A 19-year-old man presents to the emergency department after a motor vehicle accident. The patient reports left shoulder pain that worsens with deep inspiration. Medical history is significant for a recent diagnosis of infectious mononucleosis. His temperature is 99°F (37.2°C), blood pressure is 80/55 mmHg, pulse is 115/min, and respiratory rate is 22/min. On physical exam, there is abdominal guarding, abdominal tenderness in the left upper quadrant, and rebound tenderness. The patient’s mucous membranes are dry and skin turgor is reduced. Which of the following most likely represents the acute changes in renal plasma flow (RPF) and glomerular filtration rate (GFR) in this patient?

Decreased RPF and decreased GFR

No change in RPF and decreased GFR

No change in RPF and increased GFR

Decreased RPF and no change in GFR

A 33-year-old man presents to the emergency department because of an episode of bloody emesis. He has had increasing dyspnea over the past 2 days. He was diagnosed with peptic ulcer disease last year. He has been on regular hemodialysis for the past 2 years because of end-stage renal disease. He skipped his last dialysis session because of an unexpected business trip. He has no history of liver disease. His supine blood pressure is 110/80 mm Hg and upright is 90/70, pulse is 110/min, respirations are 22/min, and temperature is 36.2°C (97.2°F). The distal extremities are cold to touch, and the outstretched hand shows flapping tremor. A bloody nasogastric lavage is also noted, which eventually clears after saline irrigation. Intravenous isotonic saline and high-dose proton pump inhibitors are initiated, and the patient is admitted into the intensive care unit. Which of the following is the most appropriate next step in the management of this patient?

Observation in the intensive care unit

Transfusion of packed red blood cells

A 50-year-old man with a history of stage 4 kidney disease was admitted to the hospital for an elective hemicolectomy. His past medical history is significant for severe diverticulitis. After the procedure he becomes septic and was placed on broad spectrum antibiotics. On morning rounds, he appear weak and complains of fatigue and nausea. His words are soft and he has difficulty answering questions. His temperature is 38.9°C (102.1°F), heart rate is 110/min, respiratory rate is 15/min, blood pressure 90/65 mm Hg, and saturation is 89% on room air. On physical exam, his mental status appears altered. He has a bruise on his left arm that spontaneously appeared overnight. His cardiac exam is positive for a weak friction rub. Blood specimens are collected and sent for evaluation. An ECG is performed (see image). What therapy will this patient most likely receive next?

Send the patient for hemodialysis

Perform a STAT pericardiocentesis

Prepare the patient for renal transplant

Treat the patient with cyclophosphamide and prednisone

A 56-year-old woman presents to the emergency department with muscle weakness. She reports her symptoms have progressively worsened over the course of 2 weeks and are most significant in her lower extremities. She also notices increased urinary frequency. Approximately 1 month ago she was diagnosed with a calcium phosphate nephrolithiasis. Medical history is significant for rheumatoid arthritis diagnosed approximately 10 years ago treated with methotrexate, and type II diabetes mellitus treated with metformin. Her temperature is 98.6°F (37°C), blood pressure is 138/92 mmHg, pulse is 92/min, and respirations are 17/min. On physical exam, there is mild tenderness to palpation of the metacarpophalangeal and proximal interphalangeal joints. There is 4/5 power throughout the lower extremity. Laboratory testing is shown. Serum: Na+: 137 mEq/L Cl-: 106 mEq/L K+: 2.9 mEq/L HCO3-: 18 mEq/L Glucose: 115 mg/dL Creatinine: 1.0 mg/dL Urine pH: 5.6 Which of the following is the best next step in management?

Begin potassium replacement therapy with dextrose

Administer intravenous sodium bicarbonate

A 58-year-old man is brought to the Emergency Department after 2 days of shortness of breath, orthopnea, and lower limb edema. His past medical history is significant for hypertension and a myocardial infarction 3 years ago that required a coronary arterial bypass graft. He has not been able to take prescribed medicine in several months due to recent unemployment and issues with insurance. On admission, his blood pressure is 155/92 mmHg, heart rate is 102/min, respiratory rate is 24/min, and temperature is 36.4°C (97.5°F). On physical examination there are fine rales in both lungs, regular and rhythmic cardiac sounds with an S3 gallop and a grade II/VI holosystolic murmur. Initial laboratory tests are shown below: Na+ 140 mEq/L K+ 4.2 mEq/L Cl- 105 mEq/L BUN 20 mg/dL Creatinine 0.8 mg/dL The patient is stabilized and admitted to the hospital. The next day his blood pressure is 110/60 mmHg, heart rate is 110/min, respiratory rate is 18/min, and temperature is 36.4°C (97.5°F). This morning's laboratory tests are shown below: Na+ 135 mEq/L K+ 3.2 mEq/L Cl- 102 mEq/L BUN 45 mg/dL Creatinine 1.7 mg/dL Which of the following best explains the changes seen in this patient?

