A 54-year-old man comes to the emergency department due to progressive shortness of breath, lower extremity swelling, and decreased urine output for the past week. The patient has a history of nonischemic cardiomyopathy and heart failure with reduced ejection fraction. Medications include metoprolol succinate, lisinopril, spironolactone, and furosemide. He has been on stable doses of medication for the past 6 months but admits that he "misses some doses now and then." Temperature is 98.5 F (36.9 C), blood pressure is 112/64 mm Hg, pulse is 90/min, and respirations are 20/min. Oxygen saturation is 93% on room air. Physical examination shows jugular venous distension. S1 and S2 are normal and there are no murmurs. An S3 is heard. Crackles are heard at the bilateral lung bases. The abdomen is distended and there is 2+ pitting lower extremity edema bilaterally. Laboratory results (current and from 3 weeks ago) are as follows: Urinalysis is unremarkable. Which of the following is the most likely cause of this patient's acute kidney injury?

Question

A 54-year-old man comes to the emergency department due to progressive shortness of breath, lower extremity swelling, and decreased urine output for the past week.  The patient has a history of nonischemic cardiomyopathy and heart failure with reduced ejection fraction.  Medications include metoprolol succinate, lisinopril, spironolactone, and furosemide.  He has been on stable doses of medication for the past 6 months but admits that he "misses some doses now and then."  Temperature is 98.5 F (36.9 C), blood pressure is 112/64 mm Hg, pulse is 90/min, and respirations are 20/min.  Oxygen saturation is 93% on room air.  Physical examination shows jugular venous distension.  S1 and S2 are normal and there are no murmurs.  An S3 is heard.  Crackles are heard at the bilateral lung bases.  The abdomen is distended and there is 2+ pitting lower extremity edema bilaterally.  Laboratory results (current and from 3 weeks ago) are as follows:  Urinalysis is unremarkable.  Which of the following is the most likely cause of this patient's acute kidney injury?

Quizplus · Accepted Answer

11ec25c8_d4d3_5845_bc81_f58e075e4d90_MD0003_00 This patient has acute kidney injury (AKI) with elevated blood urea nitrogen/creatinine ratio (>20:1) and unremarkable urinalysis suggesting a prerenal etiology. Although prerenal AKI usually results from total body volume depletion, it can also occur in volume overloaded states that involve reduced effective arterial blood volume (EABV). This patient has volume overload due to an acute heart failure exacerbation, and his AKI is most likely due to cardiorenal syndrome. Cardiorenal syndrome involves mutually detrimental interactions between the heart and the kidneys. Left ventricular failure with reduced cardiac output leads to decreased renal perfusion followed by activation of the renin-angiotensin-aldosterone system (RAAS). The increase in RAAS activity causes vasoconstriction and volume retention, which increase the load on the left ventricle and further reduce renal perfusion. Cardiorenal syndrome Elevated central venous pressure is likely the major driver of AKI in cardiorenal syndrome. The elevated CVP leads to elevated renal venous pressure and congestion. This reduces the glomerular capillary filtration gradient, possibly due to interstitial edema (from venous congestion) increasing Bowman space hydrostatic pressure; the result is a reduction in glomerular filtration rate (GFR). Decreased renal perfusion due to reduced cardiac output also plays a role in the reduced GFR. It follows that diuretics are usually the most effective therapy for AKI due to cardiorenal syndrome; the resulting reduction in renal venous pressure restores the glomerular capillary filtration gradient and improves GFR. filtration gradient (Choice B) Glomerular hyperfiltration occurs in the early stages of diabetic nephropathy and is recognized by a temporary increase in GFR (leading to a decrease in serum creatinine). (Choice C) Low blood oncotic pressure occurs in nephrotic syndrome, but it is not typical of heart failure. Nephrotic syndrome involves total body volume overload with intravascular volume depletion, and prerenal AKI can occur due to reduced EABV. (Choice D) Left ventricular preload, or end-diastolic volume, is increased in heart failure. Patients with prerenal AKI due to volume depletion (eg, dehydration) have reduced left ventricular preload. (Choice E) Renal artery stenosis is a potential cause of prerenal AKI, but cardiorenal syndrome is more likely in this patient with an acute heart failure exacerbation. Educational objective: Prerenal acute kidney injury (AKI) can occur in volume overloaded states. Prerenal AKI in an acute heart failure exacerbation is most likely due to cardiorenal syndrome, which involves elevated central venous and renal venous pressure leading to a reduction in glomerular filtration. References: Cardiorenal syndrome in acute decompensated heart failure. (http://www.ncbi.nlm.nih.gov/pubmed/19965544)

A 54-Year-Old Man Comes to the Emergency Department Due to Progressive