NCLEX Memory Hint: Renal Dysfunction

Lab Values: Renal Dysfunction 

There is a broad range of dysfunction which can occur with the kidneys. Renal insufficiency is frequently seen in the elderly and in those with hypertension and is evidenced by a glomerular filtration rate (GFR) of < 30%. Renal failure can be acute, chronic, or end stage. End-stage is a GFR of < 15% and dialysis is required to live. There are numerous causes of chronic renal failure including diabetes and hypertension. While these conditions cause renal failure, renal failure also leads to diabetes because of the insulin resistance that develops, and it also leads to hypertension. 

Renal insufficiency

In renal insufficiency, the kidneys lose the ability to hold onto sodium and water. Thus, urine output is increased. ACE inhibitors or angiotensin receptor blockers will be started to preserve renal function. If the GFR falls, these drugs will be stopped due to associated hyperkalemia in the presence of renal dysfunction. The urine will also be monitor for protein because nephrotic syndrome is an adverse effect of the drugs. 

Acute renal failure

Acute renal failure is also known as acute kidney injury (AKI). It is a sudden and almost complete loss of the function of the kidneys over a short period of time. Types include pre-renal due to decreased perfusion to the kidneys, intra-renal due to damage to thekidneys, and post-renal due to obstruction of urine from the kidneys. 

The phases of acute renal failure include initiation, maintenance (diuretic), and recovery which could take up to one year. In the diuretic phase, urinary output may be up to 10 liters a day. The initiation phase will be oliguric or non-oliguric depending on the cause. Oliguric occurs with decreased perfusion and is the most common. Non-oliguric is caused by nephrotoxic drug therapy. 

Chronic renal failure

Progressive failure of the kidneys is seen in chronic renal failure. BUN and creatinine will be increased, and potassium may be controlled with diet and avoidance of medications with potassium. In end-stage renal failure, the potassium level may increase to a dangerous level. ECG changes may be seen starting at a level of 5.5 mEq/L. Cardiac arrest can occur with high levels.  

Other significant lab abnormalities with chronic renal failure: 

• Phosphorus and magnesium will increase due to the reduced renal excretion. 

• Calcium will decrease due to inadequate conversion of vitamin D leading to decreased absorption of calcium from the intestines. 

• PT and PTT increase due to platelet dysfunction leading to an increased risk of bleeding. 

• As protein is lost in the urine, serum albumin levels decrease. 

• RBC decrease due to the inability of the kidneys to produce erythropoietin. 

• Uric acid will increase leading to gout and other complications. 

• Metabolic acidosis will develop and pH, HCO₃, and venous CO₂ will be low. 

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