Acute Kidney Injury Following Gastroenteritis — Free SCA Practice Case
Acute Kidney Injury following Gastroenteritis
Station Timer
Golden Minute
Initial Introduction
•Introduce yourself
•Ask an open question — "How can I help you today?"
•Listen — don't interrupt
•Catch early cues
Data Gathering
History, ICE & Diagnosis
Clinical Management
Diagnosis, Plan & Decisions
Safety Net
Follow-up & Close
Materials for Candidate
Please review before starting the consultation
Full Name
Susan Clarke
Age
62 years
Consultation Type
TelephoneAge
62 (DOB: 14/03/1964)
Reason for Encounter
"You have urgently called this patient back. Her routine chronic disease monitoring bloods (taken yesterday) show a sudden, severe decline in renal function."
Medical Records
- ●PMH: Type 2 Diabetes, Hypertension.
- ●Medications: Ramipril 10mg OD, Metformin 1g BD, Dapagliflozin 10mg OD.
- ●Allergies: NKDA.
Recent Notes
- ●Yesterday: Attended HCA clinic for routine annual diabetes bloods. Patient mentioned to the HCA she had been unwell with a stomach bug but "didn't want to miss her appointment."
- ●Lab Results (Processed today): Creatinine: 240 µmol/L (Baseline 6 months ago: 85 µmol/L).
- ●eGFR: 21 ml/min (Baseline: 68 ml/min).
- ●Potassium: 5.1 mmol/L. Urea: 18 mmol/L.
- ●Lab Alert: Acute Kidney Injury (AKI) Stage 2. Urgent clinical review required.
Patient Script
For the friend playing the patient role
Character Overview: You are Susan, a 62-year-old retired bank clerk. You are a "model patient." You take your health very seriously and pride yourself on never missing a dose of your medication. Over the last four days, you have been battling a severe bout of gastroenteritis (norovirus). You had terrible diarrhea and vomiting and couldn't keep any food or water down for about 48 hours. However, because you are terrified of your diabetes getting out of control, you forced yourself to swallow your Ramipril, Metformin, and Dapagliflozin every single day with tiny sips of water, even when you were vomiting. You are finally starting to feel a bit better today. The sickness stopped yesterday, and you are sipping weak tea and eating dry toast. You are extremely surprised the doctor is calling you urgently. You assume there must be a mistake, as you feel you are "over the worst of it." You do not understand how a stomach bug can affect your kidneys. You will not volunteer exactly how much urine you are passing, your dizziness, or the fact that you forced your pills down unless the doctor specifically asks about your hydration, your symptoms, or takes a strict medication audit.
ICE — Ideas, Concerns, Expectations
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Ideas: You have no idea what could be wrong with your kidneys. You assume the stomach bug is just a stomach bug and cannot see how it could affect anything else. If pressed, you might say: "I just thought it was a bad stomach bug — food poisoning or norovirus. I don't understand what that's got to do with my kidneys."
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Concerns: Your biggest worry is your diabetes spiralling out of control. You are also frightened by the idea that something serious might be wrong that you didn't know about — you thought you were doing everything right. If the doctor explores your fears: "Honestly, my biggest worry has always been the diabetes. My mum lost her sight from it, so I'm terrified of letting it get away from me. And now you're saying my kidneys are affected — I didn't even know that was possible."
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Expectations: You want reassurance that you haven't permanently damaged your kidneys and a clear plan for what to do next. You want to know whether this is going to get better. "I just want to know if this is going to be okay. Tell me what I need to do and I'll do it — I'm not one to mess about with my health."
Consultation Flow & Responses:
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The Opening:
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If the doctor asks an open question or states the bloods are abnormal: "Oh dear. Are you sure, Doctor? I feel completely wiped out, but I thought that was just because I've had that awful stomach bug that's going around. I'm actually feeling a bit better today."
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Data Gathering (The Layers):
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Layer 1: The Infection & Hydration Status (The Trigger):
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If asked about the sickness/bug: "It was awful. Diarrhea and vomiting for 48 hours straight. I couldn't keep a single thing down. But it stopped yesterday morning. I'm managing weak tea and toast today."
