History Taking · Foundation · Nephrology

Acute Kidney Injury in a 56-Year-Old Woman

Practise this PLAB 2 history taking station on Lithium Toxicity. 8-minute voice AI simulation with feedback on all 3 marking domains.

Clinical scenario

You are an FY2 doctor in an acute medical unit. Ms Tolu Okeke, a 56-year-old woman with bipolar disorder, has been admitted with acute kidney injury. She has been on lithium for twelve years. Recent blood tests show elevated creatinine and elevated serum lithium levels. Please take a focused history to assess toxicity, identify precipitating factors, and discuss urgent management.

Background notes: PMH: Bipolar disorder type 1, Appendicectomy

What this station tests

  • Recognising lithium toxicity: coarse tremor, confusion, slurred speech, ataxia plus GI symptoms in a patient on lithium
  • Understanding the mechanism: dehydration from intercurrent illness reduces renal lithium clearance, causing accumulation
  • Teaching the lithium sick day rule: contact prescriber when dehydrated or unwell, as lithium levels will rise
  • Managing the patient's attachment to lithium: acknowledging its importance for bipolar stability while addressing the safety concern
  • Chronic lithium nephrotoxicity: nephrogenic diabetes insipidus and interstitial nephritis as long-term complications

How to use your 8 minutes

  • 0-1 min — Introduction: Introduce yourself, confirm identity, open question. 'What's brought you in today?'
  • 1-4 min — Systematic History: Presenting complaint detail (SOCRATES for pain, timeline, severity). Systems review. PMH, medications, allergies.
  • 4-6 min — Context and ICE: Social history (smoking, alcohol, occupation, living situation). Family history. Ideas, Concerns, Expectations.
  • 6-7 min — Summary and Plan: Summarise findings back to patient. Share differential/working diagnosis. Outline investigation and management plan.
  • 7-8 min — Closing: Safety netting with specific red flags. Arrange follow-up. Check for questions.

Consultation approach

The opening

Lithium toxicity presents with a triad of GI, neurological, and renal symptoms. The candidate must recognise the presentation, understand why it happened (usually dehydration reducing lithium clearance), and manage the patient's attachment to lithium sensitively. Ms Okeke is 56, bipolar disorder on lithium for 12 years, admitted with AKI, elevated lithium level, vomiting, confusion, and tremor. Open with: 'Ms Okeke, you have been quite unwell. Can you tell me what you remember about how this started?'

Core approach

Establish the sequence. She had a flu-like illness with diarrhoea and vomiting for several days. She became dehydrated. Dehydration reduces renal clearance of lithium, causing levels to rise into the toxic range. She continued taking her lithium during the illness (she did not know to stop or reduce it). By the time her flatmate brought her in, she was confused, tremulous, and had slurred speech.

Assess current toxicity features. GI: nausea, vomiting, diarrhoea. Neurological: coarse tremor (fine tremor is therapeutic, coarse is toxic), confusion, disorientation, ataxia, slurred speech. Renal: reduced urine output, elevated creatinine. Check for severe features: seizures (none), arrhythmias (ECG needed), coma (she is confused but conscious).

She has been struggling with medication adherence for 18 months but is deeply attached to lithium: it has kept her stable for 12 years. She is terrified of stopping it because she fears relapse into mania or depression. This emotional attachment must be handled with care.

Key concern: chronic lithium use can cause nephrogenic diabetes insipidus and chronic interstitial nephritis. Her AKI may be superimposed on chronic lithium-related kidney damage. Renal function may not fully recover.

Closing and safety netting

Immediate management: lithium is withheld (already done on admission). IV fluids for rehydration. Serial lithium levels every 6 hours until falling into therapeutic range. ECG monitoring. Renal function monitoring. If level is above 3.5 mmol/L or she is seizing, consider haemodialysis.

Address her lithium concern sensitively. 'The lithium will be restarted once your kidneys have recovered and we are confident it is safe. We may need to adjust the dose, and we will work with your psychiatrist to make sure your bipolar disorder stays well-managed.' If long-term lithium is no longer safe due to kidney damage, alternatives (valproate, quetiapine, lamotrigine) exist.

Teach the sick day rule for lithium: 'When you are ill, especially with vomiting or diarrhoea, you must contact your doctor about your lithium dose. Dehydration makes lithium levels rise dangerously.' This is the preventive message. Safety net: she will be monitored as an inpatient.

