In a 45-year-old woman with oliguria after massive hemorrhage and multiple contusions despite adequate hydration (prerenal acute kidney injury), which urine index is expected?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: February 10, 2026 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Prerenal AKI: Expected Urine Indices

In a 45-year-old woman with oliguria following massive hemorrhage and multiple contusions (prerenal AKI), the expected finding is a urine plasma creatinine ratio >40. 1

Understanding Prerenal AKI Physiology

In prerenal AKI from hemorrhage and hypovolemia, the kidneys respond physiologically by maximally conserving sodium and water while concentrating the urine. 1 This adaptive response creates a characteristic pattern of urine indices that reflects intact tubular function attempting to restore intravascular volume. 2

Expected Urine Indices in Prerenal AKI

Urine Sodium

  • Urine sodium should be <20 mEq/L (NOT >40 mEq/L) in prerenal AKI 1, 2
  • The kidneys avidly reabsorb sodium to preserve intravascular volume 1
  • Urine sodium >40 mEq/L suggests intrinsic renal disease (acute tubular necrosis) where tubular function is impaired 2

Specific Gravity

  • Specific gravity should be >1.020 (NOT <1.018) in prerenal AKI 1
  • High specific gravity reflects concentrated urine from intact tubular concentrating ability 1
  • Specific gravity <1.018 or isosthenuric urine (1.010) indicates loss of concentrating ability, characteristic of intrinsic renal disease 3

Urine to Plasma Creatinine Ratio

  • Urine to plasma creatinine ratio >40 is the CORRECT expected finding 1, 2
  • This elevated ratio reflects avid tubular reabsorption of water and sodium while creatinine continues to be excreted 1
  • In acute tubular necrosis, this ratio falls to <20 due to impaired tubular function 1

Additional Supportive Indices

While not asked in the question, other indices that support prerenal AKI include:

  • Fractional excretion of sodium (FENa) <1% indicates prerenal AKI 1, 2
  • **Renal failure index (RFI) <1** shows high specificity (>85%) for prerenal AKI 2
  • BUN:Creatinine ratio >20:1 suggests prerenal azotemia 1

Important Clinical Caveats

The traditional paradigm of "prerenal" versus "intrinsic" AKI is increasingly questioned. 4 Recent evidence demonstrates that:

  • Urinary biomarkers of injury (KIM-1, cystatin C, IL-18) are elevated even in "prerenal" AKI that recovers within 48 hours 5
  • This suggests prerenal AKI represents a milder form of actual kidney injury rather than purely functional impairment 5
  • AKI exists on a continuum of injury severity rather than discrete categories 4

Confounding factors that limit urine indices accuracy: 2, 4

  • Loop diuretics invalidate FENa (use FEUrea instead) 2
  • Chronic kidney disease may alter baseline concentrating ability 2
  • However, recent data show UNa, USG, and RFI maintain diagnostic value despite these confounders 2

In this clinical scenario of massive hemorrhage with "adequate hydration," the patient may be transitioning from prerenal to intrinsic AKI if resuscitation was delayed or inadequate. 6 The KDIGO criteria define AKI by creatinine rise ≥0.3 mg/dL within 48 hours or urine output <0.5 mL/kg/h for 6 hours. 7, 8

References

1
Research

Acute kidney injury: a guide to diagnosis and management.

American family physician, 2012

3
Guideline

Acute Intrinsic Renal Failure (Acute Tubular Necrosis)

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

4
Research

Urinalysis and pre-renal acute kidney injury: time to move on.

Critical care (London, England), 2013

6
Guideline

Fluid Administration in Rhabdomyolysis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

7
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

8
Guideline

Diagnóstico y Estadificación de Lesión Renal Aguda

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

Related Questions

Is this patient's acute kidney injury prerenal in nature?
What is the most likely cause of acute kidney injury in a 76‑year‑old woman with hypertension and diabetes on valsartan who had severe vomiting and diarrhea, resulting in a creatinine rise from 0.6 to 1.6 mg/dL, low BUN/creatinine ratio, urine sodium 60 mEq/L, low specific gravity, and urine osmolality 220 mOsm/kg?
Which of the following statements about pre‑renal and post‑renal acute kidney injury are correct? a. Urinary sodium concentration in pre‑renal acute kidney injury is above 40 mmol/L; b. Erythrocyte casts are present in the urine sediment of post‑renal acute kidney injury; c. The urea‑to‑creatinine ratio exceeds 50 in pre‑renal acute kidney injury; d. Urine osmolality is higher in post‑renal than in pre‑renal acute kidney injury; e. Urine sediment may be bland (without casts or cells) in pre‑renal acute kidney injury.
What is the management approach for acute kidney injury (AKI) with accompanying foot swelling and impaired renal function?
In an 18‑year‑old woman with severe volume depletion and pre‑renal acute kidney injury, which laboratory finding is most consistent: BUN/creatinine ratio 13, fractional excretion of sodium 2.3 %, urine osmolality 300 mOsm/kg, urine sodium 13 mEq/L, or fractional excretion of urea 40 %?
In a patient already on a maximally tolerated dose of atorvastatin, how should I choose the rosuvastatin dose to add based on LDL‑C and triglyceride levels?
Can an otherwise healthy adult with mild, non‑specific liver enzyme elevation safely use Liv 52 (herbal liver support), and what dose and monitoring are recommended?
In preterm infants with severe respiratory failure, what are the recommended glucocorticoid regimens (including drug choice, dose, and duration) to balance therapeutic benefit with neurodevelopmental safety?
In preterm infants with severe respiratory failure who remain ventilator‑dependent, what postnatal age is safest to initiate glucocorticoid therapy?
Patient with prior pancreatitis and cholecystectomy presents with epigastric pain radiating to the right upper quadrant and back, previously markedly elevated serum lipase now normal, and normal C‑reactive protein and white blood cell count. What are the likely differential diagnoses and appropriate management plan?
How can arterial PCO₂ be lowered in a mechanically ventilated patient with chronic obstructive pulmonary disease who is on volume‑controlled ventilation?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question