# Situation: A 66-year-old man weighing 70 kg has coronary artery disease and takes aspirin and clopidogrel after a coronary stent was placed last year. He is brought to the emergency department after vomiting bright red blood twice and passing a black, tarry stool. His blood pressure is 88/54 mmHg and heart rate 122 beats/min; he is awake and anxious. His serum creatinine on arrival is 1.0 mg/dL (88 µmol/L). On day 2 in the intensive care unit, his creatinine is 2.1 mg/dL (186 µmol/L). His urine output over the last 8 hours was 22, 20, 18, 17, 15, 14, 12 and 12 mL/h. Using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria, which stage of acute kidney injury (AKI) does he have?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=630129  
> language: ko  
> subject: Nursing Practice V — Care of Clients with Maladaptive Patterns of Behavior; Care of Clients with Life-Threatening Conditions, Acute Multi-Organ Problems, High Acuity and Emergency Situations

## 문제

Situation: A 66-year-old man weighing 70 kg has coronary artery disease and takes aspirin and clopidogrel after a coronary stent was placed last year. He is brought to the emergency department after vomiting bright red blood twice and passing a black, tarry stool. His blood pressure is 88/54 mmHg and heart rate 122 beats/min; he is awake and anxious. His serum creatinine on arrival is 1.0 mg/dL (88 µmol/L).

On day 2 in the intensive care unit, his creatinine is 2.1 mg/dL (186 µmol/L). His urine output over the last 8 hours was 22, 20, 18, 17, 15, 14, 12 and 12 mL/h. Using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria, which stage of acute kidney injury (AKI) does he have?

## 보기

1. Stage 3, based on his urine output
2. Stage 1, based on his urine output
3. Stage 2, based on his creatinine rise **✔ 정답**
4. Stage 1, based on his creatinine rise

**정답: 3**

## 해설

Creatinine 2.1 ÷ 1.0 = 2.1 times baseline, which is stage 2 (2.0–2.9 times). His urine output totals 130 mL in 8 hours, about 0.23 mL/kg/h; below 0.5 mL/kg/h for 6–12 hours is stage 1, and the stage 3 rule of below 0.3 mL/kg/h requires 24 hours or more. KDIGO uses the higher stage from either criterion, so he is stage 2.

## 심화 해설

KDIGO AKI staging: creatinine versus urine output

This patient’s acute kidney injury is staged by applying the KDIGO criteria to two separate signals: the rise in serum creatinine and the fall in urine output. The two criteria do not always point to the same stage, and the rule is to assign the higher stage when there is a discrepancy.

His creatinine rose from 1.0 to 2.1 mg/dL, which is 2.1 times his baseline. In the KDIGO framework, a creatinine increase of 2.0–2.9 times baseline defines stage 2. A rise of 1.5–1.9 times would be stage 1, and a rise of 3.0 times or more, or an absolute increase to 4.0 mg/dL or higher, or initiation of renal replacement therapy, would be stage 3.

The urine output data require a weight-based calculation. Over the last 8 hours, his total urine output was 130 mL. For a 70 kg patient, that is 130 ÷ 8 ÷ 70, approximately 0.23 mL/kg/h. Urine output below 0.5 mL/kg/h for 6 hours or more meets the threshold for stage 1 by urine output. The stage 3 urine output criterion is stricter: less than 0.3 mL/kg/h for 24 hours or more, or anuria for 12 hours or more. Because this patient’s oliguria has been documented for only 8 hours, the urine output criterion does not yet support stage 3.

| KDIGO criterion | Stage 1 | Stage 2 | Stage 3 |
| --- | --- | --- | --- |
| Serum creatinine | 1.5–1.9 × baseline or increase ≥0.3 mg/dL | 2.0–2.9 × baseline | ≥3.0 × baseline, or creatinine ≥4.0 mg/dL, or RRT |
| Urine output |

## 임상 시나리오

KDIGO AKI Staging: Creatinine vs Urine OutputAssign the higher stage when the two criteria disagree
Calculate the creatinine ratio by dividing current creatinine by baseline. A rise of 2.0–2.9x is Stage 2; 1.5–1.9x is Stage 1; ≥3.0x or creatinine ≥4.0 mg/dL or RRT initiation is Stage 3.

Convert urine output to mL/kg/h. Less than 0.5 mL/kg/h for 6–12 h is Stage 1; for ≥12 h is Stage 2. Less than 0.3 mL/kg/h for ≥24 h or anuria for ≥12 h is Stage 3.

CautionDo not stage by urine output alone when the creatinine criterion yields a higher stage. KDIGO mandates using the higher stage from either criterion. A short period of severe oliguria does not equal Stage 3 unless the duration threshold is met.

## 핵심 개념

- **KDIGO AKI staging** — Kidney Disease: Improving Global Outcomes criteria that stage acute kidney injury using the worse of serum creatinine rise or urine output decline.
- **Oliguria** — Urine output below 0.5 mL/kg/h; duration determines AKI stage (6–12 h Stage 1, ≥12 h Stage 2).
- **Anuria** — Urine output below 0.3 mL/kg/h for ≥24 hours or no urine for ≥12 hours, meeting Stage 3 AKI criteria.
- **Baseline creatinine** — The patient's pre-illness serum creatinine (1.0 mg/dL here), used as the denominator for staging creatinine rise.
- **Renal replacement therapy (RRT)** — Dialysis or hemofiltration; initiation of RRT automatically places AKI in Stage 3 regardless of other values.

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