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Layer 2: Renal Output & Perfusion (Safety Screen):
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If asked about passing urine: "Now that you mention it, I haven't been to the toilet much at all. Maybe once yesterday, and it was very dark. I suppose I'm just empty."
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If asked about dizziness/feeling faint: "Yes, when I stood up to answer the phone I went very lightheaded. I had to hold onto the wall for a second."
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Layer 3: The Medication Audit (The Clinical Trap):
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If asked if you have been taking your medication: Proudly. "Oh yes, Doctor. I never miss my pills. Even when I was vomiting, I made sure I forced them down with a sip of water. I didn't want my sugars going crazy while I was sick."
If Asked — Medical History and Medications
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If asked about diabetes / how long she has had it: "I was diagnosed about eight years ago. They said it was the Type 2 kind. I've been on the Metformin ever since, and then they added the Dapagliflozin about two years ago because my HbA1c was creeping up. I've been very careful with my diet — I don't touch sugary things."
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If asked about blood pressure / hypertension: "Yes, I've been on the Ramipril for about five years. They started me on it because of my blood pressure and the diabetes — the doctor said it protects the kidneys, which is ironic now. My blood pressure has been fine on it."
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If asked about Metformin specifically — dose, side effects: "I take 1000mg twice a day, morning and evening with food. I've never had any trouble with it, no stomach problems normally. I take it like clockwork."
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If asked about Dapagliflozin specifically: "That's the newer one they added. I take it in the morning. The doctor said it helps with the diabetes and the kidneys. I did notice I was going to the toilet more often when I first started it, but I got used to it."
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If asked about Ramipril specifically: "I take 10mg every morning. Never had any problems with it. No cough or anything like that."
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If asked whether anyone has ever explained 'sick day rules': "Sick day rules? No, nobody has ever mentioned anything like that to me. I've always just assumed you keep taking your tablets no matter what — that's what I've always done."
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If asked about allergies: "No, no allergies to anything that I know of."
Social History and Lifestyle Impact
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You live alone in a bungalow since your husband Gerald passed away three years ago. Your daughter Karen lives about twenty minutes away and has been checking in by phone but hasn't visited because she didn't want to catch the bug. You have been managing on your own during this illness.
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If asked about how you've been coping / the impact: "It's been miserable, to be honest. I've barely left the bedroom for four days. I couldn't even make it to the kitchen to get water — I was using a glass I kept by the bed. Karen's been ringing every day but I told her not to come over in case she caught it. I'm normally very independent — I do my own shopping, I go to my exercise class on Wednesdays — but this has really knocked me for six."
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If asked about alcohol / smoking: "I don't smoke — never have. I might have a small glass of wine at the weekend, but nothing this week obviously."
If Asked — Associated Symptoms
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If asked about blood in the urine: "No, nothing like that. It was just very dark, almost brown, but no blood that I could see."
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If asked about pain in the back or flanks / kidney area: "No, I haven't had any pain in my back or sides. Just the stomach cramps from the bug."
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If asked about swelling in the ankles or legs: "No, my ankles look normal. If anything I feel dried out rather than swollen."
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If asked about shortness of breath: "No more than usual — I do get a bit puffed going up stairs but that's been the same for years. Nothing worse this week."
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If asked about chest pain or palpitations: "No, nothing like that at all."
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If asked about confusion or drowsiness: "I've been a bit muddled — I forgot what day it was yesterday. But I think that's just because I've been in bed and not eating properly."
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If asked about muscle cramps or twitching: "I have had a few cramps in my calves, actually. I put it down to being dehydrated."
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If asked about nausea currently: "No, the nausea has settled. I managed a cup of tea and some toast this morning without any trouble."
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If asked about fever or temperature: "I did feel feverish the first couple of days — hot and cold, shivery. But that's gone now."
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If asked about appetite: "It's coming back slowly. I managed the toast this morning and I'm thinking about trying some soup later."
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If asked about rash or skin changes: "No, nothing like that."
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If asked about recent changes to medications or new medications: "No, nothing new. I've been on the same three tablets for a while now."
