney infections
Kidney stones which cause obstruction
Congenital (from birth) kidney problems such as horseshoe kidney
Glomerulonephritis: Glomerulonephritis is an inflammation of the kidneys which can be caused by a number of different processes, including the bacteria which causes strep throat.
Kidney disease related to lupus (lupus nephritis)
Polycystic kidney disease: Cystic kidney disease is hereditary, though the severity of the disease, as well as age of onset, can vary
Autoimmune diseases such as IgA nephropathy
Kidney failure secondary to liver disease (hepatorenal syndrome)
Chronic kidney disease is described by 5 stages based on the severity of the disease. Grade 1 kidney failure refers to a mild disease, whereas grade 5 renal failure usually indicates that dialysis or a kidney transplant will be needed.
In addition to managing kidney problems (trying to correct the condition or prevent it from worsening), kidney doctors manage the symptoms often associated with kidney diseases, such as electrolyte disturbances (especially problems with potassium levels) and high blood pressure.
Symptoms of Kidney Disease
In order to understand the more common symptoms of kidney disease, it’s helpful to review the structure and function of the kidneys. Your kidneys are located on your flanks, near your spine. Injuries to your back or side below your diaphragm may cause injuries to your kidneys.
Your kidneys perform several important functions. These include filtering your blood to remove toxins, maintaining the proper levels of electrolytes (such as sodium and potassium) to ensure proper functioning of your cells, and maintaining fluid balance in your body.
If you become dehydrated, your kidneys initially work to restore the fluid status to your body, but kidney injuries may occur with prolonged or severe dehydration. If your kidneys are not functioning properly, the level of sodium and potassium in your body may be affected. Electrolyte problems with kidney disease can be serious, Since the right amount of potassium is necessary for proper functioning of your heart, kidney problems may result in abnormal heart rhythms.
Abnormal blood pressure, whether high or low can result in kidney damage. Kidney damage, in turn, can cause problems with regulating your blood pressure.
The kidneys are also responsible for making a hormone involved in the production of red blood cells. For this reason, kidney disease can result in anaemia, a lower red blood cell count.
Some people have urinary problems, such as difficulty urinating. Occasionally people also have flank pain, due to the location of the kidneys. Kidney stones may herald themselves with severe pain which has been likened to childbirth but can be present without pain as well.
Nonspecific or vague symptoms are common, and a reason why you should see your doctor even if you can’t precisely identify your symptoms. These may include fatigue, insomnia, or a metallic taste in your mouth.
Early on with kidney disease, and sometimes even with advanced kidney disease, people may have few symptoms. In fact, the most common symptom of kidney disease is no symptoms at all!
Diagnosing Kidney Disease
There are several different types of tests which can be done to screen for and follow kidney problems. These include blood tests (such as BUN (blood urea nitrogen), Cr (creatinine), and GFR (glomerular filtration rate)), urine tests (especially looking for proteinuria), and imaging tests such as CT, MRI, and IVP.
The Best Time to See a Nephrologist
The time it’s best to see a nephrologist can certainly vary depending on your particular conditions. That said, you should ideally be seen by a nephrologist once your creatinine is high enough to be called CKD Stage 4. That would mean a GFR of less than 30.
Importance of Being Referred to a Nephrologist
I am not emphasizing the importance of a referral to a nephrologist because I am one. In fact, multiple medical studies have clearly proved that patients who are referred late to nephrologists are more likely to die, or progress to dialysis!
Risk Factors for Kidney Disease
Since kidney disease can become serious before symptoms are present, it’s important to have a high index of suspicion and be aware of conditions which predispose you to kidney disease. People who are at greater risk of developing renal failure include those with:
Diabetes
Long-standing high blood pressure
Heart diseases such as coronary artery disease, or congestive heart failure
Other vascular diseases such as cerebrovascular disease (strokes) and peripheral vascular disease (such as aortic aneurysms)
A family history of kidney disease
Prolonged use of non-steroidal anti-inflammatory drugs (NSAIDS) such as Advil (ibuprofen) and Celebrex
Treatments
The treatments for kidney disease vary widely based on the particular cause. When kidney function is severely reduced a person may need dialysis for kidney failure or a kidney transplant.
Being Your Own Advocate with Your Kidneys
When it comes to kidney disease, recovery usually does not happen once your GFR has chronically declined to the advanced stages. Hence, the emphasis really needs to be on prevention. The next time you see your physician make sure to discuss the results of your GFR and ask if you should be seen by a specialist.
