What laboratory value change should indicate to a nurse that a patient with renal failure has entered the oliguric stage?

A. Hypertension as a result of the increased, concentrated blood volume: Hypertension in chronic kidney disease is due to fluid overload and renin-angiotensin-aldosterone system activation, not erythropoietin deficiency.

B. Elevated lipid levels in the bloodstream, contributing to accelerated atherosclerosis: Dyslipidemia in chronic kidney disease is unrelated to erythropoietin deficiency.

C. Anemia as a result of the diminished number of red blood cells being produced: Erythropoietin stimulates red blood cell production; its deficiency in chronic renal failure leads to anemia.

D. Diminished immunologic function with fewer white blood cells: White blood cell production is not directly affected by erythropoietin deficiency.

A. Blood volume decreases: While fluid imbalances are common in renal failure, the oliguric stage is marked by fluid retention, not decreased blood volume.

B. Blood urea nitrogen (BUN) level rises: The oliguric stage is characterized by reduced urine output, leading to waste product accumulation, including elevated BUN levels.

C. Urine osmolality increases: In renal failure, urine osmolality may remain low or not reflect changes due to impaired kidney function.

D. Serum calcium increases: Serum calcium often decreases in renal failure due to disturbances in vitamin D metabolism and phosphate retention.