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If asked about over-the-counter medications / ibuprofen / NSAIDs: "No, I haven't taken anything else. I thought about taking some Ibuprofen for the stomach cramps but I didn't have any in the house, so I just stuck it out."
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If asked about previous kidney problems: "No, I've never been told there was a problem with my kidneys before. The doctor always said the Ramipril was protecting them."
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If asked about thirst: "Absolutely parched. I feel like I can't drink enough now that I can keep things down. My mouth and lips have been so dry."
Negotiation & Collaborative Management Plan:
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If the Doctor tells you to go straight to A&E without explaining why:
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Reaction: Panicked and resistant. "A&E?! But the vomiting has stopped! I can't sit in a waiting room for 10 hours, I'm exhausted. What on earth is wrong with me?"
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If the Doctor explains the pills have damaged the kidneys (Blame vs. Education):
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Reaction (If blamed): "But you prescribed them! No one ever told me I shouldn't take them if I had a stomach bug!"
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Reaction (If explained empathetically): "So because I was dehydrated, the blood pressure pills actually stopped my kidneys from filtering properly? And the diabetes pills can build up? I thought I was doing the right thing by taking them."
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If the Doctor instructs you to stop the Ramipril, Metformin, and Dapagliflozin:
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Reaction: Anxious. "Stop them completely? But won't my blood pressure go through the roof? And what about my diabetes? Is it safe to just stop them cold turkey?"
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If the Doctor sets a plan to push fluids and re-test bloods in 48 hours:
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Reaction: "Okay, I understand. I will stop all three tablets right now. I have a big jug of water next to me, I will aim to drink 2 litres today. I'll come back to the surgery on Friday for another blood test."
Mark Scheme
Domain 1: Data Gathering and Diagnosis
Domain 2: Clinical Management and Medical Complexity
Domain 3: Relating to Others
Clinical Learning Points
Recognising and Staging AKI in Primary Care
The blood results in this case represent a significant clinical emergency requiring immediate, structured action.
- ●AKI Staging: AKI is staged 1–3 based on the rise in creatinine from baseline. A doubling of creatinine (or a rise of ≥26.5 µmol/L within 48 hours) constitutes AKI Stage 2. Susan's creatinine of 240 µmol/L against a baseline of 85 µmol/L represents a near-tripling — this is unambiguous Stage 2 AKI and demands same-day action.
- ●eGFR as a Functional Marker: An eGFR of 21 ml/min places Susan in the CKD Stage 4 range acutely. While eGFR formulae are unreliable in rapidly changing renal function, the trend is what matters: a drop from 68 to 21 ml/min confirms severe, abrupt impairment.
- ●Borderline Hyperkalaemia: K+ 5.1 mmol/L in the context of AKI Stage 2 and ongoing RAAS inhibition is not trivially "borderline." As renal clearance falls further, potassium rises — this result must drive immediate cessation of Ramipril and mandatory same-day recheck of electrolytes.
The Triple Nephrotoxic Hit: Why Susan's AKI Was Predictable
This case demonstrates the convergence of three simultaneous insults on renal perfusion and function.
- ●Hypovolaemia (the driver): Four days of vomiting and diarrhoea, combined with markedly reduced fluid intake, produced severe intravascular volume depletion — the single most common precipitant of pre-renal AKI.
- ●Ramipril (the pressure failure): ACE inhibitors dilate the efferent arteriole. In a well-hydrated patient, this intraglomerular pressure reduction is renoprotective. In a volume-depleted patient, it causes intraglomerular pressure to collapse — the kidney literally cannot filter. This is the mechanism behind pre-renal AKI from RAAS inhibition.
- ●Dapagliflozin (the volume drain): SGLT2 inhibitors drive obligate osmotic diuresis — glucose-forced urinary fluid loss continues regardless of dehydration status. This worsens the hypovolaemia and directly amplifies the Ramipril-mediated filtration failure.
- ●The Near-Miss Triple Whammy: Susan considered taking ibuprofen for her stomach cramps but did not have any at home. Had she taken it, the addition of an NSAID — which constricts the afferent arteriole, reducing blood flow into the glomerulus — would have created the classic ACEi + NSAID + dehydration triple whammy, with a high probability of AKI Stage 3 and dialysis-level impairment. This is worth articulating explicitly to the patient as a future safety point.