Bottom Line on When to See a Kidney Doctor
The best time to see a kidney doctor will vary based on your kidney function, the particular renal condition you have, and other risk factors. It appears that a referral to see a nephrologist should be considered for an elevated Cr (stage 4) or a GFR less than 30, but some people should see a kidney doctor much sooner. Since timely consultation with a nephrologist is correlated with survival, it’s best to err on the side of seeing one of these doctors earlier rather than later.
Sources:
Kim, D., Kim, M, Kim, H. et al. Early Referral to a Nephrologist Improved Patient Survival: Prospective Cohort Study for End-Stage Renal Disease in Korea. PLoS One. 2013. 8(1):e55323.
Smart, N., Dieberg, G., Ladhani, M., and T. Titus. Early Referral to Specialist Nephrology Services for Preventing Progression to End-Stage Kidney Disease. Cochrane Database for Systematic Reviews. 2014. (6):CD007333.
Smart, N., and T. Titus. Outcomes of Early versus Late Nephrology Referral in Chronic Kidney Disease: A Systematic Review. American Journal of Medicine. 2011. 124(11):1073-80.e2.
Jun 6, 2018 | News
EARLY TIME-RESTRICTED FEEDING IMPROVES BLOOD SUGAR CONTROL AND BLOOD PRESSURE,S TUDY SHOW
A new pilot study conducted by UAB Department of Nutrition Sciences Assistant Professor Courtney Peterson, Ph.D., shows that eating early in the daytime and fasting for the rest of the day improves blood sugar control, blood pressure and oxidative stress, even when people don’t change what they eat.
“We know intermittent fasting improves metabolism and health,” Peterson said. “However, we didn’t know whether these effects are simply because people ate less and lost weight.”
Peterson and her colleagues decided to conduct the first highly controlled study to determine whether the benefits of intermittent fasting are due solely to eating less. The study was also the first to test a form of intermittent fasting called early time-restricted feeding (eTRF) in humans. eTRF involves combining time-restricted feeding -; a form of intermittent fasting wherein people eat in a 10-hour or shorter period each day -; with eating early in the day to be in alignment with the body’s circadian rhythms in metabolism; it is tantamount to eating dinner in the mid-afternoon and then fasting for the rest of the day.
In the study, eight men with prediabetes tried following eTRF and eating at typical American meal times for five weeks each. On the eTRF schedule, the men each started breakfast between 6:30-8:30 each morning, finished eating six hours later, and then fasted for the rest of the day -; about 18 hours. Everyone finished dinner no later than 3 p.m. By contrast, on the typical American schedule, they ate their meals spread across a 12-hour period. The men ate the exact same foods on each schedule, and the researchers carefully monitored the men to make sure they ate at the correct times and ate only the food that the researchers gave them.
Peterson and colleagues found that eTRF improved insulin sensitivity, which reflects how quickly cells can take up blood sugar, and it also improved their pancreases’ ability to respond to rising blood sugar levels. The researchers also found that eTRF dramatically lowered the men’s blood pressure, as well as their oxidative stress levels and their appetite levels in the evening.
Peterson and colleagues’ research is important because it shows for the first time in humans that the benefits of intermittent fasting are not due solely to eating less; practicing intermittent fasting has intrinsic benefits regardless of what you eat. Also, it shows that eating early in the day may be a particularly beneficial form of intermittent fasting. Peterson hopes the research will also raise awareness of the role of the body’s internal biological clock -; called the circadian system -; in health.
“Our data also indicate that our feeding regimen has to be synchronized with the circadian rhythm and our biological clock,” said Eric Ravussin, Ph.D., director of the Nutrition Obesity Research Center at the Pennington Biomedical Research Center.
Ravussin served as a collaborator with Peterson on the study.
“If you eat late at night, it’s bad for your metabolism,” Peterson said. “Our bodies are optimized to do certain things at certain times of the day, and eating in sync with our circadian rhythms seem to improve our health in multiple ways. For instance, our body’s ability to keep our blood sugar under control is better in the morning than it is in the afternoon and evening, so it makes sense to eat most of our food in the morning and early afternoon.”
Peterson notes that her research sheds light on why intermittent fasting approaches that limit eating to the late afternoon and evening may have failed to find any benefits.
These findings could lead to better ways to help prevent Type 2 diabetes and hypertension. In light of these promising results, Peterson says more research is needed on intermittent fasting and meal timing to find out how they affect health and to figure out what types of approaches are achievable for most people.
