A 29-year-old woman at 32 weeks gestation presents to the obstetric assessment unit with headache and right upper quadrant pain. She has no significant past medical history. Blood pressure is 168/112 mmHg. Blood tests show: haemoglobin 102 g/L, platelets 88 × 10^9/L, ALT 245 U/L, AST 312 U/L, bilirubin 34 μmol/L, creatinine 145 μmol/L (booking creatinine was 68 μmol/L), LDH 680 U/L. Urinalysis shows protein 3+. Peripheral blood film shows schistocytes. What is the most appropriate immediate management?

Commence IV labetalol, IV magnesium sulphate, and arrange immediate delivery

Commence IV magnesium sulphate and plan delivery within 24-48 hours

Commence plasma exchange for thrombotic thrombocytopenic purpura

Commence high-dose corticosteroids for HELLP syndrome

Transfuse platelets and arrange delivery once platelets >100 × 10^9/L

A 38-year-old man with chronic kidney disease stage 5 (eGFR 10 mL/min/1.73m²) secondary to focal segmental glomerulosclerosis is being prepared for renal replacement therapy. He has preserved urine output of approximately 1500 mL per day. He works full-time as a teacher and wishes to minimize time spent on dialysis. Blood tests show: haemoglobin 108 g/L, potassium 5.1 mmol/L, phosphate 1.72 mmol/L, albumin 36 g/L. He has good manual dexterity and lives with his partner. Which renal replacement modality would be most appropriate to offer first?

Automated peritoneal dialysis (APD)

Continuous ambulatory peritoneal dialysis (CAPD)

In-centre haemodialysis three times weekly

Pre-emptive renal transplantation

A 48-year-old woman with no significant past medical history presents to the emergency department with a 6-hour history of severe right loin pain. CT KUB confirms a 5 mm stone at the right pelviureteric junction with mild hydronephrosis. She is afebrile. Blood tests show: white cells 9.2 × 10^9/L, CRP 8 mg/L, creatinine 78 μmol/L. Urinalysis shows blood 3+, leucocytes 1+, nitrites negative. She has been given adequate analgesia with diclofenac and morphine. What is the most appropriate next step in her management?

Discharge with analgesia, alpha-blocker, and follow-up in stone clinic

Admit for IV antibiotics due to obstructive pyelonephritis

Arrange urgent ureteroscopy and stone extraction within 48 hours

Insert percutaneous nephrostomy for decompression

Arrange extracorporeal shock wave lithotripsy (ESWL) within one week

A 52-year-old woman presents to the emergency department with confusion and agitation. Her husband reports she has had watery diarrhoea for 5 days. She has a history of bipolar disorder treated with lithium for 15 years. Blood tests show: sodium 128 mmol/L, potassium 3.2 mmol/L, creatinine 245 μmol/L (baseline 85 μmol/L), lithium level 2.8 mmol/L (therapeutic range 0.6-1.0). ECG shows sinus tachycardia at 105 bpm. What is the most appropriate immediate management?

Stop lithium, give IV 0.9% saline, and arrange urgent haemodialysis

Stop lithium, give IV 0.9% saline, and recheck lithium level in 12 hours

Continue lithium, correct dehydration, and arrange gastroenterology review

Stop lithium, give hypertonic saline for hyponatraemia, then arrange dialysis

Stop lithium, give IV fluids, and start haemofiltration

A 67-year-old man with chronic kidney disease stage 3a (eGFR 52 mL/min/1.73m²) secondary to diabetic nephropathy attends for annual review. He takes metformin, gliclazide, ramipril, atorvastatin, and aspirin. Blood tests show: HbA1c 64 mmol/mol, creatinine 128 μmol/L (stable from previous), potassium 5.4 mmol/L, bicarbonate 19 mmol/L. Urine albumin:creatinine ratio is 45 mg/mmol. Blood pressure is 138/82 mmHg. What is the most appropriate modification to his management?

Add SGLT2 inhibitor for renoprotection

Increase ramipril dose to maximize renoprotection

Stop ramipril due to hyperkalaemia and worsening renal function

Add sodium bicarbonate supplementation for metabolic acidosis

Add spironolactone for additional proteinuria reduction

A 34-year-old previously healthy woman presents with oliguria and peripheral oedema. Blood tests show: creatinine 320 μmol/L (baseline 72 μmol/L two weeks ago), urea 22.4 mmol/L, albumin 28 g/L. Urinalysis shows protein 4+, blood 2+, and no leucocytes or nitrites. Urine protein:creatinine ratio is 520 mg/mmol. Renal biopsy shows crescentic glomerulonephritis. Serology shows: ANCA negative, anti-GBM negative, ANA 1:640 (speckled pattern), anti-dsDNA positive, C3 0.42 g/L (normal 0.75-1.65), C4 0.08 g/L (normal 0.14-0.54). What is the most likely diagnosis?

Anti-GBM disease (Goodpasture syndrome)

Post-streptococcal glomerulonephritis

A 56-year-old woman with chronic kidney disease stage 4 (eGFR 20 mL/min/1.73m²) secondary to IgA nephropathy presents for routine review. She reports increasing fatigue. Blood tests show: haemoglobin 95 g/L, ferritin 280 μg/L, transferrin saturation 28%, PTH 18.5 pmol/L (normal 1.6-6.9), corrected calcium 2.12 mmol/L, phosphate 1.85 mmol/L, 25-hydroxyvitamin D 32 nmol/L. What is the most appropriate initial management of her secondary hyperparathyroidism?

