Internal Medicine Exam Acute Kidney Injury 5 — Questions and Answers
Question 1: A 55-year-old man with multiple myeloma presents with AKI, hypercalcemia, and Bence Jones proteinuria. Which mechanism directly causes AKI in this condition?
- Light chain cast nephropathy obstructing tubular lumens (Correct answer)
- Immune complex deposition in glomeruli
- NSAIDs used for bone pain
- Amyloid deposition causing nephrotic syndrome exclusively
Correct answer: Light chain cast nephropathy obstructing tubular lumens
Myeloma cast nephropathy occurs when light chains (Bence Jones proteins) precipitate with Tamm-Horsfall protein in distal tubules, forming obstructing casts that cause AKI.
Question 2: Which approach to fluid resuscitation in AKI has been shown to be superior to normal saline in reducing the risk of hyperchloremic metabolic acidosis and worsening renal function?
- Dextrose 5% in water (D5W)
- Albumin 5% infusion
- Balanced crystalloids (Lactated Ringer's or PlasmaLyte) (Correct answer)
- Hypertonic saline 3%
Correct answer: Balanced crystalloids (Lactated Ringer's or PlasmaLyte)
Balanced crystalloids have lower chloride content than normal saline and have been shown in trials (SMART, SALT-ED) to reduce rates of major adverse kidney events.
Question 3: A 35-year-old pregnant woman at 36 weeks gestation develops AKI with thrombocytopenia, microangiopathic hemolytic anemia, and elevated liver enzymes. What is the most likely diagnosis?
- Acute fatty liver of pregnancy
- HELLP syndrome (Correct answer)
- Thrombotic thrombocytopenic purpura
- Pre-eclampsia without HELLP
Correct answer: HELLP syndrome
HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) can cause AKI through TMA and is a severe complication of pre-eclampsia requiring urgent delivery.
Question 4: A 70-year-old man with AKI, low complement (C3, C4), RBC casts, and a history of recent streptococcal skin infection is most likely experiencing:
- IgA nephropathy (Berger's disease)
- Post-infectious (post-streptococcal) glomerulonephritis (Correct answer)
- Membranous nephropathy
- Rapidly progressive glomerulonephritis from ANCA vasculitis
Correct answer: Post-infectious (post-streptococcal) glomerulonephritis
Post-streptococcal glomerulonephritis presents 1–4 weeks after skin or throat infection with RBC casts, complement consumption (low C3), and nephritic syndrome.
Question 5: During evaluation of AKI, a renal ultrasound shows bilateral small echogenic kidneys. What does this finding most likely indicate?
- Acute tubular necrosis (reversible)
- Chronic kidney disease as the underlying condition, not true AKI (Correct answer)
- Polycystic kidney disease
- Bilateral renal artery stenosis
Correct answer: Chronic kidney disease as the underlying condition, not true AKI
Small echogenic kidneys on ultrasound indicate chronic scarring and fibrosis, suggesting the elevated creatinine reflects CKD rather than a true acute process.
Question 6: Which renal replacement therapy modality is preferred in hemodynamically unstable ICU patients with AKI?
- Intermittent hemodialysis (IHD)
- Continuous renal replacement therapy (CRRT) (Correct answer)
- Peritoneal dialysis
- Sustained low-efficiency dialysis (SLED) only
Correct answer: Continuous renal replacement therapy (CRRT)
CRRT is preferred in hemodynamically unstable patients because it removes solutes and fluid slowly and continuously, minimizing hypotension compared to intermittent hemodialysis.
Question 7: A patient recovering from AKI due to sepsis now has a urine output of 4 L/day with a fixed urine osmolality of 310 mOsm/kg. This pattern is most consistent with which phase of AKI recovery?
- Oliguric phase
- Anuric phase
- Polyuric recovery phase with impaired tubular concentrating ability (Correct answer)
- Complete recovery with normal tubular function
Correct answer: Polyuric recovery phase with impaired tubular concentrating ability
The polyuric phase of ATN recovery shows high urine volume but isosthenuria (fixed osmolality ~300 mOsm/kg) due to persistent tubular dysfunction before full recovery.
Internal Medicine Exam Acute Kidney Injury 5
A 55-year-old man with multiple myeloma presents with AKI, hypercalcemia, and Bence Jones proteinuria.
Which mechanism directly causes AKI in this condition?