1. 77‐year‐old man with an increase in serum creatinine from 1.4 to 1.7 mg/dL in the past 48 hours.
   
2. 24‐year‐old man with a serum creatinine that increased from 0.7 to 1.5 mg/dL in the past 48 hours.
   
3. 32‐year‐old woman with anuria for 12 hours.
   
4. 58‐year‐old man started on renal replacement therapy 24 hours prior.
   
5. 45‐year‐old woman with urine output < 0.5 mL/kg/hr × 5 hours after exploratory laparotomy.

Acute kidney injury is diagnosed in patients based on creatinine elevation (≥ 0.3 mg/dL) from baseline over a 48‐hr period or by a period of oliguria (≤ 0.5 mL/kg/hr) over 6 hours.

Patients with stage 2 acute kidney injury have a serum creatinine that have doubled in 48 hours or have oliguria for over 12 hours.

Patients with stage 3 acute kidney injury have a serum creatinine that has tripled from baseline in 48 hours or have oliguria (≤ 0.3 mL/kg/hr) for over 24 hours or anuria for 12 hours. Patients initiated on renal replacement therapy are categorized as stage 3 also.

The only patient that does not meet the definition is option E as she has only been oliguric for under 6 hours.

Answer: E

Kellum JA . (2015) Diagnostic criteria for acute kidney injury. Critical Care Clinics , 31(4) pp. 621–632.

Ostermann M and Joanniidis M (2016) Acute kidney injury 2016: diagnosis and diagnostic work‐up. Critical Care , 20, pp. 1–13.

1. 94‐year‐old woman with a recent diagnosis of stage 3 AKI and potassium level of 5.5 mEq/L, but with a good prognosis.
   
2. 58‐year‐old man with stage 3 AKI that is resistant to diuretic administration and a potassium level of 6.2 mEq/L.
   
3. 48‐year‐old man with traumatic brain injury that is in septic shock secondary to pneumonia and anuric for 24 hours with a creatinine level of 3.5 mg/dL
   
4. 28‐year‐old woman recovering from intra‐abdominal sepsis with stage 1 AKI with improving creatinine levels.
   
5. 54‐year‐old woman with chronic kidney disease who recently underwent angiography for claudication workup and stage 1 AKI.

Approximately one third of critically ill patients will develop acute kidney injury. Of these patients, 30–70% may require renal replacement therapy. As the development of acute kidney injury is strongly associated with mortality in the critically ill, it is important to determine the etiology and tailor management promptly. While the timing of renal replacement therapy remains controversial, the initiation of therapy for diuretic‐resistant volume overload, acidosis, severe hyperkalemia, and severe uremia is agreed upon. Patients without these signs/symptoms or evidence of improving renal function do not require any form of renal replacement therapy.

The patients in options A, D, E do not meet the thresholds for any form of renal replacement therapy.

The patients in options B and C meet criteria for renal replacement therapy; however, the patient in option B could most likely tolerate intermittent hemodialysis versus the patient in option C with a traumatic brain injury who is not hemodynamically stable. Continuous renal replacement would produce less disequilibrium compared to intermittent therapy and thus less risk of having episodes of cerebral hypoperfusion.

Answer: C

KDIGO Clinical Practice Guideline for Acute Kidney Injury (2012) Kidney International Supplements, 2(1), http://www.kdigo.org/clincal_practice:guidelines/pdf/KDIGO%20AKI%20Guideline.pdf.

Tandukar S and Palevsky PM. (2019) Continuous renal replacement therapy: who, when, why, how. Chest , 155(3), pp. 626–638.

1. N‐acetylcysteine
   
2. IV sodium bicarbonate
   
3. Ascorbic acid plus saline
   
4. N‐acetylcysteine plus IV sodium bicarbonate
   
5. No additional treatment (IV saline alone)

Contrast‐induced acute kidney injury is a problem that is commonly seen in both the outpatient and inpatient setting. Many methods have been studied to counteract this phenomenon including the use of pharmacologic agents to reduce oxidative stress of the kidney to prevent the injury from occurring. Many studies have been performed to assess using ascorbic acid (scavenger of reactive oxygen species), N‐acetylcysteine (antioxidant), and sodium bicarbonate (alkalinization to prevent production of free oxygen radicals), none of which were superior to using IV saline. There are some studies that show some promise with using saline plus N‐acetylcysteine; however, a randomized control trial performed in 2018 showed no benefit with N‐acetylcysteine over placebo for preventing contrast‐induced acute kidney injury.

Answer: E

Subramaniam RM, Suarez‐Cuervo C, Wilson RF, et al. (2016) Effectiveness of prevention strategies for contrast‐induced nephropathy: a systematic review and meta‐analysis. Annals of Internal Medicine , 164(6), pp. 406–416.

Weisbord SD, Gallagher M, Jneid H, et al. (2018) Outcomes after angiography with sodium bicarbonate and acetylcysteine. New England Journal of Medicine , 378, pp. 603–614.

