Chapter 65 Renal Failure
Chronic
PATHOPHYSIOLOGY
Chronic renal failure (CRF) is most frequently a result of chronic kidney disease (CKD). The National Kidney Foundation’s Kidney Disease Outcomes Quality Initiative has defined CKD as structural or functional abnormalities that persist for 3 months or longer. Pathologic abnormalities or other markers of kidney damage (abnormal blood or urine tests or imaging studies) are present, with either normal or decreased glomerular filtration rate (GFR). CKD also includes conditions in which the GFR is less than 60 mL/min/1.73 m2 for 3 months or longer. Irreversible deterioration of renal function may occur over months to years.
CKD is classified into five stages. During stage 1, kidney damage is present, with normal or increased glomerular filtration rate (GFR). The focus of stage 1 is on diagnosis, treatment of associated conditions, and slowing the disease process. Stages 2, 3, and 4 represent a progressive decline in GFR. The focus of these stages is on monitoring and treating complications. Preparation for kidney replacement therapy (dialysis) occurs during stage 4. Stage 5 represents renal failure, when the GFR falls below 15 mL/min/1.73 m2. During this stage, the loss of nephrons and renal function affects the kidney’s ability to maintain normal physiologic functioning.
CRF is associated with a variety of biochemical dysfunctions. Sodium and fluid imbalances result from the kidney’s inability to concentrate urine. Hyperkalemia results from decreased potassium secretion. Impaired resorption of bicarbonate and hydrogen ion retention lead to metabolic acidosis. Uremia occurs, with a build-up of blood urea, creatinine, and waste products. Encephalopathy and neuropathy have been associated with the accumulation of uremic toxins. Poor appetite, nausea, and vomiting lead to malnutrition. Anemia results from impaired red blood cell (RBC) production, decreased RBC life span, an increased tendency to bleed (due to impaired platelet function), and poor nutrition. Bone demineralization and impaired growth result from secretion of parathyroid hormone, elevation of plasma phosphate (decreasing serum calcium), acidosis (causing calcium and phosphorus release into the bloodstream), impaired intestinal calcium absorption, and poor nutrition (related to dietary restrictions and other factors). Renal osteodystrophy (altered bone growth) is related to dysfunctional interactions between parathyroid hormone, calcium, phosphorus, and Vitamin D. Growth failure has been associated with growth hormone imbalance and other nutritional and metabolic factors. Altered sexual development has been associated with a variety of biochemical processes.
Causes of CRF are associated with a variety of congenital and acquired factors including the following:
1. Glomerular disease (e.g., pyelonephritis, glomerulonephritis, glomerulouropathy)
2. Obstructive uropathies (e.g., vesicoureteral reflux)
3. Renal hypoplasia or dysplasia
4. Inherited renal disorders (e.g., polycystic kidney disease, congenital nephrotic syndrome, Alport syndrome)
5. Vascular neuropathies (e.g., hemolytic-uremic syndrome [HUS], renal thrombosis)
6. Kidney loss or damage (e.g., severe renal trauma, Wilms’ tumor)
INCIDENCE
1. The incidence of CRF in children has been increasing for many years. It is expected to rise in the future along with the increasing incidence of diabetes, hypertension, and obesity in the United States.
2. The exact incidence of CRF in children is difficult to quantify. It has been estimated at approximately 1:100,000. Incidence is highest in adolescents and males.
3. The most frequent causes (nearly 50%) of CRF in young children are related to congenital renal and urinary tract malformations (e.g., renal hypoplasia, renal dysplasia, obstructive uropathies, vesicoureteral reflux). Acute renal diseases such as glomerulonephritis, HUS, and pyelonephritis are the most frequent causes of acquired CRF in older children.
CLINICAL MANIFESTATIONS
Although the child’s symptoms will vary with different disease processes, the most common symptoms associated with CRF are the following:
1. Fluid and electrolyte imbalance, leading to the following:
2. Metabolic acidosis causing tachypnea and/or decreased serum bicarbonate
4. Anemia, resulting in the following:
5. Uremic neurologic effects (neuropathy and encephalopathy), leading to the following:
6. Renal osteodystrophy leading to the following:
7. Growth and development dysfunction leading to the following:
COMPLICATIONS
1. Cardiovascular: alteration in fluid and electrolytes, acid-base imbalance (metabolic acidosis), and anemia can lead to cardiac dysfunction, congestive heart failure, hypertension, left-ventricular hypertrophy, tachycardia, arrhythmias, cardiac arrest, and/or vascular volume depletion (with excessive fluid loss or removal). Fluid overload can lead to edema, oliguria, hypertension, and/or congestive heart failure. Conversely, polyuria, decreased fluid intake, and other factors causing vascular volume depletion can lead to dehydration, hypotension, and shock.
2. Electrolyte imbalances: hyperkalemia can lead to cardiac rhythm disturbances and myocardial dysfunction. Hypernatremia can lead to thirst, stupor, tachycardia, increased deep tendon reflexes, and/or decreased level of consciousness. Hypercalcemia and/or hyperphosphatemia can lead to muscle cramps, tetany, paresthesias, irritability, depression, and/or psychosis.
3. Respiratory: fluid overload can lead to pulmonary edema, increased work of breathing, and respiratory failure. Shortness of breath and exercise intolerance related to anemia can exacerbate respiratory compromise.
4. Neurologic: altered level of consciousness, increased ICP, seizures, and coma can result from the build-up of toxins, fluid and electrolyte imbalance, and other metabolic factors.
5. Hematologic: bleeding and/or anemia—bruising, mouth sores, gastrointestinal bleeding, oozing from puncture sites, and other bleeding can occur related to hematologic dysfunction and/or prolonged bleeding time.
6. Infection: increased susceptibility, decreased ability to fight infection, and invasion of opportunistic organisms is related to invasive lines and procedures, skin breakdown, poor nutrition, and the need to administer antibiotics with caution (related to the kidneys’ limited ability to metabolize and excrete).
7. Alteration in growth and bone: altered growth patterns, short stature, osseous deformities, dental defects, and mouth sores are related to poor nutrition, osteodystrophy, and/or other factors affecting bone growth and formation.
