A nurse is reviewing the BUN and creatinine levels of an older adult client who has chronic kidney disease. The nurse should expect which of the following findings?

Choice A rationale These values fall within the standard physiological reference ranges for a healthy adult. A blood urea nitrogen level of 8 mg/dL is within the normal 7 to 20 mg/dL range, while a creatinine of 0.7 mg/dL is normal for females (0.6 to 1.1 mg/dL). In chronic kidney disease, the glomerular filtration rate significantly decreases, leading to the systemic accumulation of these nitrogenous wastes rather than maintaining these low, healthy baseline concentrations. Choice B rationale A blood urea nitrogen of 10 mg/dL is normal, but a creatinine level of 0.3 mg/dL is considered low, often seen in cases of severe muscle wasting or advanced malnutrition rather than renal failure. In chronic kidney disease, the pathology involves a progressive loss of functional nephrons. This structural damage prevents the effective clearance of creatinine from the blood, causing serum levels to rise significantly above the normal 0.6 to 1.3 mg/dL range instead of decreasing. Choice C rationale While a blood urea nitrogen of 23 mg/dL is slightly elevated above the normal limit of 20 mg/dL, the creatinine level of 1.0 mg/dL remains perfectly within the normal reference range of 0.6 to 1.2 mg/dL for adults. This specific combination does not reflect the significant biochemical markers of chronic kidney disease. In true renal failure, both values typically rise in tandem as the kidneys lose their ability to filter and excrete metabolic byproduct effectively. Choice D rationale These elevated values are characteristic of stage 4 or 5 chronic kidney disease where azotemia is prominent. A blood urea nitrogen of 45 mg/dL is more than double the normal maximum of 20 mg/dL, and a creatinine of 8 mg/dL is severely elevated above the normal 1.3 mg/dL limit. This indicates a profound reduction in the glomerular filtration rate, as the kidneys can no longer excrete these waste products, leading to their dangerous accumulation in the blood.