Acute renal failure can lead to which of the following?

Acute renal failure often results in the kidneys being unable to filter waste products effectively. One of the significant consequences of this impaired function is fluid retention, as the kidneys cannot excrete enough water and solutes. This retention can lead to symptoms such as swelling in the extremities and changes in blood pressure, which is critical to monitor in patients with acute renal failure.

Other options may be associated with renal conditions, but they do not represent the primary and direct consequence of acute renal failure as clearly as fluid retention does. Loss of appetite can occur but is often a secondary effect rather than a primary symptom. Increased urine output is typically not seen in acute renal failure; rather, urine output is usually decreased. Muscle cramps can occur due to electrolyte imbalances but aren't a defining characteristic of acute kidney failure itself. Fluid retention stands out as a direct and significant complication of acute renal failure, highlighting its impact on the body’s fluid balance.