How would you answer this question?
Mrs. Mersa is admitted with sepsis and hypotension. Her labs indicate:
BUN 58 mg/dl
Serum creatinine 2.1 mg/dl
Urine sodium 70 mEq/L
Urine specific gravity 1.010, with cellular casts and RBCs in the urine.
Based on these findings you would consider:
a. Chronic renal insufficiency.
b. Prerenal failure.
c. Postrenal failure.
d. Acute tubular necrosis.
The correct answer is "d" acute tubular necrosis.
The key to finding the correct answer in this situation is the history of sepsis. Sepsis causes damage directly to the nephron by "burning holes" in the filter of the kidney, the glomerulus. Damaging effects of systemic inflammation cause the glomerulus to become porous, and it is this destruction of the internal workings of the kidney that is called acute tubular necrosis. The damage caused by sepsis inflammation causes the glomerulus to become more porous than usual and that is why Mrs. Mersa has a low specific gravity, casts and RBCs in her urine.
Hypotension can cause prerenal failure, but would be associated with "hanging on" to fluid as evidenced by a high urine specific gravity (concentrated urine). Postrenal failure is caused by blockage of the urinary tract such as what happens with bladder tumors or an obstructed urinary catheter.
Chronic renal insufficiency can cause an elevated BUN and creatinine, but would not be associated with the urinary findings.
Watch for changes in urinary flow and color in your patients with sepsis and hypotension, acute renal failure can be precipitated by these conditions.
Best wishes,
David W. Woodruff, MSN, RN-BC, CNS, CEN
President, Ed4Nurses, Inc.
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