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Acute Kidney Injury

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Urology

🔎 Always investigate for acute kidney injury (AKI) by checking serum creatinine (and comparing with baseline), urine dip for nephritis, and assessing fluid status. Most cases are supportive, but some need urgent intervention (e.g., catheter, stent, dialysis).

🚑 General Management Summary (Hyperkalaemia First!)

Emergency Management of AKI
ABC, O₂ if hypoxic, IV access, ECG monitoring. 📉 Treat hyperkalaemia ≥ 6.0 mmol/L immediately. 🌡️ Treat systemic infection or urosepsis with IV antibiotics. Send bloods: FBC, U&E, Ca/P/ALP, CRP, Lactate. Do ECG, CXR, VBG/ABG. Prerenal: Fluids, sepsis treatment, stop BP-lowering drugs (ACEI, ARB, CCB). Consider inotropes if shocked. Renal: Stop nephrotoxins (ACEI/ARB/NSAID/Gent). Order ANCA/ANA/anti-GBM if nephritis suspected. Renal referral. Postrenal: Catheterize. If oliguria/anuria, urgent renal USS (<12h). Consider dialysis if: – Refractory hyperkalaemia – Pulmonary oedema – Severe uraemia (encephalopathy, pericarditis) – Severe acidosis unresponsive to fluids/bicarb.

Emergency Management of AKI

ABC, O₂ if hypoxic, IV access, ECG monitoring.
📉 Treat hyperkalaemia ≥ 6.0 mmol/L immediately.
🌡️ Treat systemic infection or urosepsis with IV antibiotics.
Send bloods: FBC, U&E, Ca/P/ALP, CRP, Lactate. Do ECG, CXR, VBG/ABG.
Prerenal: Fluids, sepsis treatment, stop BP-lowering drugs (ACEI, ARB, CCB). Consider inotropes if shocked.
Renal: Stop nephrotoxins (ACEI/ARB/NSAID/Gent). Order ANCA/ANA/anti-GBM if nephritis suspected. Renal referral.
Postrenal: Catheterize. If oliguria/anuria, urgent renal USS (<12h).
Consider dialysis if: – Refractory hyperkalaemia – Pulmonary oedema – Severe uraemia (encephalopathy, pericarditis) – Severe acidosis unresponsive to fluids/bicarb.

📖 About AKI

AKI has replaced the older term “acute renal failure.”
Defined as a sudden fall in renal function → ↑ urea/creatinine, ↓ urine output.
Often reversible if identified and treated early.
eGFR is unreliable in acute illness — use creatinine and urine output instead.

📊 KDIGO Definition & Staging

Stage	Criteria
1	Creatinine 1.5–1.9× baseline OR ↑ ≥26 µmol/L in 48h OR urine <0.5 ml/kg/hr for 6–12h
2	Creatinine 2–2.9× baseline OR urine <0.5 ml/kg/hr ≥12h
3	Creatinine 3× baseline OR RRT started OR anuria ≥12h

⚡ Renal Functions Affected

Water/electrolyte control
Excretion of toxins & drugs
Acid–base regulation
BP control (RAAS)
EPO & Vitamin D activation

🧾 Causes of AKI

Site	Examples	Actions
Prerenal	Hypovolaemia (bleeding, burns, sepsis), hypotension, ACEI/ARB/NSAIDs, PPIs	Fluids, sepsis control, stop offending drugs, vasopressors if needed
Renal (Intrinsic)	ATN (45%), RPGN, GN, vasculitis, interstitial nephritis, HUS/TTP	Nephrology input, send ANCA/ANA/anti-GBM, stop nephrotoxins, consider biopsy
Postrenal	Stones, strictures, malignancy, prostate obstruction	Catheterize, USS (<12h), consider stent/nephrostomy, urology input

🔬 Prerenal vs Intrinsic Renal (Urine Features)

Urine SG: Prerenal > 1.020 vs. Renal < 1.010
Urine Osmolality: Prerenal > 500 vs. Renal < 350 mOsm/kg
Urinary Na⁺: Prerenal < 20 vs. Renal > 40 mmol/L

