Acute Kidney Injury
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USMLE Step 2 CK › Acute Kidney Injury
A 58-year-old patient undergoes abdominal aortic aneurysm repair. Estimated blood loss is 2.2 L; they receive 3 units packed RBCs and 3 L crystalloid. Post-op, they are oliguric and hypotensive. Vitals: BP 86/52 mm Hg, HR 122/min. Exam shows cool extremities and dry mucous membranes; lungs clear. Labs: creatinine rises from 1.1 to 2.5 mg/dL, BUN 62 mg/dL. Urinalysis is bland. The most likely cause of this acute kidney injury is reduced kidney perfusion due to perioperative volume loss and hypotension.
Medication-related kidney injury from new antibiotic
Kidney injury from urinary obstruction at the bladder
Prerenal acute kidney injury from hypovolemia
Kidney filter inflammation after recent infection
Chronic kidney disease from long-standing hypertension
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards pre-renal AKI, such as reduced kidney perfusion due to perioperative volume loss and hypotension. The correct choice, B, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, A, fails because it suggests obstruction without supporting findings, often due to misunderstanding of pre-renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.
A 61-year-old patient undergoes bowel resection with 1.6 L blood loss and receives 2 units packed RBCs and 2 L crystalloid. Post-op, urine output falls and BP remains low. Vitals: BP 90/58 mm Hg, HR 112/min. Exam shows dry mucous membranes and cool extremities. Labs: creatinine rises from 0.9 to 2.0 mg/dL, BUN 50 mg/dL. Urinalysis is bland. Which of the following is the most appropriate next step in management?
Order contrast CT to evaluate renal perfusion
Order urgent dialysis for creatinine rise
Restrict fluids due to oliguria
Start IV loop diuretic to increase urine output
Give isotonic fluids and optimize hemodynamics
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards pre-renal AKI, such as reduced perfusion from perioperative blood loss and hypotension. The correct choice, A, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, C, fails because it restricts fluids in hypovolemia, often due to misunderstanding of pre-renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.
A 60-year-old patient undergoes hip replacement. During surgery, they have transient hypotension to 78/40 mm Hg for 20 minutes after blood loss of 1.2 L; they receive 1 unit packed RBCs and 1 L crystalloid. On post-op day 1, urine output is low despite additional fluids. Vitals: BP 104/66 mm Hg, HR 102/min. Exam shows dry mucous membranes; no edema; lungs clear. Labs: creatinine increases from 1.0 to 1.9 mg/dL, BUN 44 mg/dL. Urinalysis is bland. The team suspects reduced kidney perfusion from perioperative volume loss and low blood pressure.
Increase isotonic fluids and optimize blood pressure
Order renal biopsy to guide therapy urgently
Restrict fluids due to low urine output
Start diuretics to force urine production
Administer NSAIDs for post-operative pain control
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards pre-renal AKI, such as reduced kidney perfusion from perioperative volume loss and low blood pressure. The correct choice, A, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, C, fails because it restricts fluids in hypovolemia, often due to misunderstanding of pre-renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.
A 70-year-old patient with benign prostatic hyperplasia presents with progressive weak stream and new-onset inability to void. They feel suprapubic fullness. Vitals: BP 160/90 mm Hg. Exam shows a distended bladder. Labs: creatinine 3.0 mg/dL (baseline 1.0), BUN 50 mg/dL. Urinalysis shows trace blood. Bedside bladder scan shows large retained volume; ultrasound shows bilateral hydronephrosis. Which of the following is the most appropriate next step in management?
Begin urgent dialysis for creatinine elevation
Place a urinary catheter to relieve obstruction
Start fluid restriction and observe for diuresis
Order MRI pelvis before any intervention
Administer IV loop diuretic to increase output
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards post-renal AKI, such as urinary obstruction from enlarged prostate. The correct choice, A, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, B, fails because it restricts fluids without relieving obstruction, often due to misunderstanding of post-renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.
A 46-year-old patient with no prior renal history starts trimethoprim-sulfamethoxazole for a skin infection 10 days ago. They now present with fatigue, decreased appetite, and reduced urine output. They also note a low-grade fever and diffuse itchy rash. Vitals: T 37.9°C, BP 132/78 mm Hg, HR 92/min. Exam shows a faint maculopapular rash on the trunk; mild flank discomfort to palpation. Labs: serum creatinine 2.6 mg/dL (baseline 0.9), BUN 34 mg/dL. Urinalysis shows mild protein and white cells. The timing after a new medication raises concern for kidney injury related to a drug reaction.
Start ibuprofen for fever and flank discomfort
Discontinue trimethoprim-sulfamethoxazole immediately
Begin urgent dialysis for creatinine elevation alone
Order contrast CT abdomen as first test
Continue antibiotic and add IV fluids only
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards intrinsic AKI, such as kidney injury related to a drug reaction from trimethoprim-sulfamethoxazole. The correct choice, B, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, A, fails because it continues the offending agent without discontinuation, often due to misunderstanding of drug-induced renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.
A 56-year-old patient undergoes elective colectomy. Intraoperatively, estimated blood loss is 1.8 L; they receive 2 units packed RBCs and 2.5 L crystalloid. Post-op, urine output declines to 15 mL/hr for 6 hours despite maintenance fluids. They feel lightheaded when sitting up. Vitals: BP 92/58 mm Hg, HR 118/min. Exam shows cool extremities and dry mucous membranes; lungs are clear; no peripheral edema. Labs: serum creatinine rises from 0.9 mg/dL pre-op to 2.1 mg/dL, BUN 48 mg/dL. Urinalysis is bland without protein or blood. The team suspects decreased kidney perfusion from hypovolemia related to perioperative blood loss and inadequate effective circulating volume.
Order emergent hemodialysis for rising creatinine
Begin fluid restriction to prevent overload
Give isotonic IV fluids and reassess urine output
Start IV vancomycin for presumed infection
Administer IV contrast CT to evaluate kidneys
Explanation
This question tests the ability to recognize and manage Acute Kidney Injury (AKI) in a clinical context. AKI is characterized by a sudden decrease in renal function, often identified by increased serum creatinine and decreased urine output. In this vignette, the patient's history, laboratory findings, and symptoms point towards pre-renal AKI, such as decreased kidney perfusion from hypovolemia related to perioperative blood loss and inadequate effective circulating volume. The correct choice, A, accurately addresses the immediate management or diagnostic need, ensuring patient safety and adherence to medical guidelines. A common distractor, C, fails because it restricts fluids in a hypovolemic state, often due to misunderstanding of pre-renal pathophysiology. Teaching strategies: Encourage students to focus on understanding the pathophysiology of renal conditions and to apply clinical guidelines accurately. Practice scenarios should highlight the differentiation between pre-renal, intrinsic, and post-renal causes to build diagnostic accuracy.