Source:
https://www.uab.edu/news/research/item/9433-etrf-improves-blood-sugar-control-and-blood-pressure-pilot-study-says
Jun 6, 2018 | News
NUS RESEARCHERS FIND NOVEL PATHWAY TO REGULATE BLOOD PRESSURE
New and better ways to fight hypertension and low blood pressure may be in the offing, thanks to the National University of Singapore scientists’ discovery of how our blood pressure is controlled.
The finding by the multidisciplinary team from the NUS Yong Loo Lin School of Medicine (NUS Medicine) was published online in the April 2018 issue of Circulation, a leading journal in the cardiovascular field. The team showed that Galectin-1, a protein in our body, influences the function of another protein known as L-type (CaV1.2) calcium channel found in the arteries that normally acts to contract the blood vessels. By reducing the activity of these calcium channels, Galectin-1 is able to lower blood pressure.
This project was led by Professor Soong Tuck Wah from the Department of Physiology together with Dr Hu Zhenyu, the lead author of the study. It takes medical science a step closer toward fighting cardiovascular disorders, which are serious global healthcare issues.
Hypertension – a silent killer
Hypertension is a common problem in Singapore and worldwide. About one in four Singapore residents aged 30 to 69 years have hypertension. Importantly, age is a major risk factor for the development of hypertension. Notably, in the 60 to 69 years age group, more than one in two persons in Singapore have hypertension.
According to the World Health Organization, elevated blood pressure is estimated to cause 7.5 million deaths globally, which represents more than 12 percent of all deaths. This is because hypertension is associated with major killers like coronary heart diseases and stroke. In addition, hypertension can also cause renal impairment, retinal hemorrhage, and visual impairment.
Fighting hypertension – the next wave
As hypertension is a common denominator to many serious conditions described above, nipping the problem at its bud will significantly improve our health.
Although patients with Stage I hypertension are mostly recommended to make lifestyle changes to reduce the risks of suffering other cardiovascular diseases, those with Stage 2 hypertension or above have to take anti-hypertensive medicines to control blood pressure.
Calcium channel blockers (CCB) are traditionally used in the clinics to lower blood pressure, but the use of such medications has been associated with increased risk for heart failure in hypertensive patients, particularly those with heart problems, due to their bad side effects.1 Therefore, the development of drugs that could adjust the activity of the L-type (CaV1.2) calcium channel, rather than blocking its normal function altogether, has emerged as a novel research direction for anti-hypertensive therapeutics. The discovery that Galectin-1 can perform such a desired function represents a pathway to control blood pressure
Galectin-1 reduces the activity of L-type (CaV1.2) calcium channels by blocking their insertion in the cell membrane. The good news is that Galectin-1 only targets this specific type of calcium channel in the blood vessels. It spares other types of calcium channels that are important for the general functions of our body.
“Because Galectin-1 is predominantly found in our blood vessels and because of its selectivity for the Cav1.2 channels, Galectin-1-specific drugs designed to lower our blood pressure are predicted to have minimal side effects,” explained Prof Soong, the lead investigator of the study.
“Currently, calcium channel blockers (CCB) are the most popular class of drugs used to treat high blood pressure because of their good side effect profile and their efficacy. However, many patients are troubled by side effects like leg swelling. Galectin-1-specific drugs have the potential for improved control with fewer side effects,” said A/Prof James Yip, Senior Consultant, Department of Cardiology at the National University Heart Centre, Singapore.
Added Professor Vernon Oh, Department of Medicine, NUS Medicine, “The reported effects of Galectin-1 protein, and of its analogs, on the blood pressure in various models of human arteries and the circulatory system are encouraging. The results suggest that there is a reasonable likelihood of fabricating an antihypertensive treatment-molecule, based on Galectin-1, which will consistently suppress, without negating, the v1.2 calcium channel in human impedance (resistance) arteries, so lowering the blood pressure in persons with pulmonary hypertension. The results from human pulmonary arteries suggest that the candidate treatment-molecule might also be useful in the condition known as pulmonary arterial hypertension, for which highly cost-effective drugs are lacking.” Prof Oh is also a senior consultant at the Division of Advanced Internal Medicine, National University Health System (NUHS).
Conversely, the team also found that interrupting the interaction of Galectin-1 and the L-type calcium channels could raise blood pressure. This finding could lead to new treatments for conditions in which blood pressure is too low, such as sepsis.
Source:
http://nusmedicine.nus.edu.sg/medias/news-info/1810-nus-scientists-discover-a-new-way-to-control-blood-pressure
