STEUP Renal and Genitourinary System: Proteinuria and Hematuria Flashcards
What is proteinuria defined as?
Urinary excretion of >150mg protein/24 hours
What are the classifications of proteinuria causes?
1) Glomerular
2) Tubular
3) Overflow proteinuria
4) Other causes of proteinuria (all of the following can affect renal blood flow)
a) UTI
b) Fever, heavy exertion/stress, CHF
c) Pregnancy
d) Orthostatic proteinuria - occurs when the patient is standing but not when recumbent; self-limited and benign
What is glomerular proteinuria due to? What can it lead to? When can it be seen? Is it severe?
1) Due to increased glomerular permeability to proteins
2) Can lead to nephrotic syndrome
3) May be seen in all types of GN
4) Protein loss tends to be more severe than in nonglomerular causes
What happens in tubular proteinuria? Is it severe? What are causes?
1) Small proteins normally filtered at the glomerulus then reabsorbed by the tubules appear in the urine because of abnormal tubules (i.e., due to decreased tubular reabsorption)
2) Proteinuria tends to be less severe
3) Causes include sickle cell disease, urinary tract obstruction, and interstitial nephritis
What is overflow proteinuria?
Increased production of small proteins overwhelms the tubules’ ability to reabsorb them (e.g., Bence Jones protein in multiple myeloma)
What are the key features of nephrotic syndrome?
1) Urine protein excretion rate > 3.5g/24 hours
2) Hypoalbuminemia
3) Edema
4) Hyperlipidemia and lipiduria
5) Hypercoagulable state
6) Increased incidence of infection
Why do you get hypoalbuminemia in nephrotic syndrome?
Hepatic albumin synthesis cannot keep up with these urinary protein losses. The result in decreased plasma oncotic pressure, which leads to edema
Why do you get edema in nephrotic syndrome?
This is often the initial complaint (from pedal edema to periorbital to anasarca, ascites, pleural effusion), and results from hypoalbuminemia. Increased aldosterone secretion exacerbates the problem (increases sodium reabsorption)
Why do you get hyperlipidemia and lipiduria in nephrotic syndrome?
Increased hepatic synthesis of LDL and VLDL because liver is revving up albumin synthesis
Why do you get a hypercoagulable state in nephrotic syndrome? What is the patient at increased risk for?
1) Hypercoagulable state due to loss of certain anticoagulants in the urine
2) Increased risk of thromboembolic events (deep venous thrombosis, pulmonary embolism, renal vein thrombosis)
Why do you get an increased incidence of infection in nephrotic syndrome?
Results from loss of immunoglobulins in the urine
What kind of disease does nephrotic syndrome usually indicate? What is the underlying cause of nephrotic syndrome?
1) Significant glomerular disease (either primary or secondary to systemic illness)
2) The underlying cause is abnormal glomerular permeability
What are different types of causes of nephrotic syndrome?
1) Primary glomerular disease (50% to 75% of cases of nephrotic syndrome)
2) Systemic disease
3) Amyloidosis, cryoglobulinemia
4) Drugs/toxins
5) Infection
6) Multiple myeloma, malignant HTN, transplant rejection
What are the primary glomerular diseases that cause nephrotic syndrome?
1) Membranous nephropathy is most common in adults (40% of cases)
2) Focal segmental glomerulosclerosis (FSGS) (35%)
3) Membranoproliferative GN (15%)
4) Minimal change disease (MCD) is the most common cause in children (75% of cases)
What are the systemic diseases that cause nephrotic syndrome?
1) Diabetes
2) Collagen vascular disease
3) SLE
4) RA
5) Henoch-Schonlein purpura
6) Polyarteritis nodosa (PAN)
7) Wegener granulomatosis
What are the drugs/toxins that cause nephrotic syndrome?
1) Captopril
2) Heroin
3) Heavy metals
4) NSAIDs
5) Penicillamine
What are the three classes of infections that cause nephrotic syndrome?
1) Bacterial
2) Viral
3) Protozoal
What is the first test that can be done in diagnosis of nephrotic syndrome? What is it specific for? How is it graded? What is a disadvantage of the test that can lead to false-negative results?
1) Urine dipstick test (read color changes)
2) Specific for albumin - detects concentrations of 30 mg/dL or higher
3) Graded 0, trace, 1+ (15 to 30 mg/dL) through 4+ (>500 mg/dL)
4) More sensitive to albumin than to immunoglobulins, thus can lead to false-negative results when predominant urinary protein is globulin (e.g., light chains in myeloma)