What is Chronic Kidney Disease?

Chronic Kidney Disease (CKD) is an alteration in the normal function of the kidneys caused by a chronic process and it is usually not reversible. Functionally, the kidney tissue is less capable of performing its functions which include: the filtration of blood, the control of the acid base status, electrolyte concentration control, fluid and blood pressure management, generation of erythropoietin for red blood cell production and  activation of vitamin D.

The processes that most commonly result in CKD are persistent uncontrolled hyperglycemia from diabetes mellitus, persistently elevated blood pressures, acute or subacute inflammatory conditions of the kidneys and genetically mediated anatomic abnormalities such as polycystic kidney disease (PKD). These processes result in scarring and fibrosis of the kidney tissue, with loss of renal cells in the cortex and medullary portions of the kidneys. 

Chronic kidney disease is usually classified in stages, going from I to V. The function that has been chosen to  assign the stages is the filtration function, measured as a variable called glomerular filtration rate (GFR). Although the kidney has many different functions, they are related to each other. The relationship is not perfect, but is is safe to say that if there is a reduction on the filtration function function of the kidneys, the other functions will be affected, in variable degrees. It is also possible that certain functions of the kidney may be affected with little change in other functions, for example, there are conditions that involve abnormalities in the handling of potassium or acidity without a change in the filtration function or generation of erythropoietin, however, these conditions are not too common.

The final stage of CKD is called end-stage renal disease (ESRD). At this stage, renal replacement therapy (RRT) becomes necessary. RRT includes dialysis (in its different modalities) and renal transplantation.

Marco A. Ramos MD

Vitamin D and Cancer

In a previous post from January 27, 2016  (http://blog1.smopinions.com/2016/01/7-interesting-facts-about-vitamin-d.html), it was mentioned that there are associations between vitamin D deficiency and certain types of cancer. This post will explain a little bit more about them.

Regarding colorectal cancer, it was noticed about 2 decades ago, that there is more mortality from colorectal cancer in the northern and northeastern parts of the United States, the ones which receive less sunlight. This in itself is not enough to establish a meaningful association, however, it gave a starting point for research. Then, 2 studies showed that having levels above 30 ng/dL in the blood may reduce the incidence of colorectal cancer by half^1,2.

With respect to breast cancer, a recent study found that postmenopausal women may get a benefit from having adequate vitamin D levels in the blood. The risk of developing breast cancer in this particular group of women was lower than in the same group of women with lower vitamin D in their blood³.

Finally, in regards to prostate cancer, it has been found that this cancer is also more common in regions with less sun exposure. In addition, lower vitamin D levels in the blood are related to more aggressive forms of prostate cancer. Last but not least, adequate levels of vitamin D may aid in the slowing of the progression of this type of cancer⁴.

More research is needed in order to confirm and strengthen these associations. In the mean time, it does not hurt to have adequate levels of vitamin D in the blood, particularly for people living north of the 30th parallel.

References

1. Serum 25-hydroxyvitamin D and colon cancer: eight-year prospective study. Garland CF, Comstock GW, Garland FC, Helsing KJ, Shaw EK, Gorham ED. Lancet. 1989;2(8673):1176-8.

2. Meta-analysis: longitudinal studies of serum vitamin D and colorectal cancer risk. Yin L, Grandi N, Raum E, Haug U, Arndt V, Brenner H. Alim Pharm Therap. 2009 30(2):113-25

3. Plasma vitamin D levels, menopause, and risk of breast cancer: dose-response meta-analysis of prospective studies. Bauer SR, Hankinson SE, Bertone-Johnson ER, Ding EL. Medicine (Baltimore). 2013;92(3):123-31

4. Association between serum 25(OH)D and death from prostate cancer. Tretli S, Hernes E, Berg JP, Hestvik UE, Robsahm TE. Br. J. Cancer 2009;100(3):450-4.

Marco A. Ramos MD

5 Possible Consequences of Uncontrolled High Blood Pressure

Uncontrolled high blood pressure (hypertension) is associated with several health conditions. Hypertension is treatable, so this means that the following diseases can be prevented or delayed. 

1. Heart attacks. Elevated blood pressure is related to atherosclerosis, which, by narrowing the coronary arteries, can lead to heart attacks. Heart attacks can cause congestive heart failure and sudden death. 

2. Impaired vision. Hypertension can cause something called hypertensive retinopathy. This means that the retina (where the images are formed in the eye) can get damaged by chronic high blood pressure and can lead to impaired vision and blindness.

3. Amputation of limbs. High blood pressure can lead to the amputations of limbs, specially feet and legs. The problem starts with the atherosclerosis in the arteries of the limbs which eventually leads to obstruction and lack of blood supply to the feet and legs, especially. Hypertension is related to the atherosclerosis of the limb arteries, just as with the heart.

