Content Reviewers:Antonella Melani, MD, Lisa Miklush, PhD, RNC, CNS, Ashley Mauldin MSN, APRN, FNP-BC, Gabrielle Proper, RN, BScN, MN
Chronic kidney disease, or CKD for short, is a condition characterized by a slow and progressive decrease in kidney function, with a glomerular filtration rate, or GFR, of less than 60 mL/minute that develops over a minimum of three months.
Now, let’s take a closer look at how the kidneys work. We can think of the kidneys as the body’s natural blood filter. Their main function is to clear blood of metabolic wasteful substances and toxins by excreting them through urine. In addition, they secrete important hormones, and are essential in regulating the acid-base balance, pH, blood pressure, and electrolyte levels in the body.
Within each kidney, there are millions of tiny functional units called nephrons, which consist of a renal corpuscle and a set of renal tubules. The renal corpuscle is where blood filtration occurs, and it includes the glomerulus, a tiny bundle of capillaries, and the Bowman’s capsule, a cup-shaped structure that surrounds the glomerulus.
As blood flows through the glomerulus, water and small solutes dissolved in the blood are filtered into the Bowman’s capsule, creating an ultrafiltrate of blood. This filtrate then travels through the renal tubules, where urine is ultimately produced and modified according to the body’s necessities. The rate at which renal filtration takes place is called glomerular filtration rate, or GFR for short, and it is one of the main measures of kidney function. In a healthy adult, the estimated GFR is around 100-120 mL/min, and this value decreases slowly in all of us as we grow older.
All right, now, several conditions can speed up the rate at which GFR deteriorates, increasing the risk of developing CKD. In the United States, the leading causes of CKD are diabetes mellitus and hypertension, both of which are more common in elderly clients. Less common causes include renal artery stenosis, glomerular diseases, polycystic renal disease, tubulointerstitial diseases, and systemic disorders, like lupus or amyloidosis. Additionally, repeated episodes of pyelonephritis or obstructive uropathy, such as prostate disease, can also lead to CKD.
Regarding risk factors for CKD, modifiable ones include obesity, cardiovascular disease, uncontrolled diabetes mellitus, smoking, and exposure to nephrotoxic medications like NSAIDs or aminoglycosides; while nonmodifiable risk factors include being over 60 years of age and having a genetic predisposition to kidney disease.
Now, regardless of its cause, CKD results from progressive and irreversible damage to the kidneys, leading to a gradual decline in kidney function. As a result, the kidneys gradually lose their ability to concentrate the urine and excrete wasteful substances or toxins. So, CKD can be classified into five stages by determining the estimated GFR, which is measured in units of milliliters per minute per 1.73 square meters.
In clients at stage 1 CKD, there’s still a normal kidney function, since the remaining healthy nephrons are able to adapt, become larger, and work harder to maintain urine production. As the disease progresses into stage 2 CKD, kidney function is mildly decreased; while in stage 3 CKD, there’s a moderate decrease, and in stage 4 CKD, there’s a severe decrease in kidney function. Over time, as CKD progresses into stage 5, kidney function is completely lost, and clients develop renal failure, also known as end-stage kidney disease, or ESRD for short.
Now, the body is capable of coping with a significant reduction in kidney function without causing any symptoms, which makes CKD a largely silent disease. As the kidneys lose their ability to concentrate urine, clients may experience polyuria and nocturia. As damage progresses, though, fluid retention is more common and may result in edema and oliguria. In addition, as urine output decreases, wasteful substances or toxins like urea and creatinine begin to accumulate in the body; this can lead to uremia, which may cause general symptoms like fatigue, nausea, and loss of appetite.
As toxin levels build up, they can affect the functioning of the nervous system, resulting in uremic encephalopathy. This can cause asterixis, a tremor of the hand that appears when a client attempts to extend their wrists, along with ataxia and lethargy. The buildup of toxins can also affect the heart causing pericarditis. In some cases, clients can develop uremic frost, where urea crystals deposit in the skin giving the appearance of powdery snowflakes.
Additionally, clients with CKD often have hypertension due to sodium retention and activation of the renin-angiotensin system. Finally, clients may develop blood abnormalities, such as anemia, hyperkalemia, metabolic acidosis, and disorders of phosphate and calcium metabolism. Over time, resorption of calcium from the bones in an attempt to restore blood calcium levels can leave bones weak and brittle, which is known as renal osteodystrophy.
Ultimately, diagnosis of CKD is based on laboratory tests. These include blood tests showing an increase in blood creatinine, BUN, as well as a decrease in an estimated GFR. A urinalysis will show proteinuria, hematuria, white blood cells, glucose, and casts. If the exact cause of CKD is unknown, an abdominal ultrasound can be done to look for signs of scarring or polycystic kidneys, as well as obstructive uropathy. In long-term ESRD, X-rays may be done to check for renal osteodystrophy. Finally, a kidney biopsy can be done to look for inflammation, scarring or unusual deposits of a protein, and to determine how far CKD has advanced.
The goal of the treatment in CKD depends on the stage. In clients at stages 1 and 2, the main goal is making sure the client has an adequate fluid balance, as well as slowing down the decline in kidney function and preventing complications. This involves lifestyle modifications like smoking cessation, stopping any nephrotoxic medications, and maintaining a tight blood glucose control among clients with diabetes mellitus. Two of the main factors involved in the progression of CKD are hypertension and proteinuria, so clients often require treatment with an ACE inhibitor like enalapril or an ARB like losartan. Clients with hyperlipidemia should be started on lipid lowering agents to reduce cardiovascular risk.
On the other hand, in clients with stage 3 CKD, all blood abnormalities like anemia and electrolyte imbalances should be corrected as needed. If there’s evidence of renal osteodystrophy, additional measures, like calcium supplementation or treatment with phosphate binders, should be taken to prevent further loss of bone density. When clients reach stage 4, kidney function is severely reduced, so treatment involves getting them prepared for renal replacement therapy options, which include hemodialysis, peritoneal dialysis, and renal transplantation. Finally, in stage 5 CKD, the remaining kidney function is not enough to maintain life, so clients should be started on renal replacement therapy and consider kidney transplantation.
Now, let’s look at the nursing care of a client with chronic kidney disease. Keep in mind that nursing care may vary based on the progression and stage of kidney dysfunction that your client is experiencing. The overall goals are to maintain fluid and electrolyte balance, slow the progression of the disease, and manage any disease complications.