The SGLT2 Inhibitor Emergency: Euglycaemic DKA
Candidates frequently fail to identify the acute emergency that Dapagliflozin continuation during starvation and dehydration may have already triggered.
- ●The Pathophysiology: SGLT2 inhibitors force renal glucose excretion regardless of blood glucose levels. During starvation or vomiting, glycogen stores deplete and insulin levels fall. The body switches to ketogenesis. Because the SGLT2i is continuously excreting glucose in the urine, blood glucose levels appear deceptively normal (typically <14 mmol/L) — concealing severe underlying ketoacidosis.
- ●The Clinical Trap: A normal capillary blood glucose does not exclude DKA in a patient on an SGLT2 inhibitor. Do not be falsely reassured.
- ●The Mandatory Action: Any patient on an SGLT2i who presents with vomiting, dehydration, or reduced oral intake must have capillary blood ketones checked urgently, or be referred to SDEC/Ambulatory Care for a venous blood gas (VBG) to assess ketones and pH. A pH <7.3 or ketones >3 mmol/L in this context is euglycaemic DKA until proven otherwise.
- ●Symptoms to Screen For: Nausea, abdominal pain, confusion, and Kussmaul breathing (deep, rapid respiration) in an SGLT2i patient warrant immediate escalation regardless of blood glucose.
Sick Day Rules — The SADMANs: Mechanism, Not Just Memory
In the exam, identifying which medications to stop is the minimum requirement. Explaining why — clearly and to the patient — is what separates a pass from a clear pass.
Drugs that cause or accelerate AKI (haemodynamic toxins):
- ●ACE inhibitors / ARBs (Ramipril): Dilate the efferent arteriole, reducing intraglomerular filtration pressure. Renoprotective at normal volumes; dangerous during hypovolaemia.
- ●SGLT2 inhibitors (Dapagliflozin): Drive osmotic diuresis, worsening dehydration and reducing renal perfusion; additionally risk euglycaemic DKA during starvation.
- ●NSAIDs: Constrict the afferent arteriole, reducing renal blood flow. Contraindicated in any AKI or dehydration state.
- ●Diuretics: Directly exacerbate intravascular volume depletion.
Drugs that accumulate because of AKI (clearance failures):
- ●Metformin: Does not cause AKI, but is entirely renally cleared. In AKI, it accumulates to toxic levels, inhibiting hepatic lactate metabolism and causing life-threatening lactic acidosis — presenting with abdominal pain, hyperventilation, and cardiovascular collapse.
- ●Sulphonylureas (e.g., Gliclazide): Accumulate during renal impairment, causing severe and prolonged hypoglycaemia, particularly dangerous in a vomiting patient who cannot eat to correct it.
The practical rule to give the patient: If you have vomiting and/or diarrhoea and cannot keep fluids down, stop the SADMAN drugs the same day and restart only once you have been eating and drinking normally for 24–48 hours and a blood test confirms your kidneys have recovered.
Triage Decision: SDEC vs. Community Management
Risk stratification must be verbalised explicitly in the exam. Use this framework:
Refer for Same-Day Emergency Care (SDEC) / Ambulatory Care when:
- ●Oliguria/anuria: Urine output <0.5 ml/kg/hour, or effectively absent (as in Susan's case — passed urine once in 24 hours, dark).
- ●Haemodynamic compromise: Postural hypotension, tachycardia, or inability to tolerate oral fluids.
- ●SGLT2i exposure with starvation: Ketone/VBG assessment is required and cannot be done in the community.
- ●K+ >5.5 mmol/L: Requires cardiac monitoring and urgent management.
- ●Confusion, drowsiness, or new neurological symptoms: Possible uraemic encephalopathy or lactic acidosis.
Community management is acceptable only when all of the following are met:
- ●Vomiting and diarrhoea have completely resolved.
- ●The patient is actively tolerating and retaining adequate oral fluids (target ≥2–3 litres/day).
- ●Urine output is recovering (passing normal amounts of clear urine).
- ●The patient has capacity, understands the plan fully, and has social support available.
