A 38-year-old male suffered two gunshot wounds to the abdomen and was admitted to the ICU after an exploratory laparotomy with small bowel resection, sigmoid colon resection, and one intraabdominal drain placement. Postoperatively, the patient is extubated in the ICU without complications. On postoperative day # 1, he acutely develops decreasing urine output, rising creatinine, and drain output with moderate serous output. The ICU team suspects Acute Kidney Injury. They obtain a fractional excretion of urine sodium, which is between 1% to 2%, and a bedside renal ultrasound demonstrates a normal collecting duct system.
What is the BEST next step?A. Continue to monitor and discuss fluid balance
Correct Answer: B
Early diagnosis of urinary tract obstruction or ureteral injury is important and should be corrected as soon as possible, as delay in diagnosis could lead to kidney injury. All patients with AKI should have a workup for urinary tract obstruction. Ultrasound is the preferred imaging test for this diagnosis. It is important to recognize this patient’s injury and the moderate to high drain serous output with an acute decrease in urine output. This patient had a gunshot wound to the abdomen involving the sigmoid colon, which also should hint the reader to a missed ureteral injury during the abdominal exploration as they are in close proximity. A negative ultrasound has 98% negative predictive value. It is great at ruling out a chronic and acute obstruction. However, it has a false positive rate of 26%. The positive predictive is only 70%. Although this patient’s bedside ultrasound was negative for dilated collecting duct system, you cannot rule out a ureteral injury and must have a high index of suspicion. A urinoma may not be obvious in this case because there is a drain in place draining the serous fluid. If the urinoma does not build up to compress the collecting system, then it is unlikely to see a dilated collecting duct in this acute setting. The next most best step is to send the drain output for creatinine levels and notify the surgical team.