Buku Medicine

Introduction

Overview 

Quick tip: Stage 3 AKI occurs when creatinine has increased 3 fold. All patients with stage 3 AKI should be discussed with renal. 

Acute kidney injury (AKI) refers to a sudden deterioration in kidney function from a person’s baseline, which is known or presumed to have occurred within the previous 7 days.  The e-alert systems used in some hospitals which send the notices can be ‘fooled' in a number of ways so it is important to pay reference to the patient’s ‘baseline’ kidney function where previous records exist. 

AKI can be grouped into 3 stages: 

  • Stage 1: 1.5 x increase in serum creatinine from baseline 
  • Stage 2: 2 x increase in serum creatinine from baseline 
  • Stage 3: 3 x increase in serum creatinine from baseline 

 

AKI can also be staged by urine output, however this is often less helpful upon initial presentation. 

  • AKI is a heterogeneous syndrome - it is NOT a diagnosis on its own. 
  • When faced with a patient with AKI, document the STAGE and CAUSE of the AKI (see causes module
  • E.g. AKI stage 2 secondary to volume depletion (vomiting), hypotension, sepsis and contributing medications (NSAIDs, gentamicin) 
  • E.g. AKI stage 3 with unclear precipitant - ?vasculitis 

Outpatient workup

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Inpatient workup

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Causes

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Management

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Recovery

The return of urine output is often the first sign of recovery in AKI.  As urine output improves the creatinine usually continues to rise for several days before plateauing and eventually falling.  Urine volume is not helpful if the patient has non-oliguric AKI.   

  • Renal recovery can still occur months after AKI onset.   
  • In most AKI, the likelihood of recovery is dictated by their baseline renal function and the duration of their insult. 

Polyuria during recovery from AKI 

  • Polyuria is common after pre-renal and post-renal AKI 
  • During recovery, the kidneys produce copious volumes of dilute ‘poor quality’ urine 
  • Many patients need IV fluids in the early stage of post-AKI polyuria to prevent volume depletion hindering their recovery 
  • In patients who can reliably drink, it may be appropriate to let them guide their own fluid replacement according to thirst (as long as AKI continues to improve at same rate) 
  • Often patients have accumulated excess total body water and so it is appropriate to aim for a neutral or slightly negative (e.g 500-1000ml) fluid balance 
  • In general do not discharge people until urine output <3 litres as patients will struggle to drink more than this if needed. 

 

Discharge summary following admission with AKI should include;

  • Maximum stage of AKI 
  • Aetiology 
  • Treatment, including if they needed dialysis 
  • Degree of recovery at time of discharge 
  • Post-discharge monitoring e.g. do they need bloods repeated? Do they need medications restarted or avoided? 
  • When is clinic follow-up? This will be guided by renal team and will vary with degree of renal recovery prior to discharge

References

References for AKI content

https://renal.org/wp-content/uploads/2017/07/FINAL-AKI-Guideline.pdf 

https://www.thinkkidneys.nhs.uk/aki/wp-content/uploads/sites/2/2018/11/Nov-18-TK-AKI-Primary-Care-Slides-FINAL.pdf 

https://www.rcgp.org.uk/clinical-and-research/resources/toolkits/acute-kidney-injury-toolkit.aspx 

https://cks.nice.org.uk/acute-kidney-injury#!scenario 

McDonald J, McDonald R, Lieske J, et al. Risk of Acute Kidney Injury, Dialysis, and Mortality in Patients With Chronic Kidney Disease After Intravenous Contrast Material Exposure. Mayo Clin Proc. 2015;90(8):1046-1053. https://www.ncbi.nlm.nih.gov/pubmed/26250726