A 32-year-old man is hospitalized with multiple fractures and internal bleeding following a motor vehicle collision. He is successfully resuscitated and taken to the operating room for fixation of a left femoral fracture. The patient's condition remains stable postoperatively, and he is transferred to the surgical floor. Blood pressure is 118/68 mm Hg and pulse is 88/min. He develops oliguria on the second day of hospitalization. Renal biopsy findings are shown in the image below. If the kidney biopsy were repeated 1 month from now, which of the following would most likely be seen?

Question

A 32-year-old man is hospitalized with multiple fractures and internal bleeding following a motor vehicle collision.  He is successfully resuscitated and taken to the operating room for fixation of a left femoral fracture.  The patient's condition remains stable postoperatively, and he is transferred to the surgical floor.  Blood pressure is 118/68 mm Hg and pulse is 88/min.  He develops oliguria on the second day of hospitalization.  Renal biopsy findings are shown in the image below.  If the kidney biopsy were repeated 1 month from now, which of the following would most likely be seen?

Quizplus · Accepted Answer

11ec160b_3a26_6a35_9249_79f159018c00_MD0001_00 This patient has ischemic acute tubular necrosis (ATN) as a result of hypotension from hemorrhage. The clinical course of ATN may be divided into the initiation, maintenance (oliguric), and recovery phases. The initiation phase corresponds with the original ischemic or toxic insult and lasts approximately 24-36 hours. During this phase, only a slight decrease in urine output is present as renal tubular cell damage begins. During the maintenance phase, tubular damage is fully established, resulting in oliguria, fluid overload, and electrolyte abnormalities (eg, hyperkalemia, metabolic acidosis). This phase usually lasts 1-2 weeks, during which the glomerular filtration rate remains well below normal with a corresponding rise in serum creatinine. Light microscopy shows tubular epithelial necrosis, sloughing of cells with denuded basement membranes, and casts containing degenerating cells and debris. The recovery phase is characterized by the re-epithelization of tubules. The glomerular filtration rate recovers relatively quickly as the tubules clear of casts and debris. However, the tubular cells recover more gradually, resulting in transient polyuria and loss of electrolytes due to impaired tubular resorption and decreased renal concentrating ability. The majority of patients eventually have complete restoration of renal function. (Choices A, B, and D) Diffuse mesangial sclerosis results in infantile nephrotic syndrome, whereas focal segmental glomerulosclerosis causes nephrotic syndrome in adolescents and adults and can be related to drug use (eg, heroin). Glomerular epithelial proliferation occurs in crescentic glomerulonephritis and diabetic nephropathy, among other diseases. These findings are not common in ATN. (Choice C) Focal interstitial fibrosis causing medullary scarring and atrophy may be seen in a small number of patients, especially when ATN is accompanied by disruption of the tubular basement membrane. It is not, however, the most common outcome of ATN. Educational objective: Acute tubular necrosis is characterized by focal tubular epithelial necrosis with denuding of the basement membrane. Most patients experience tubular re-epithelization and regain normal renal function.

A 32-Year-Old Man Is Hospitalized with Multiple Fractures and Internal