Chronic Kidney Disease

Chronic kidney disease is a progressive deterioration of kidney function. Slowly and gradually, and over a long period of time, increasing numbers of nephrons become damaged. Damaged nephrons are unable to perform their usual task of filtration.

However, many years can go by before there are any symptoms. This is because the kidneys are able to compensate remarkably. Even with a substantial number of damaged nephrons, the kidney is able to maintain its functions. It does this by increasing the filtration rate of the healthy nephrons.

After many years however, as the number of damaged nephrons continues to increase, eventually the remaining functioning nephrons are unable to compensate adequately. Filtration becomes inadequate, causing waste products to accumulate in the blood, and causing many complications to arise.

Causes
There are many causes of chronic kidney disease, but the most common are:

  • Untreated hypertension – high pressures cause damage to the delicate nephrons
  • Untreated diabetes – high blood glucose causes damage to the delicate nephrons

Signs and Symptoms
Chronic kidney disease is usually an asymptomatic disease, until it is in its advanced stages. Usually many years go by without the patient experiencing any symptoms. By the time symptoms present, the patient usually has very advanced disease

Symptoms of advanced kidney disease may include fatigue, appetite loss, nausea and vomiting, pruritus, and nocturia. Some patients can also develop yellow skin. 

Complications
Advanced chronic kidney disease can cause many complications, including:

  • Volume overload – the damaged nephrons are not able to filter adequately, leading to retention of salt and water.
  • Hypertension – volume overload requires the heart to contract with greater force, which raises the blood pressure.
  • Electrolyte abnormalities – the damaged nephrons are not able to filter the electrolytes adequately, leading to deranged levels of electrolytes in the blood.
  • Impaired immunity – the immune system does not function as well as it should, which increases the patient’s susceptibility to infection
  • Anemia – the diseased kidney decreases it production of erythropoietin (a hormone that stimulates production of red blood cells in the bone marrow), causing a decrease in the number of red blood cells in the body.

Investigations
An analysis of the urine should be performed, especially to examine for protein in the urine (proteinuria). Protein is a valuable nutrient that the kidney normally preserves, but in advanced kidney disease it will be excreted into the urine.

Blood tests for kidney function (creatinine and urea) should be performed. Creatinine and urea are waste products that the nephrons usually filter out of the blood. In advanced kidney disease these waste products are not filtered out adequately. Therefore, the levels of creatinine and urea increase in the blood.

Blood tests also include checking the electrolyte levels, especially the potassium level.

The hemoglobin level should also be checked. This is because anemia is a common complication of chronic kidney disease.

A blood test called the glomerular filtration rate (GFR) reveals the amount of fluid filtered by the glomeruli each minute. Results that are low are suggestive of nephrons that are damaged and not filtering adequately. 

An electrocardiogram (ECG) can be performed to assess for conduction abnormalities associated with high potassium levels (hyperkalemia).

Some patients may need further investigations if the cause of the kidney disease is not identified. This may include renal ultrasound and urine microscopy. On rare occasions biopsy may be required.

Treatment
Advanced chronic kidney disease cannot be reversed, but treatment can help to slow the progression. Progression is slowed by treating the underlying cause, for example treating diabetes or hypertension.

The complications of chronic kidney disease also need to be treated when they present, such as:

  • Volume overload – volume overload is treated with diuretics (such as furosemide), together with a fluid restriction. A dietary salt restriction is also advised.
  • Hypertension – treatment of chronic hypertension is important, as hypertension causes acceleration of chronic kidney disease. Daily antihypertensive medications may be required.
  • Electrolyte abnormalities – electrolyte abnormalities may need to be corrected. The potassium level is of particular importance in kidney disease, as high potassium levels (hyperkalemia) can cause life threatening cardiac arrhythmias.
  • Impaired immunity – infections should always be searched for and treated. Extra infection control precautions are also necessary.
  • Anemia – subcutaneous erythropoietin injections can be given. Iron supplementation can also be given. Blood transfusion may also be required for severe anemia.

If the complications of kidney disease are severe and not responding to treatment, then dialysis may be required. Indications for dialysis include any of the following: dangerously high potassium levels (hyperkalemia), severe pulmonary oedema, severe metabolic acidosis, very high levels of urea (uremia). Because chronic kidney disease is a chronic disease, therefore dialysis may be required regularly and indefinitely.