How examiners mark this station

Examiners will focus on the thoroughness and structure of your history taking for lithium toxicity. Domain 1 (Data Gathering) carries the most weight: expect marks for systematic coverage of presenting complaint, red flags, PMH, medications, social and family history. Domain 2 (Clinical Management) requires a clear differential, appropriate investigations, and a safe management plan with safety netting. Domain 3 (Interpersonal Skills) is assessed throughout: genuine exploration of ICE, active listening, empathic responses, and clear communication without jargon.

Domain 1: Data Gathering, Technical and Assessment Skills (Primary focus)

Scores well: Toxicity sequence established (illness, dehydration, accumulation). Toxicity features graded (GI, neurological, renal). Severe features screened (seizures, arrhythmias). Chronic kidney damage considered. Adherence history explored.

Costs marks: Not establishing the sequence. Not grading severity. Not checking for chronic nephrotoxicity.

Domain 2: Clinical Management Skills (Primary focus)

Scores well: Lithium withheld. IV fluids. Serial levels every 6 hours. ECG monitoring. Haemodialysis criteria known. Sick day rule taught. Psychiatry involvement for medication review.

Costs marks: Not withholding lithium. No serial levels. No ECG. Not involving psychiatry. No sick day education.

Domain 3: Interpersonal Skills (Primary focus)

Scores well: Acknowledging lithium's importance for her mental health. Reassuring about restarting when safe. Not unilaterally stopping a medication she relies on. Addressing her fear of relapse.

Costs marks: Dismissing her attachment to lithium. Permanently stopping without psychiatry input. Not addressing relapse fear.

Common examiner feedback (and how to fix it)

Did not gather sufficient information to make an adequate assessment of the patient's condition

Fix: Use a consistent framework for every history. After covering the presenting complaint, systematically move through PMH, drug history, social history, family history, and ICE. Keep a mental checklist.

Did not identify the patient's problems and/or did not develop a management plan adequately

Fix: Reserve the final 2 minutes to summarise your findings, share your working diagnosis with the patient, and outline your investigation and management plan including safety netting.

Common mistakes in this station

  1. Not understanding why the toxicity occurred. Dehydration from vomiting and diarrhoea reduced renal clearance. Candidates who say 'she took too much lithium' miss the mechanism: she took her usual dose but her kidneys could not clear it.
  2. Not teaching the sick day rule. The preventive message is: contact your prescriber when you are dehydrated or unwell. Candidates who manage the acute episode without teaching prevention allow recurrence.
  3. Telling her lithium must be stopped permanently without involving her psychiatrist. The decision to change a long-term mood stabiliser is a specialist decision. Candidates who unilaterally stop lithium risk psychiatric relapse.

Resitting PLAB 2?

If you have previously struggled with history taking stations, focus on building a consistent systematic framework that you apply to every case. Practise structuring your history into clear phases (presenting complaint, systems review, PMH, social, ICE) so that even under pressure, you cover all domains. Many resitters lose marks not on knowledge but on organisation and time management.

Example opening

Good morning/afternoon, my name is Dr [Name], I'm one of the doctors here today. Could I confirm your name and date of birth please? Thank you. So, what's brought you in to see me today?

Frequently asked questions

What is the best way to take a lithium toxicity history in PLAB 2?

Lithium toxicity presents with a triad of GI, neurological, and renal symptoms. The candidate must recognise the presentation, understand why it happened (usually dehydration reducing lithium clearance), and manage the patient's attachment to lithium sensitively. Ms Okeke is 56, bipolar disorder on lithium for 12 years, admitted with AKI, elevated lithium level, vomiting, confusion, and tremor.

Where are marks won and lost in this lithium toxicity station?

Examiners reward: Toxicity sequence established (illness, dehydration, accumulation). Toxicity features graded (GI, neurological, renal). Severe features screened (seizures, arrhythmias). Chronic kidney damage considered. Candidates are penalised for: Not establishing the sequence. Not grading severity. Not checking for chronic nephrotoxicity.

Where do candidates most often go wrong in this station?

Not understanding why the toxicity occurred. Dehydration from vomiting and diarrhoea reduced renal clearance. Candidates who say 'she took too much lithium' miss the mechanism: she took her usual dose but her kidneys could not clear it.

Can I do well in this station without real-world experience of lithium toxicity?

Structure beats experience here. Focus on understanding the mechanism: dehydration from intercurrent illness reduces renal lithium clearance, causing accumulation. Use the domain breakdown on this page to target your preparation, then practise the station aloud so your structure survives exam pressure.

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