4. Stroke. The brain can also be the victim of atherosclerosis, which is related with hypertension (as we have just seen). In addition to this, if the blood pressure becomes too high, it can lead to bleeding inside the brain, by rupture of the arteries.

5. Kidney disease. The kidneys are very sensitive. Elevated blood pressure for a long time can cause scarring of the kidney tissue to the point that it cannot perform its functions anymore. The kidneys are important for sodium and potassium control, blood pressure control, generation of red blood cells, vitamin D and calcium metabolism and acid-base balance.

Marco A. Ramos MD

7 Interesting Facts About Vitamin D That You Were Probably Not Aware Of

1. Vitamin D is not a vitamin. It is a hormone. it is structurally related to steroids and has intracellular receptors. It does not function as a cofactor in biochemical reactions like vitamins¹.

2. There is a link between vitamin D deficiency and seasonal affective disorder (SAD), a form of depression which happens more often in winter months². 

3. Vitamin D is produced in the the skin (from the interaction with sunlight) and undergoes 2 modifications, one in the liver and another one in the kidney in order to achieve its full effects.

4. There are receptors for vitamin D, almost in every cellular type of the body. Intestines, bones, brain, kidneys are just examples of organs where vitamin D has an effect.

5. Darker skinned people are more vitamin D deficient than lighter skin people. Also, people living north (or south) of the 30th parallel are more deficient than those who do not.

6. There are significant associations between vitamin D deficiency and cancer, specially colorectal, breast and prostate cancers^3,4,5.

7. There is an association between all-cause mortality and low levels of vitamin D⁶.

References

1. Vitamin D: A Hormone for All Seasons - How much is enough? Understanding the New Pressures. Morris H. The Clinical Biochemist Review. 2005; 26(1): 21–32.

2. Association Between Low Serum 25-Hydroxyvitamin D and Depression in a Large Sample of Healthy Adults: The Cooper Center Longitudinal Study. Hoang, MinhTu T. et al. Mayo Clinic Proceedings. 2011;86(11): 1050-1055

3. Association between vitamin D and risk of colorectal cancer: a systematic review of prospective studies. Ma Y, Zhang P, Wang F, et al. Journal of Clinical Oncology. 2011;29(28): 3775-3782.

4. Vitamin D Deficiency Predicts Prostate Biopsy Outcomes. Murphy AB. Clinical Cancer Research. 2014;20(9): 2289–2299.

5. Vitamin D and Reduced Risk of Breast Cancer: A Population-Based Case-Control Study. Knight JA et al. Cancer Epidemiology Biomarkers Prevention. 2007;16(3):422–429

6. Meta-analysis of All-Cause Mortality According to Serum 25-Hydroxyvitamin D. Garland CF et al. American Journal of Public Health. 2014;104(8): e43-e50.

Marco A. Ramos MD

The Many Functions of the Kidney

The kidney has many vital functions. They can be altered by disease, trauma, medications or intoxications. Although the kidney is widely recognized as the organ which “makes urine” and in the process “cleaning the body from unnecessary substances”, it has many other functions.

The kidney regulates the level of fluid the body has. This function is closely tied with the regulation of the sodium and water contents of the body and with the blood pressure control. If this property fails, the could be high blood pressure, low blood pressure, high sodium or low sodium levels in the blood.

The body is alive because it can keep a tightly regulated pH (or acid-base status). If the blood pH drops below 6.8 or goes higher than 7.6 life is not sustainable. The kidney (together with the lung) is key in the control of the blood acid-base status.

The body needs a sensor to be able to create more red blood cells when they are needed. This sensor is the kidney. There is a hormone called erythropoietin which is secreted when there are less red blood cells or when the blood carries less oxygen.

The bone metabolism needs the kidney to produce activated vitamin D. This hormone is essential for the absorption of calcium from the intestine and to suppress another hormone called PTH, which if not suppressed it can lead to loss of bone mass and loss of phosphorus though the urine.

The body needs to keep a tight control of the potassium concentration in the extracellular fluid. The kidney is in charge to determine how much potassium should be allowed in the urine and how much should be retained.

The kidney has to be able to filtrate certain substances and to keep others. If the kidney were to let all substances be filtered, we would lose important proteins such as albumin and immunoglobulins (antibodies) though the urine.

By doing this quick summary, it is obvious that the kidney is a complex organ. The available forms of dialysis do a good job trying to mimic the function of the kidney, however, they are far away from perfect. The proof of this is how much better the results of kidney transplantation are compared to the results of dialysis.

Marco A. Ramos MD