CHAPTER 16 Kidney Disorders
I. Background
A. The kidneys are responsible for removing toxins, chemicals, and waste products from the blood; regulating acid concentration; and maintaining water and electrolyte balance in the body by excreting urine.
Table 16-1 National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI™) Staging System for Chronic Kidney Disease
| Stage | Description | Glomerular Filtration Rate (GFR) (mL/min/1.73 m2) |
|---|---|---|
| 1 | Kidney damage with normal or increased GFR | ≥90 |
| 2 | Kidney damage with a mild decrease in GFR | 60–89 |
| 3 | Moderate decrease in GFR | 30–59 |
| 4 | Severe decrease in GFR | 15–29 |
| 5 | Kidney failure | <15 (or dialysis) |
Reprinted from American Journal of Kidney Diseases, 39(2):35, 2002, with permission from Elsevier.
II. Common Types and Causes of Kidney Disorders
A. Fanconi syndrome
1. Definition: The tubes in the kidneys do not work properly.
a) Unable to reabsorb glucose, amino acids, small proteins, water, calcium, potassium, magnesium, bicarbonate, and phosphate, making the blood overly acidic
b) May be caused by inherited disorders such as cystinosis, galactosemia, glycogen storage disease, hereditary fructose intolerance, Lowe syndrome, Wilson’s disease, tyrosinemia, medullary cystic disease, and vitamin D dependency; exposure to heavy metals, certain drugs, chemicals (e.g., toluene), or dietary supplements (e.g., lysine); and may even result from kidney transplantation
B. Glomerulonephritis
1. Definition: an acute or chronic kidney disease that occurs when the kidneys are unable to properly remove waste and excess fluids from the body. This occurs when there is glomerular damage from immune or inflammatory reactions and lesions.
2. It can occur by itself or in conjunction with other diseases such as lupus, Goodpasture syndrome, diabetes, immunoglobulin A (IgA) nephropathy, polyarteritis, Wegener granulomatosis, or infection with streptococcus, HIV, hepatitis B or C
3. Signs and symptoms: dark-colored urine, foamy urine, high blood pressure, fluid retention that causes swelling, fatigue, and less-frequent urination
4. Treatment
a) The goal of treatment is to reduce the decline of kidney function and control blood pressure. Corticosteroids are often used to reduce kidney inflammation. Diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor agonists (ARB), calcium channel blockers, or beta blockers may be used.
C. Focal segmental glomerulosclerosis (FSGS)
1. Definition: A type of glomerular disease that can cause permanent kidney disease in children and adults by attacking the glomeruli, the tiny structures inside the kidneys where blood is filtered. The most common sign of FSGS is the nephrotic syndrome, which is characterized by fluid in the body tissues that causes swelling, excess protein in the urine, hypoalbuminemia, and high cholesterol.
2. Signs and symptoms
b) Patients develop nephrotic syndrome, which is characterized by fluid retention that causes swelling and weight gain of 15 to 20 pounds or more, foamy urine, abnormally low levels of albumin in the blood, hypertension, and high cholesterol. Fluid in the lung cavity, abdomen, and in the sac that surrounds the heart may build-up and fill the cavities.
D. Kidney stones: Kidney stones (also called renal calculi, urinary calculi, urolithiasis, or nephrolithiasis) usually develop when the urine becomes too concentrated. As a result, minerals and other substances in the urine form hard crystals on the inner surfaces of the kidneys. Over time, these crystals may combine to form a small, hard mass, or stone.
1. Calcium stones are the most common type of kidney stones, accounting for 80% of cases. Calcium stones develop when there are high levels of calcium (hypercalcemia) and oxalate in the blood.
2. Struvite stones are usually caused by chronic urinary tract infections. The bacteria that cause these infections release enzymes that increase the amount of ammonia in the urine. This excess ammonia may form large, sharp stones that can potentially damage the kidneys.
3. Cystine stones develop in patients who have an inherited disorder called cystinuria. This disorder causes the kidneys to release too many amino acids, which then form stones.
4. Signs and symptoms
a) Patients may experience intense pain that comes and goes, lasting 5 to 15 minutes at a time. Pain usually begins in the lower back and moves to the abdomen, groin, or genital areas as the stone moves from the kidney toward the bladder. Other symptoms include blood in the urine, cloudy or foul-smelling urine, nausea, vomiting, and constant urge to urinate
5. Treatment
a) Calcium stones: Thiazide diuretics lower urine calcium in idiopathic hypercalciuria and are effective in preventing the formation of stones.
b) Uric acid stones: The two goals of treatment are to raise urine pH and to lower excessive urine uric acid excretion to less than 1 g per day. Supplemental alkali, 1–3 mmol/kg of body weight per day, should be given in three or four evenly spaced, divided doses, one of which should be given at bedtime.
c) Cystine stones: high fluid intake, even at night. Daily urine volume should exceed 3 L. Raising urine pH with alkali is helpful, provided the urine pH exceeds 7.5.
d) Struvite stones: Complete removal of the stone and subsequent sterilization of the urinary tract is the treatment of choice for patients who can tolerate the procedures. Irrigation of the renal pelvis and calyces with hemiacidrin, a solution that dissolves struvite. For patients who are not candidates for surgery, acetohydroxamic acid, and inhibitor of urease, can be used.
E. Nephrotoxicity
1. Definition: A term used to describe toxic damage in the kidneys; electrolytes in the blood, including potassium and magnesium, build up to toxic levels.
F. Diabetic nephropathy
1. Kidney disease that develops as a result of diabetes mellitus (DM); most common cause of kidney failure in the United States, accounts for more than one third of all patients who are on dialysis
2. Approximately 25% to 40% of patients with DM type 1 ultimately develop diabetic nephropathy (DN), which progresses through five predictable stages.
b) Stage 2 (developing diabetes): GFR remains elevated or has returned to normal, but glomerular damage has progressed to significant microalbuminuria (small but above-normal level of the protein albumin in the urine).
c) Stage 3 (overt, or dipstick-positive diabetes): Glomerular damage has progressed to clinical albuminuria.
d) Stage 4 (late-stage diabetes): Glomerular damage continues, with increasing amounts of protein albumin in the urine. The kidneys’ filtering ability has begun to decline steadily, and blood urea nitrogen (BUN) and serum creatinine (SCr) has begun to increase. The GFR decreases approximately 10% annually. Almost all patients have hypertension at stage 4.
G. Nephrotic syndrome
1. Nephrotic syndrome is a disorder of the glomeruli (clusters of microscopic blood vessels in the kidneys that have small pores through which blood is filtered) in which excessive amounts of protein are excreted in the urine (proteinuria). This typically leads to accumulation of fluid in the body (edema), low levels of the protein albumin (hypoalbuminemia), and high levels of fats (hyperlipidemia) in the blood.
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