What can result when the GFR drops below 5%?

When the glomerular filtration rate (GFR) drops below 5%, it indicates significant kidney impairment and a near-total loss of kidney function. In this state, the kidneys are no longer able to effectively excrete potassium, leading to its accumulation in the bloodstream. This condition, known as hyperkalemia, can result in serious complications, including cardiac dysrhythmias.

As potassium levels rise, dietary and pharmacologic management involving potassium restriction becomes crucial to prevent further increases in serum potassium, which can be life-threatening. The severity of hyperkalemia depends on the degree of kidney dysfunction, and when GFR is critically low, the ability of the body to regulate potassium through renal excretion is severely compromised.

In the context of kidney failure, the other conditions listed do not accurately reflect the typical metabolic derangements associated with such a low GFR. For instance, hypernatremia usually arises from excess sodium retention, while hypokalemia is associated with inadequate potassium, not its excess. Hypophosphatemia is relatively less common in severe renal failure; rather, hyperphosphatemia frequently occurs due to impaired excretion. Thus, the major concern with a GFR under 5% is the management of elevated potassium levels, necess