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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- First compare with baseline: acute rise = AKI; persistent abnormality for >=3 months = CKD; both can coexist
- Assess danger: hyperkalaemia, acidosis, pulmonary oedema, uraemic symptoms, rapidly rising creatinine, oliguria/anuria, obstruction
- Initial work-up: urinalysis/microscopy, ACR/PCR, electrolytes/bicarbonate, medication review, BP/volume status, and renal ultrasound when obstruction or chronicity is unclear
- CKD staging requires both eGFR category and albuminuria category; albuminuria is a major risk marker
- Avoid nephrotoxins, adjust drug doses, control BP/diabetes, and refer when eGFR is low, albuminuria high, active sediment, rapid decline, or complications occur
Approach to the Presentation
The MCC CKD and AKI objectives both apply to abnormal renal function. Do not treat creatinine as an isolated number: interpret it against baseline, muscle mass, volume status, medications, urine findings, and complications. The core exam move is to decide whether the patient needs emergency treatment, urgent nephrology/urology, or structured outpatient CKD risk reduction.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Acute kidney injury | must-not-miss | Recent rise in creatinine, oliguria, dehydration, sepsis, hypotension, nephrotoxins, contrast, obstruction | Creatinine trend, urine output, urinalysis, electrolytes, bladder scan/ultrasound |
| Obstructive uropathy | must-not-miss | LUTS, retention, anuria, hydronephrosis, pelvic malignancy, stones, solitary kidney | Bladder scan and renal ultrasound/CT |
| Rapidly progressive glomerulonephritis | must-not-miss | Hematuria, proteinuria, casts, hypertension, oedema, systemic vasculitis/lupus, pulmonary haemorrhage | Urine microscopy, serology, urgent biopsy |
| Hyperkalaemic renal failure | must-not-miss | Weakness, arrhythmia, ECG changes, ACEi/ARB, spironolactone, CKD/AKI | Potassium + ECG |
| Diabetic kidney disease | common | Longstanding diabetes, albuminuria, gradual eGFR decline, retinopathy, hypertension | ACR, eGFR trend, retinal/vascular context |
| Hypertensive/vascular CKD | common | Longstanding hypertension, vascular disease, small kidneys, bland urine sediment | BP history, urine ACR, renal ultrasound |
| Medication-related creatinine rise | common | ACEi/ARB expected small rise, TMP, NSAIDs, diuretics, PPIs, lithium, aminoglycosides | Medication timeline, repeat creatinine, urinalysis |
| Polycystic kidney disease | less common | Family history, hypertension, enlarged kidneys, hematuria, stones, cyst infections | Renal ultrasound |
| Laboratory/physiologic artefact | less common | High muscle mass, creatine use, dehydration, assay interference, trimethoprim inhibiting secretion | Repeat test, cystatin C if needed, clinical correlation |
Red Flags & Key History
Symptoms
Oliguria/anuria, dyspnoea, confusion, chest pain, severe weakness — urgent complication
Hematuria, rash, haemoptysis, arthralgia — glomerulonephritis/vasculitis
Lower urinary tract symptoms, retention, pelvic malignancy, stone symptoms — obstruction
NSAID, ACEi/ARB, diuretic, lithium, contrast, aminoglycoside, PPI exposure
Diabetes, hypertension, cardiovascular disease, family history of ESRD
Signs
Pulmonary oedema or severe volume overload
Severe hypertension or hypertensive emergency
Distended bladder
Peripheral oedema, pallor, pruritus, uraemic frost rarely
Approach to Investigation
First-line
Repeat creatinine/eGFR and compare baselineDetermine AKI vs CKD vs AKI-on-CKD; review prior labs
Electrolytes, bicarbonate, calcium/phosphate, CBCIdentify hyperkalaemia, acidosis, CKD mineral bone disease, anaemia
Urinalysis with microscopy and ACR/PCRActive sediment/proteinuria changes diagnosis and urgency
Medication and dose reviewRenally cleared drugs and nephrotoxins; sick-day considerations
Second-line
Renal ultrasoundHydronephrosis, kidney size, cystic disease, chronicity clues
Serology / myeloma screenIf active sediment, proteinuria, systemic disease, unexplained CKD, anaemia/hypercalcaemia
ECGIf potassium elevated or renal failure severe
Specialist
Nephrology referralLow eGFR, rapid decline, high albuminuria, active sediment, refractory hypertension, electrolyte/acidosis/anaemia complications
Urology referralObstruction, hydronephrosis, retention, stones, suspected malignancy
Management Principles
KDIGO 2024 CKD guideline + Canadian Society of Nephrology detection/referral guidance1
If acute or unstable
- Treat AKI cause and complications immediately
- Stop nephrotoxins, adjust doses, manage hyperkalaemia/acidosis/overload
- Relieve obstruction urgently when present
2
If CKD
- Stage by eGFR and albuminuria; monitor trend and complications
- Control BP, diabetes, cardiovascular risk, smoking, and albuminuria
- Use ACEi/ARB/SGLT2 inhibitors where indicated and safe with monitoring
3
Patient counselling
- Explain sick-day medication holds when appropriate
- Avoid NSAIDs and dehydration
- Plan immunizations, renal dosing, and nephrology referral thresholds
Complications & Pitfalls
- Baseline matters: A “mild” creatinine rise may be severe AKI in a low-muscle patient.
- Creatinine is delayed: Do not wait for large rises when urine output and potassium are worsening.
- Albuminuria matters: eGFR alone underestimates risk.
- ACEi/ARB nuance: A small early creatinine rise can be expected; large rises suggest renal artery stenosis, hypovolaemia, or other pathology.
- Obstruction is reversible: Check bladder and ultrasound when suspected.
MCCQE1 Exam Tips
- 1Ask: AKI, CKD, or AKI-on-CKD?
- 2Active sediment = glomerular disease until proven otherwise
- 3Anuria or hydronephrosis = obstruction pathway
- 4Hyperkalaemia with ECG changes is treated before the cause is fully worked up
- 5CKD staging requires eGFR plus albuminuria
- 6SGLT2/ACEi/ARB kidney protection is common, but monitor potassium and creatinine
Put your reading into practice
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