A 74-year-old woman is brought to the emergency department with fever, chills, and shortness of breath. Two days ago, she choked while having tea and doughnuts and almost lost consciousness. Her son performed the Heimlich maneuver. The patient has advanced Alzheimer dementia, and her son is her health care proxy and primary caregiver; her 73-year-old husband also participates in her care. Her other medical problems include hypertension, hyperlipidemia, coronary heart disease, ischemic stroke with mild residual right hemiparesis, history of heme-positive stools, and urine incontinence. She is allergic to penicillin (anaphylaxis). Her temperature is 38.9 C (102 F), blood pressure is 120/80 mm Hg, pulse is 92/min, and respirations are 24/min. Pulse oxymetry shows 89% on room air and 94% on 40% facemask oxygen. Auscultation of the chest shows crackles at the right lung base. The heart sounds are regular. There is no jugular venous distension. The abdomen is soft, nontender, and nondistended. There is no peripheral edema. Laboratory results are as follows: A portable chest x-ray shows a right lower-lobe infiltrate.
During the night, the patient deteriorates and becomes more hypoxic, requiring 100% oxygen by facemask. Her son refuses to have her intubated. She has several episodes of hypotension. Aggressive intravenous fluid therapy is given, and a Foley catheter is placed. Her blood pressure normalizes. Over the course of the next 12 hours, her urine output drops to 5 mL/hr. On the 4th day of hospitalization, her temperature is 37.3 C (99.1 F), blood pressure is 122/70 mm Hg, and pulse is 78/min. Despite receiving intravenous fluids, her urine output remains low. Laboratory results are as follows:
Further evaluation of this patient would most likely show which of the following?

Question

A 74-year-old woman is brought to the emergency department with fever, chills, and shortness of breath.  Two days ago, she choked while having tea and doughnuts and almost lost consciousness.  Her son performed the Heimlich maneuver.  The patient has advanced Alzheimer dementia, and her son is her health care proxy and primary caregiver; her 73-year-old husband also participates in her care.  Her other medical problems include hypertension, hyperlipidemia, coronary heart disease, ischemic stroke with mild residual right hemiparesis, history of heme-positive stools, and urine incontinence.  She is allergic to penicillin (anaphylaxis).  Her temperature is 38.9 C (102 F), blood pressure is 120/80 mm Hg, pulse is 92/min, and respirations are 24/min.  Pulse oxymetry shows 89% on room air and 94% on 40% facemask oxygen.  Auscultation of the chest shows crackles at the right lung base.  The heart sounds are regular.  There is no jugular venous distension.  The abdomen is soft, nontender, and nondistended.  There is no peripheral edema.  Laboratory results are as follows:  A portable chest x-ray shows a right lower-lobe infiltrate.
During the night, the patient deteriorates and becomes more hypoxic, requiring 100% oxygen by facemask.  Her son refuses to have her intubated.  She has several episodes of hypotension.  Aggressive intravenous fluid therapy is given, and a Foley catheter is placed.  Her blood pressure normalizes.  Over the course of the next 12 hours, her urine output drops to 5 mL/hr.  On the 4th day of hospitalization, her temperature is 37.3 C (99.1 F), blood pressure is 122/70 mm Hg, and pulse is 78/min.  Despite receiving intravenous fluids, her urine output remains low.  Laboratory results are as follows:
 Further evaluation of this patient would most likely show which of the following?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfd8_0b30_8f63_e9e6806d1a8b_MD0005_00 This patient has most likely developed acute tubular necrosis (ATN), which is responsible for most cases of acute renal failure in hospitalized patients. The etiopathology generally involves a perfusion deficit due to hypovolemia, hypotension, shock, sepsis, or low cardiac output states. The typical presentation is oliguria following a hypotensive episode, with elevated blood urea nitrogen and creatinine levels (though the ratio is typically normal) and anion gap acidosis. Examination of the urinary sediment usually shows characteristic "muddy brown" casts. "muddy brown" casts (Choice A) Prerenal azotemia is associated with decreased fractional excretion of sodium; however, once ATN sets in, the fractional excretion of sodium increases (usually >2). Response to a fluid challenge is the gold standard in distinguishing prerenal azotemia (which responds to a fluid challenge with improved urine output) from ATN. This patient's low urine output and elevated creatinine despite receiving continuous intravenous hydration and showing no signs of hypovolemia (normotension, no tachycardia) suggest ATN. (Choice B) In patients with oliguria, it is always important to consider obstructive uropathy. This diagnosis is more likely if there is a history of such conditions as renal colic, pelvic or retroperitoneal malignancy, or history of radiation. Benign prostatic hyperplasia is the most common cause of obstructive uropathy. This diagnosis is less likely in women, particularly those with a Foley catheter in place. (Choice C) Eosinophils are seen in the urine of patients with drug-induced allergic interstitial nephritis (AIN). This patient's clinical picture is not consistent with AIN, which is usually seen 3-5 days (and rarely in the first 2 days) after the administration of antibiotics. (Choice E) Red cell casts in the urine are indicative of glomerulonephritis. Educational objective: Acute tubular necrosis should be suspected in patients with oliguria following a hypotensive episode. Muddy brown casts and high fractional excretion of sodium differentiate acute tubular necrosis from prerenal azotemia. References: Diagnostic value of urine microscopy for differential diagnosis of acute kidney injury in hospitalized patients. (http://www.ncbi.nlm.nih.gov/pubmed/18784207)

A 74-Year-Old Woman Is Brought to the Emergency Department with Fever