Glomerular basement membrane damage

You are called to a hemodialysis suite. The patient is a 61-year-old man with a history of hypertension, hypercholesterolemia, and type-2 diabetes mellitus-induced end-stage renal disease who has required hemodialysis for the past year. His current hemodialysis session is nearing the end when the nurse notices that his blood pressure has dropped to 88/60 mm Hg from his normal of 142/90 mm Hg. The patient denies any shortness of breath or chest pain. He took his daily bisoprolol, metformin, and insulin this morning before coming to the hospital. On examination, the patient’s blood pressure is 92/60 mm Hg, and his heart rate is 119/min. Chest auscultation is unremarkable. What is the most appropriate next management step?

Stop ultrafiltration and decrease blood flow into the machine

Administer intravenous calcium gluconate

Transfuse the patient with 1 unit of packed red blood cells

Start the patient on an epinephrine drip

Renal replacement therapy for USMLE Step 3: High-Yield Internal Medicine Lessons

Indications for RRT - The 'AEIOU' Vowels

📌 AEIOU

Acidosis: Severe, refractory metabolic acidosis (e.g., pH < 7.1).
Electrolytes: Symptomatic or severe, refractory hyperkalemia (e.g., K⁺ > 6.5 mEq/L with EKG changes).
Intoxications: Acute poisoning with a dialyzable substance.
- 📌 SLIME: Salicylates, Lithium, Isopropanol, Methanol, Ethylene glycol.
Overload: Refractory fluid overload (e.g., pulmonary edema unresponsive to diuretics).
Uremia: Symptomatic manifestations.
- Uremic pericarditis.
- Uremic encephalopathy (asterixis, confusion, seizure).

⭐ Uremic pericarditis is an absolute indication for immediate dialysis, regardless of the BUN and creatinine values.

AEIOU Mnemonic for Acute Dialysis Indications

RRT Modalities - The Kidney's Helpers

Hemodialysis (HD): Blood filtered externally via an artificial membrane (dialyzer). Requires vascular access.
- Access: AV Fistula (best), AV Graft, or Central Venous Catheter (highest infection risk).
- Schedule: Typically 3-4 hours, 3x/week in-center.
Peritoneal Dialysis (PD): Uses the peritoneal membrane as the endogenous filter. Dialysate is instilled into the peritoneal cavity.
- Types: Continuous Ambulatory (CAPD) or Automated (APD).
- Major Risk: Peritonitis (cloudy effluent, abdominal pain).
Continuous RRT (CRRT): Slow, continuous filtration for hemodynamically unstable ICU patients.

Feature	Hemodialysis (HD)	Peritoneal Dialysis (PD)
Location	Center/Hospital	Home
Principle	Diffusion/Convection	Osmosis/Diffusion
Pros	High efficiency	Lifestyle flexibility
Cons	↓ BP, access issues	Peritonitis, hyperglycemia

Hemodialysis vs. Peritoneal - The Great Debate

Peritoneal Dialysis Setup

Feature	Hemodialysis (HD)	Peritoneal Dialysis (PD)
Location	Hospital or dialysis center	Home-based, daily
Access	AV fistula/graft or central venous catheter	Tenckhoff catheter (peritoneal)
Schedule	3-4 hours, 3 times/week	Continuous (CAPD) or nightly (APD)
Mechanism	Solute diffusion across a semipermeable membrane in an external dialyzer. Rapid fluid/solute removal.	Peritoneal membrane is the endogenous dialyzer. Slower, more physiologic process.
Complications	Hypotension, muscle cramps, disequilibrium syndrome, access-related infection/thrombosis.	Peritonitis (cloudy fluid, abdominal pain), hyperglycemia, catheter site infection.

Complications - When Good Filters Go Bad

Hemodialysis (HD)
- Hypotension: Most common acute complication from rapid ultrafiltration.
- Dialysis Disequilibrium Syndrome: Cerebral edema from rapid solute removal. Presents with headache, nausea, confusion, seizures.
- Access Issues: Infection (S. aureus), thrombosis, stenosis, aneurysm.
- Chronic: Dialysis-related amyloidosis (DRA) from ↑ β2-microglobulin deposition.
Peritoneal Dialysis (PD)
- Infection: Peritonitis (cloudy effluent, abdominal pain), exit-site/tunnel infections.
- Metabolic: Hyperglycemia (dextrose in dialysate), dyslipidemia.
- Mechanical: Hernias, dialysate leaks, catheter obstruction.

Anatomy of the wrist and carpal tunnel

⭐ High-Yield: Dialysis-related amyloidosis (DRA) classically presents with carpal tunnel syndrome, scapulohumeral periarthritis, and bone cysts. It is a result of β2-microglobulin accumulation over years of dialysis.

High‑Yield Points - ⚡ Biggest Takeaways

Urgent dialysis indications follow the AEIOU mnemonic: severe Acidosis, Electrolyte imbalance (K⁺ >6.5), Intoxication, fluid Overload, and Uremic symptoms (pericarditis, encephalopathy).

AV fistula is the preferred hemodialysis access due to the lowest infection and thrombosis risk.

Hypotension is the most common hemodialysis complication; peritonitis is the major risk with peritoneal dialysis.

Dialysis disequilibrium syndrome results from rapid urea removal causing cerebral edema.

CRRT is reserved for hemodynamically unstable patients.

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