Start colecalciferol 20,000 units weekly

Start alfacalcidol 250 nanograms daily

Start calcium carbonate 1.25 g three times daily with meals

A 28-year-old man presents to the emergency department with sudden onset severe left-sided loin pain radiating to the groin. He has vomited twice and appears distressed. He has a history of inflammatory bowel disease (Crohn's disease) and has undergone two small bowel resections. CT KUB shows a 7 mm calculus at the left vesicoureteric junction with moderate hydronephrosis. Blood tests show: creatinine 88 μmol/L, calcium 2.35 mmol/L, uric acid 380 μmol/L. What is the most likely stone composition in this patient?

Struvite (magnesium ammonium phosphate)

Acute kidney injury: High-Yield Medicine (Core Systems) Lessons

Quick Overview

Acute Kidney Injury (AKI) is a sudden decline in renal function occurring within hours-days, affecting 15-20% of hospital admissions. NICE NG148 emphasizes early detection via creatinine rise or reduced urine output, with prompt categorization into pre-renal (60-70%), intrinsic (25-40%), or post-renal (5-10%) causes to guide management and prevent progression to chronic kidney disease.

Core Facts & Concepts

KDIGO Staging Criteria (defines AKI severity):

Stage	Creatinine Rise	Urine Output
1	≥26.5 μmol/L in 48h OR 1.5-1.9× baseline	<0.5 mL/kg/h for 6-12h
2	2.0-2.9× baseline	<0.5 mL/kg/h for ≥12h
3	≥3× baseline OR ≥354 μmol/L OR RRT initiated	<0.3 mL/kg/h for ≥24h OR anuria ≥12h

Classification by Cause:

Pre-renal (70%): Hypoperfusion → hypovolemia, sepsis, cardiac failure, renal artery stenosis
- Urine Na⁺ <20 mmol/L, FENa <1%, urine osmolality >500 mOsm/kg
Intrinsic (25%): Tubular (ATN), glomerular, interstitial, vascular damage
- Urine Na⁺ >40 mmol/L, FENa >2%, muddy brown casts (ATN)
Post-renal (5%): Obstruction → stones, BPH, malignancy, retroperitoneal fibrosis
- Bilateral obstruction OR unilateral with solitary kidney required

![Ultrasound showing bilateral hydronephrosis with dilated renal pelvis](Image: bilateral hydronephrosis ultrasound)

📊 Critical Numbers:

Baseline creatinine: use lowest value in past 3-12 months
Nephrotoxins to stop: NSAIDs, ACE-i/ARBs, aminoglycosides, diuretics (if hypovolemic)
Target MAP >65-70 mmHg for renal perfusion

Problem-Solving Approach

NICE NG148 Diagnostic Algorithm:

Confirm AKI: Check creatinine rise/urine output against KDIGO criteria
Assess volume status: JVP, mucous membranes, skin turgor, postural BP, fluid balance charts
Urinalysis: Dipstick (blood/protein suggests glomerular), microscopy (casts, cells)
Identify cause:
- Pre-renal: Trial fluid challenge (250-500 mL crystalloid over 15 min); response suggests pre-renal
- Intrinsic: Check eosinophils (AIN), CK (rhabdomyolysis), immunology (vasculitis)
- Post-renal: Urgent USS within 24h if cause unclear or anuria
Stop nephrotoxins immediately (NICE NG148 recommendation)
Monitor: Daily U&Es, fluid balance, weight, urine output (catheterize if Stage 3)

Figure 1: Urine microscopy showing muddy brown granular casts

🚩 Red Flags for Urgent Nephrology Referral:

Stage 3 AKI or rapidly rising creatinine
K⁺ >6.5 mmol/L despite treatment
Pulmonary edema unresponsive to diuretics
Suspected glomerulonephritis/vasculitis (hematuria + proteinuria)
pH <7.2 (metabolic acidosis)

Analysis Framework

Differentiating AKI Causes:

Feature	Pre-renal	Intrinsic (ATN)	Post-renal
Urine Na⁺	<20 mmol/L	>40 mmol/L	Variable
FENa	<1%	>2%	Variable
Urine osmolality	>500 mOsm/kg	<350 mOsm/kg	Variable
Urine sediment	Bland/hyaline casts	Muddy brown/epithelial casts	Normal
Response to fluids	Improves	No improvement	No improvement
USS findings	Normal	Normal/echogenic	Hydronephrosis (if bilateral)

📌 Remember: RIFLE - Risk, Injury, Failure, Loss, ESKD (older AKI classification, now superseded by KDIGO)

Visual Aid

Key Points Summary

✓ KDIGO Stage 1: Creatinine ≥26.5 μmol/L rise in 48h OR 1.5× baseline; Stage 3 requires RRT consideration
✓ Pre-renal (70%): Low urine Na⁺ (<20), FENa <1%, responds to fluid challenge within 2-4h
✓ Stop nephrotoxins immediately: NSAIDs, ACE-i/ARBs, gentamicin, metformin (NICE NG148)
✓ Urgent USS within 24h if cause unclear, anuria, or suspected obstruction
✓ Refer nephrology urgently for Stage 3, K⁺ >6.5 mmol/L, pH <7.2, suspected GN/vasculitis
✓ Muddy brown casts = ATN (intrinsic); hydronephrosis = post-renal obstruction
✓ Monitor daily: U&Es, fluid balance, weight; catheterize for accurate output in Stage 3

⚠️ Warning: Diuretics worsen pre-renal AKI-assess volume status first before administering

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