Chronic kidney disease – causes, symptoms, diagnosis, treatment, pathology
Chronic kidney disease is a broad term thatincludes subtle decreases in kidney function that develop over a minimum of three months. In contrast, acute kidney injury refers toany deterioration in kidney function that happens in less than three months. Now the kidney’s job is to regulate what’sin the blood, so they might remove waste, or make sure electrolyte levels are steady,or regulate the overall amount of water, and even make hormones – the kidneys do a lotof stuff! Blood gets into the kidney through the renalartery, and once inside it goes gets into tiny clumps of arterioles called glomeruliwhere it’s initially filtered, and the filtrate .
Which is the stuff that gets filtered out,moves into the renal tubule. The rate at which this filtration takes placeis known as glomerular filtration rate or GFR. In a normal healthy person, this is somewherearound 100-120 milliliter of fluid filtered per minute per 1.73 m2 of body surface area. The value is slightly less in women than menand it decreases slowly in all of us as we grow older. One of the most common causes of chronic kidneydisease is hypertension. In hypertension, the walls of arteries supplyingthe kidney begin to thicken in order to withstand .
The pressure, and that results in a narrowlumen. A narrow lumen means less blood and oxygengets delivered to the kidney, resulting in ischemic injury to the nephron’s glomerulus. Immune cells like macrophages and fat-ladenmacrophages called foam cells slip into the damage glomerulus and start secreting growthfactors like Transforming Growth Factor ß1 or TGF-ß1. These growth factors cause the mesangial cellsto regress back to their more immature stem cell state known as mesangioblasts and secreteextracellular structural matrix. This excessive extracellular matrix leadsto glomerulosclerosis, hardening and scarr, .
And diminishes the nephron’s ability tofilter the blood – over time leading to chronic kidney disease. The most common cause of CKD is diabetes,excess glucose in the blood starts sticking to proteins in the blood — a process callednon-enzymatic glycation because no enzymes are involved. This process of glycation particularly affectsthe efferent arteriole and causes it to get stiff and more narrow – a process called hyalinearteriosclerosis. This creates an obstruction that makes itdifficult for blood to leave the glomerulus, and increases pressure within the glomerulusleading to hyperfiltration. .
In response to this high-pressure state, thesupportive mesangial cells secrete more and more structural matrix expanding the sizeof the glomerulus. Over many years, this process of glomerulosclerosis,once again, diminishes the nephron’s ability to filter the blood and leads to chronic kidneydisease. Although diabetes and hypertension are responsiblefor the vast majority of CKD cases, there are other systemic diseases like lupus andrheumatoid arthritis, can also cause glomerulosclerosis. Other causes of chronic kidney disease includeinfections like HIV, as well as long-term use of medications like NSAIDs, and toxinslike the ones in tobacco. Now, normally urea in the body gets excretedin the urine, but when there’s a decreased .
Glomerular filtration fate, less urea getfiltered out, and therefore it accumulates in the blood, a condition called azotemia,which can cause general symptoms like It nausea and a loss of appetite. As the toxin levels really build up, theycan affect the functioning of the central nervous system – causing encephalopathy. This results in asterixis, a tremor of thehand that kind of resembles a bird flapping its wings and is best seen when the personattempts to extend their wrists. Further accumulation of these toxins in thebrain can even progress to coma and death. The buildup of toxins can also cause pericarditiswhich is inflammation of the lining of the .
Heart. In addition, there can be increased tendencyfor bleeding, since excess urea in the blood makes platelets less likely to stick to eachother, and so there’s less clot formation. Finally, in some cases, someone can developuremic frost, where urea crystals can deposit in the skin and they look like powdery snowflakes. In addition to getting rid of waste, the kidneysplay an important role in electrolyte balance. Potassium levels are particularly important,and normally the kidney helps with potassium excretion. In chronic kidney disease, just like withurea, less potassium is excreted and more .
Builds up in the blood, and it leads to hyperkalemia,which is worrisome because it can cause cardiac arrhythmias. Another key role of the kidneys relates tobalancing calcium levels. Normally, the kidney helps to activate vitaminD which helps to increase absorption of calcium from the diet. In chronic kidney disease, there’s lessactivated vitamin D, so less calcium is absorbed into the blood, resulting in hypocalcemia- low calcium levels. As calcium levels in the blood falls, parathyroidhormone is released, causing the bones to lose calcium. .
Over time, this resorption of calcium fromthe bones leaves them weak and brittle, a condition known as renal osteodystrophy. The kidneys also release key hormones. For example, normally when the kidneys startsensing a lower than normal amount of fluid getting filtered, they respond by releasingthe hormone renin to increase the blood pressure. In chronic kidney disease, the falling glomerularfiltration rate leads to more and more renin secretion which leads to hypertension. Now, remember that hypertension is a causeof chronic kidney disease itself, so this creates quite the vicious cycle. .
The kidney also secretes the hormone erythropoietinwhich stimulates the production of red blood cells from the bone marrow. In chronic kidney disease, erythropoietinlevels fall and this leads to lowered production of red blood cells, and ultimately anemia. Ultimately the diagnosis of chronic kidneydisease comes down to looking at changes in the glomerular filtration rate over time. Chronic kidney disease might be suspectedwith a GFR of less than 90 ml/min/1.73 m2 , and irreversible kidney damage might happenwith a GFR below 60 ml/min/1.73 m2. To confirm the diagnosis a kidney biopsy canbe done to look for changes like glomerulosclerosis. .
Treatment for chronic kidney disease ofteninvolves managing the underlying cause. In severe situations, dialysis or a kidneytransplant might be needed. Alright, as a quick recap… chronic kidneydisease is when the glomerular filtration rate falls below 90 ml/min/1.73 m2 over atleast three months. Chronic kidney disease is mainly caused bydiabetes and hypertension, and complications include electrolyte abnormalities, accumulationof toxins in the body, hypertension, and bone abnormalities.