🧍 Clinical Presentation

Malaise, lethargy, anorexia, nausea, vomiting
Oliguria/anuria OR polyuria (if concentrating defect)
Confusion, delirium, seizures, coma in severe cases
Fluid overload → pulmonary oedema, raised JVP
Skin pallor, pruritus; bruising (platelet dysfunction)
Uraemic pericarditis → friction rub, tamponade

🧪 Investigations

Bloods: U&E (↑ urea/creatinine, ↑ K⁺), Ca/P/ALP, CRP, FBC, film
Urine: Dipstick (protein/haematuria), microscopy (casts)
Serology: ANCA, ANA, Anti-GBM, complements
Imaging: Renal USS (exclude obstruction), CXR (pulm oedema), ECG (K⁺)
Special: Myeloma screen (high calcium/ESR), HIV, biopsy if unclear

🧪 Selected Targeted Tests

Nephritis: ANCA, ANA
Acidosis: ABG (HCO₃⁻ <19 mmol/L)
Rhabdomyolysis: CK
SBP <110 + sepsis: Lactate
ENT bleed + renal: Anti-GBM
High Ca²⁺ + ESR: Myeloma screen

💊 Management (With Renal/Urology Input)

NEWS monitoring, fluid balance chart, daily U&E
Prerenal: Hydrate (0.9% saline 1L over 2–4h, reassess). Pressors if shocked
Renal: Stop nephrotoxins, treat vasculitis if confirmed, immunosuppression if needed
Postrenal: Relieve obstruction (catheter/stent/nephrostomy)
Acidosis: Consider IV bicarbonate (1.26%)
Hyperkalaemia: Calcium gluconate + insulin/dextrose + salbutamol neb
Dialysis indications (AEIOU): – Acidosis (pH < 7.2) – Electrolytes (K⁺ refractory) – Ingestions (toxin) – Overload (pulm oedema) – Uraemia (encephalopathy, pericarditis)

🧾 Haemofiltration

Preferred in unstable patients in ITU.
Early discussion with renal + intensive care is essential.

📚 References

NICE NG148: Acute Kidney Injury (2019)

Cases — Acute Kidney Injury (AKI)

Case 1 — Pre-Renal (Hypovolaemia) 🩸: A 72-year-old man admitted with profuse diarrhoea and vomiting presents with hypotension and oliguria. Urea:creatinine ratio raised. Diagnosis: AKI due to volume depletion. Management: IV fluids, electrolyte correction, stop nephrotoxic drugs (e.g., NSAIDs, ACEi).
Case 2 — Pre-Renal (Heart Failure) ❤️: A 68-year-old woman with decompensated LV systolic failure presents with worsening breathlessness and reduced urine output. JVP elevated, bilateral crackles. Diagnosis: Pre-renal AKI due to low cardiac output. Management: Diuretics for pulmonary oedema, optimise heart failure therapy, careful fluid balance.
Case 3 — Intrinsic Renal (ATN from Contrast Nephropathy) ⚡: A 65-year-old man undergoes PCI with IV contrast. Two days later, he develops oliguria and rising creatinine. Urine microscopy: muddy brown casts. Diagnosis: AKI due to acute tubular necrosis from contrast. Management: Stop nephrotoxins, IV hydration, consider renal replacement therapy if severe.
Case 4 — Intrinsic Renal (Acute Interstitial Nephritis) 💊: A 54-year-old woman treated with antibiotics for UTI presents with rash, fever, and AKI. Urine: eosinophils present. Diagnosis: Drug-induced acute interstitial nephritis. Management: Stop offending drug; supportive care ± corticosteroids if severe.
Case 5 — Post-Renal (Obstructive) 🚧: An 80-year-old man with known BPH presents with anuria, lower abdominal pain, and bilateral hydronephrosis on ultrasound. Diagnosis: Post-renal AKI due to bladder outlet obstruction. Management: Immediate bladder catheterisation; urology referral; long-term BPH management.

Teaching Commentary 🧠

AKI is classified into: - Pre-renal (hypoperfusion: dehydration, heart failure, sepsis), - Intrinsic (tubular, glomerular, interstitial, vascular), - Post-renal (obstruction). Always look for reversible causes: hypovolaemia, sepsis, drugs, obstruction. Initial management is ABCDE, stop nephrotoxins, check fluid status, catheterise, and correct potassium. Early nephrology input if severe or prolonged.

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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