In chronic kidney disease (CKD), the presence of proteinuria is primarily attributed to:
Glomerular hyperfiltration and increased glomerular capillary permeability
Decreased filtration of proteins in the renal tubules
Impaired reabsorption of proteins in the renal tubules
Increased glomerular filtration rate (GFR)
The Correct Answer is A
A. Proteinuria occurs because damaged glomerular basement membranes and podocytes lose their size-selective and charge-selective properties, allowing large proteins like albumin to leak into the filtrate. Additionally, the remaining healthy nephrons undergo compensatory hyperfiltration, which increases the pressure and movement of proteins across the capillary wall. This persistent leakage is both a marker and a driver of renal progression.
B. Proteins are not "filtered" in the sense of being waste products; they are supposed to be retained within the vascular compartment by the glomerular barrier. The term "decreased filtration" would imply that proteins are staying in the blood, which would actually prevent proteinuria. The pathology of CKD involves a failure to exclude these macromolecules from the urinary space.
C. While some small proteins are normally filtered and then reabsorbed in the proximal tubule, this mechanism is overwhelmed by the massive influx of protein from the glomerulus. Impaired tubular reabsorption can cause mild proteinuria, but the hallmark "nephrotic" or "macro" levels of protein in CKD are due to glomerular breach. The primary defect lies in the filtration barrier rather than the recovery system.
D. Chronic kidney disease is fundamentally defined by a decreased glomerular filtration rate, not an increased one. Although individual surviving nephrons may hyperfilter, the total GFR of the entire kidney is significantly reduced as more functional units are lost. An overall increased GFR would be a sign of hyperperfusion, which is not the defining characteristic of advancing kidney failure.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Direct damage to the renal parenchyma is the defining characteristic of intrinsic renal failure, such as acute tubular necrosis or glomerulonephritis. This involves structural injury to the functional components of the kidney itself. Postrenal failure is defined by factors external to and downstream from the renal tissue and architecture.
B. Obstruction of the urinary tract is the primary pathophysiological mechanism of postrenal failure, which occurs when urine flow is blocked. This blockage increases retrograde hydrostatic pressure within the Bowman capsule, eventually opposing glomerular filtration. Common causes include nephrolithiasis, prostatic hyperplasia, or tumors that impede the elimination of urine.
C. Inflammation and infection of the renal tubules, such as in acute interstitial nephritis or pyelonephritis, are causes of intrinsic renal injury. These processes involve an immune or infectious assault on the internal renal structures. Postrenal failure specifically refers to mechanical or functional obstruction occurring after the urine has left the parenchyma.
D. Inadequate blood flow to the kidneys is the hallmark of prerenal failure, where the kidneys are structurally intact but under-perfused. This typically results from systemic hypotension, volume depletion, or decreased cardiac output. While it reduces the glomerular filtration rate, it does not involve an obstruction within the urinary collecting system.
Correct Answer is C
Explanation
A. Inspiratory crackles over the lung bases are clinical findings often associated with restrictive lung diseases or heart failure involving pulmonary edema. In chronic bronchitis, the primary issue is airway obstruction rather than alveolar fluid or interstitial fibrosis. While some secretions may cause coarse rales, fine basal crackles are not the defining feature of this condition.
B. Increased resonance, or hyperresonance, upon percussion is a classic finding in emphysema due to alveolar destruction and subsequent air trapping. In chronic bronchitis, the lung parenchyma often remains intact, and percussion notes may be normal. Hyperresonance indicates a loss of lung density that is specifically characteristic of the hyperinflated state of emphysema patients.
C. A prolonged expiratory phase is a hallmark physical finding of obstructive lung diseases, including chronic bronchitis. This occurs because inflammatory narrowing of the bronchioles increases airway resistance, making it more difficult and time-consuming for air to exit the lungs. This physiological delay is a compensatory mechanism to maintain airway pressure and facilitate more complete exhalation.
D. Decreased tactile fremitus occurs when there is an increase in the air-to-tissue ratio, such as in emphysema or a pneumothorax. In chronic bronchitis, the presence of excessive mucus and bronchial wall thickening may actually maintain or slightly increase the transmission of vocal vibrations. Decreased fremitus is not a sensitive or specific diagnostic sign for simple chronic bronchitis.
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