Urinary Disorders Q 108

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Which cause of hypertension is the most common in acute renal failure?

  

    A. Pulmonary edema

    B. Hypervolemia

    C. Hypovolemia

    D. Anemia

    

    

Correct Answer: B. Hypervolemia

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Acute renal failure causes hypervolemia as a result of overexpansion of extracellular fluid and plasma volume with the hypersecretion of renin. Therefore, hypervolemia causes hypertension. Fluid overload leads to endothelial dysfunction due to inflammation and ischemia-reperfusion injury, causing damage to glycocalyx and capillary leakage. Capillary leakage leads to interstitial edema and at the same time, due to significant loss of volume to the interstitial compartment, there is reduction in circulating intravascular volume. This may then lead to reduction in renal perfusion pressure and subsequently to AKI.

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Option A: Interstitial edema leads to impairment in the diffusion of oxygen and metabolites from capillaries to tissues. Interstitial edema increases tissue pressure and leads to obstruction of lymphatic drainage and disturbance in cell-to-cell interaction, which will lead to progressive organ failure. The kidney’s ability to accommodate increasing hydrostatic interstitial pressures is limited due to renal capsule, and thus all these effects are more prominently seen in the kidney.

Option C: Fluid overload is also known to cause distension of atria and stretching of vessel walls, causing a release of ANP, which further leads to EGL damage, and cascade leads to AKI. Massive fluid resuscitation and positive fluid balance are known risk factors for intra-abdominal hypertension (IAH) development. Elevated IAP leads to compression of intra-abdominal vessels causing compromised microvascular blood flow and increased renal venous congestion. This results in impaired renal plasma flow and decreased glomerular filtration rate, causing AKI.

Option D: Acute kidney injury can be classified based on the causative factor into intrinsic renal, prerenal, and postrenal AKI. Prerenal causes contribute to the majority of community-acquired cases of AKI. In the case of prerenal AKI, fluid resuscitation is the gold standard, but if this resuscitation continues beyond the correction of hypovolemia, then it is associated with increased morbidity, mortality, and length of hospital stay as well as increased risk of AKI.

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