- ●Mandatory: Repeat U&E arranged within 24–48 hours to confirm creatinine is trending down.
In Susan's case, the oliguria, postural hypotension, SGLT2i exposure, and social isolation make SDEC the appropriate gold-standard disposition — though a well-structured community plan with same-day daughter involvement, aggressive rehydration targets, and 24-hour repeat bloods represents the minimum safe alternative.
Glucose Monitoring After Stopping Both Antidiabetic Agents
Stopping Metformin and Dapagliflozin simultaneously removes all pharmacological glucose control.
- ●Susan has T2DM managed with two agents. Abrupt cessation — necessary and correct — creates real risk of symptomatic hyperglycaemia, particularly as she recovers and resumes eating.
- ●Advise her to monitor her blood glucose at least twice daily (morning and evening) while both agents are withheld, and to contact the surgery if readings exceed 15 mmol/L.
- ●If she does not have a glucometer at home, this further strengthens the case for SDEC-based monitoring.
- ●Do not assume that because she is unwell and not eating, her glucose will remain controlled — her endogenous counter-regulatory response to illness (cortisol, glucagon) will be driving glucose up.
Safe Medication Restart: The Clinical Milestones
A common follow-up question is: "When can I start taking my pills again?" Do not advise restart based on symptom resolution alone.
Two milestones must both be met before any SADMAN drug is restarted:
- ●Clinical euvolaemia: The patient has been eating and drinking normally for at least 24–48 hours, is producing normal urine output, and has no postural symptoms.
- ●Biochemical resolution: A repeat U&E confirms that creatinine and eGFR have returned to the patient's individual baseline (or plateaued at a stable new baseline acceptable to the clinician).
Drug-specific nuances:
- ●Ramipril: Restarting during incomplete renal recovery risks precipitating a secondary AKI. Confirm biochemical resolution first.
- ●Metformin: Must not be restarted until eGFR is confirmed >30 ml/min/1.73m² — and ideally back to baseline. This is an absolute threshold per NICE and MHRA guidance.
- ●Dapagliflozin: Fluid repletion alone is insufficient. The patient must have resumed a normal carbohydrate diet for at least 24 hours before restarting, to replenish glycogen stores and eliminate the euglycaemic DKA risk.
Safety Netting: Specific Red Flags for Escalation
Generic safety netting ("call if you feel worse") is insufficient in AKI. Provide actionable, specific criteria.
Call 999 or go immediately to A&E if:
- ●No urine passed for 8 or more hours.
- ●Vomiting resumes and she cannot keep fluids down.
- ●She develops confusion, drowsiness, or cannot be roused normally.
- ●She develops rapid, deep breathing (possible lactic acidosis or DKA).
- ●She develops chest pain or palpitations (possible hyperkalaemia-related arrhythmia).
- ●She feels significantly worse in any way.
Planned follow-up: Repeat U&E within 24–48 hours (not 72 hours — the trajectory must be confirmed promptly). Clear instructions on who to contact for the result and what the plan is if creatinine is not recovering.
Common Candidate Mistakes in This Station
- ●Stopping only Ramipril: The single most common prescribing error. Leaving Metformin running in AKI Stage 2 is a critical safety failure — lactic acidosis risk is real and life-threatening.
- ●Missing Dapagliflozin as an SGLT2 inhibitor: Candidates who don't recognise the drug class fail to screen for euglycaemic DKA — the most dangerous acute complication in this case.
- ●Vague disposition: Saying "go to A&E" without a clinical handover, or keeping the patient home without structured rehydration targets and a 24-hour blood test, both represent unsafe management.
- ●Reassuring on glucose: Telling Susan her glucose "will be fine" because she's not eating, while stopping both antidiabetic agents, is incorrect — counter-regulatory hormones during illness drive hyperglycaemia.
- ●Blaming the patient: Susan did everything she believed was correct. Any implication that she was at fault for taking her medications — when she was never told the sick day rules — damages the consultation and is clinically inaccurate. The iatrogenic gap belongs to the system, not the patient.
- ●Forgetting the medication restart plan: Closing the consultation without addressing when and how the withheld medications will be reviewed and restarted leaves the management incomplete.