A 38-year-old man comes to the emergency department because he has been vomiting blood. After appropriate resuscitation measures, he undergoes upper gastrointestinal endoscopy, which reveals a bleeding duodenal ulcer. During hospital day 2, the patient develops decreased urine output. Serum creatinine rises to 3.0 mg/dL from a baseline of 1.2 mg/dL. Renal biopsy shows patchy epithelial necrosis of the tubules, tubulorrhexis, and intratubular casts. On hospital day 8, urine output significantly increases and serum creatinine levels decline. Over the next few days, this patient is at highest risk for which of the following complications?

Question

A 38-year-old man comes to the emergency department because he has been vomiting blood.  After appropriate resuscitation measures, he undergoes upper gastrointestinal endoscopy, which reveals a bleeding duodenal ulcer.  During hospital day 2, the patient develops decreased urine output.  Serum creatinine rises to 3.0 mg/dL from a baseline of 1.2 mg/dL.  Renal biopsy shows patchy epithelial necrosis of the tubules, tubulorrhexis, and intratubular casts.  On hospital day 8, urine output significantly increases and serum creatinine levels decline.  Over the next few days, this patient is at highest risk for which of the following complications?

Quizplus · Accepted Answer

11ec160b_3a25_0aa3_9249_3de30d2d3578_MD0001_00 This patient developed acute renal failure after gastrointestinal hemorrhage; renal biopsy showing epithelial necrosis of the tubules, tubulorrhexis, and intratubular casts is consistent with acute tubular necrosis (ATN). ATN is characterized by tubular injury due to renal ischemia (eg, shock, hemorrhage) or direct cytotoxicity (eg, radiologic contrast agents, aminoglycosides). The clinical course of ATN can be broken into 3 stages. The initiation stage is marked by the inciting event (eg, hemorrhage, as in this patient) and the onset of tubular injury. If significant tubular damage occurs, the maintenance stage (oliguric stage) follows in 24-36 hours. During this stage, urine output decreases and patients may develop volume overload. Renal tubular dysfunction results in the characteristic low urinary osmolality (<350 mOsm/kg), high urinary sodium (>30 mEq/L), and high urinary fractional sodium excretion (>1%). In spite of the seemingly profound damage that occurs to nephrons in ATN, tubular epithelial cells have excellent regenerative capacity. If the patient survives the maintenance stage (by conservative management or dialysis), the recovery stage follows in 1-3 weeks. Glomerular filtration rate often improves before renal tubular function is restored, so patients can develop transient polyuria (sometimes >3 L/day) with significant electrolyte wasting because tubular resorptive capacity remains impaired. During this time, patients are at high risk of developing clinically significant electrolyte imbalances, particularly hypokalemia, which can be life-threatening. Serum concentrations of magnesium, phosphorus, and calcium may also be low. Most patients recover completely, depending on the magnitude of the initial injury. (Choices A, C, and E) Hyperphosphatemia, anion gap metabolic acidosis, and volume overload occur in the maintenance stage of ATN. This patient's spontaneous diuresis and falling creatinine are more consistent with the recovery phase. (Choice D) Protein-losing nephropathies (eg, nephrotic syndrome) occur due to significant glomerular damage. Because the destruction in ATN is largely tubular, protein loss is unexpected. Patients with nephrotic syndrome typically develop progressive renal dysfunction, which would not be expected to improve after 8 days. Educational objective: Acute tubular necrosis is characterized by tubular injury due to renal ischemia or direct cytotoxicity. The course of the disease can be broken into 3 stages: initiation (initial insult), maintenance (oliguric renal failure), and recovery. During the recovery period, glomerular filtration rate improves prior to restoration of renal tubular resorptive capacity, so transient polyuria and electrolyte wasting (eg, hypokalemia) can occur.

A 38-Year-Old Man Comes to the Emergency Department Because He