1. Poor glycemic control
   
2. Need for emergent re‐operation
   
3. Male sex
   
4. Cardiopulmonary bypass use and duration
   
5. Baseline renal function

Based on many observational studies, susceptibility factors (i.e. risk) have been noted across various study populations. Patient characteristics that leave patients susceptible for developing acute kidney injury in the perioperative period include dehydration, advanced age, female gender, black race, chronic kidney disease, anemia, and diabetes mellitus. Trauma, burns, major noncardiac surgery, cardiac surgery requiring cardiopulmonary bypass, need for emergent re‐operation are additional risk factors. Interestingly, male sex is a risk factor for AKI in NON‐cardiac surgery patients, but females are more likely to develop AKI if they are undergoing a cardiac surgery procedure.

Answer: C

Hobson C, Singhania G, Bihorac A . (2015) Acute kidney injury in the surgical patient. Critical Care Clinics , 31(4), pp. 705–723.

KDIGO Clinical Practice Guideline for Acute Kidney Injury (2012) Kidney International Supplements, 2(1), http://www.kdigo.org/clincal_practice:guidelines/pdf/KDIGO%20AKI%20Guideline.pdf.

1. Improve mortality
   
2. Should be started early in the development of AKI
   
3. Decrease the likelihood of requiring renal replacement therapy
   
4. Needs to be administered in high doses to be effective
   
5. Have minimal‐to‐no impact on the need for renal replacement therapy

Although furosemide has been prescribed for decades now to patients who develop acute kidney injury to try and convert them from oliguric AKI to non‐oliguric AKI, there is little‐to‐no convincing evidence that this has any impact on the need for CRRT or survival. There are conflicting reports in the literature that it may in fact reduce survival, although in meta‐analyses this effect does not seem to be borne out. There is no data to support the use of higher doses or the use of earlier administration to increase success rates. There is minimal evidence to support the routine use of furosemide in the care of patients with AKI.

Answer: E

Bove T, Belletti A, Putzu A et al. (2018) Intermittent furosemide administration in patients with or at risk for acute kidney injury: meta‐analysis of randomized trials. PLoS One , 13(4), p. e0196088

Kryzych LJ and Czempik PF . (2019) Impact of furosemide on mortality and the requirement for renal replacement therapy in acute kidney injury: a systematic review and meta‐analysis of randomized trials. Annals of Intensive Care , 9, p. 85

1. Decrease ICU mortality
   
2. Increase in‐hospital mortality
   
3. Decrease cost of managing patients with acute kidney injury
   
4. Potentially decrease hospital length of stay
   
5. Lead to an increased risk of dialysis dependence at the time of hospital discharge

For some time, there was growing evidence that early initiation of early renal replacement therapy led to improved survival. However, a recent systematic review demonstrated that there was no significant difference in mortality, ICU length of stay, hospital length of stay, or need for hemodialysis at the time of hospital discharge when early renal replacement therapy was compared to delayed initiation. In light of these facts among others, it was concluded that there was no advantage to starting early renal replacement therapy, especially as there were some patients with severe acute kidney injury that never were initiated on renal replacement therapy. Research has not been able to demonstrate a significant difference in hospital length of stay; however, early initiation of therapy may be associated with a shorter hospital stay due to the ability of some centers having the ability to discharge patients to another level of care (i.e. LTAC or rehab).

Answer: D

Gaudry S, Hajage D, Benichou N, et al. (2020) Delayed versus early initiation of renal replacement therapy for severe acute kidney injury. Lancet , 395(10235), pp. 1506–1515.

1. Abdominal CT scan
   
2. MR urography
   
3. Rectal exam
   
4. Replacement of the foley catheter
   
5. Ultrasonography of the GU tract

Replacing the foley catheter will relieve the urinary retention in addition to quantifying the amount of urine produced in the postoperative period while you are continuing your workup. A rectal examination allows you to evaluate the patient’s prostate for hypertrophy or the presence of a prostate cancer. Ultrasonography of the GU tract is a common screening modality and is highly sensitive for detecting hydronephrosis. While not the first choice in the workup of the patient, a CT scan can provide additional information regarding the anatomy of the urinary tract that is not elucidated by ultrasonography, as well as evaluating for renal calculi. MR urography is a useful modality for the investigation of obstructive uropathy in the pediatric population and would not be in the initial workup algorithm for this patient

Answer: B

Frøkiaer J and Zeidel ML. (2012) Urinary tract obstruction, in Brenner and Rector’s The Kidney , 9^th edition (editors, MW Taal, GM Chertow, PA Marsden, et al.), W.B. Saunders, Philadelphia, PA, pp. 1383–1410.

Morin CE, McBee MP, Trout AT, et al. (2018) Use of MR urography in pediatric patients. Current Urology Reports , 19(11), p. 93.

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