Nephrology — 5-min cram sheet
_Built from the nephro disease index. Deck-faithful._
Buzzword → answer (the vignette reflex)
- Sub-epithelial "humps" on EM → Post-streptococcal GN (PIGN) (granular IgG/IgM/C3 in BM zone)
- Linear IgG deposits along the GBM (IF) → Goodpasture's / anti-GBM (targets α3 chain of type IV collagen)
- Mesangial IgA + C3 on IF → IgA nephropathy (Berger's)
- Anti-PLA2R antibodies → primary Membranous Nephropathy (podocyte antigen)
- LM normal, IF no deposits, EM diffuse podocyte foot-process effacement → Minimal Change Disease
- Wavy / basketweave split GBM on EM → Alport syndrome (type IV collagen mutation)
- Muddy brown granular casts → Acute Tubular Necrosis
- Flea-bitten kidney; fibrinoid necrosis + onion-skin arteriosclerosis → Malignant hypertension (BP >200/120)
- Tubular "thyroidisation" (dilated tubules, colloid casts) → Chronic pyelonephritis
- Dipstick +ve for blood but NO RBCs on microscopy → Rhabdomyolysis (myoglobin) / haemoglobinuria
- Eosinophiluria + interstitial eosinophil infiltrate sparing glomeruli → Drug-induced AIN
- "Beaded" appearance on angiography (mid-to-distal artery) → Fibromuscular dysplasia (typical age 35, female)
- Ring sign + clubbed calyces on IVP; bilateral, no cortical loss → Papillary necrosis (analgesic nephropathy)
- Saturnine gout + disproportionate hyperuricaemia → Lead nephropathy (welders, battery workers)
Urinary / biopsy finding → diagnosis
| Finding | Diagnosis |
| Sub-epithelial "humps" (EM); granular IgG/IgM/C3 (IF) | PIGN |
| Mesangial IgA + C3 (IF); mesangial hypercellularity | IgA nephropathy |
| Linear IgG along GBM (IF); crescents | Goodpasture's / anti-GBM |
| Crescents (parietal proliferation + fibrin), GBM rupture on EM | Rapidly Progressive (crescentic) GN |
| Thickened GBM on silver stain (mimics membranous) | Lupus nephritis Class V |
| LM normal, IF no deposits, EM podocyte effacement | Minimal Change Disease |
| Segmental sclerosis starting at juxtamedullary glomeruli; IgM + C3 in hyaline | FSGS |
| Thickened GBM (LM); sub-epithelial deposits (EM); granular IgG + C3; anti-PLA2R | Membranous Nephropathy |
| Type 2 = dense deposit disease, intramembranous "ribbon" deposits; ↓ C3 | MPGN |
| Wavy / basketweave split GBM (EM) | Alport syndrome |
| Muddy brown granular casts + renal tubular epithelial cell casts | ATN |
| RBC casts | Glomerular bleeding — IgA nephropathy, lupus nephritis, Goodpasture's, vasculitis |
| WBC casts | Pyelonephritis / interstitial inflammation / parenchymal infection |
| Fatty casts / oval fat bodies | Nephrotic syndrome |
| Waxy casts | Advanced kidney disease + chronic kidney failure |
| Hyaline casts | Dehydration, exercise, diuretics (few normal) |
| Granular casts (nonspecific) | Many disorders, especially ATN |
| Eosinophiluria + WBC casts | Drug-induced AIN |
| Tubular thyroidisation; polar scars (reflux) | Chronic pyelonephritis |
| Hyaline arteriolosclerosis; leather-like bilateral granular surface | Benign nephrosclerosis |
| Ghost glomeruli; bilateral symmetrical contracted granular kidneys, thin cortex | Chronic glomerulonephritis |
| Multiple filling defects on urography | Urothelial carcinoma (TCC) — vs stones |
| Sterile pyuria | TB (Mycobacterium tuberculosis) |
Criteria / staging / scores at a glance
- KDIGO CKD diagnosis — GFR <60 mL/min/1.73 m² OR ≥1 marker of kidney damage (albuminuria ACR >30 mg/g or >3 mg/mmol; sediment / tubular / histological / structural abnormality; transplant Hx), present >3 months.
- ADPKD US criteria (positive FHx) — <30 y: 2 cysts (uni/bilateral); 30–59 y: 2 cysts in each kidney; ≥60 y: 4 cysts in each kidney (stricter with age).
- RIFLE — Risk (sCr ×1.5 or ≥0.3 mg/dL; UO <0.5 mL/kg/h ×6 h) · Injury (sCr ×2; UO <0.5 ×12 h) · Failure (sCr ×3, or ≥0.5 mg/dL if baseline >4.0; UO <0.3 ×24 h or anuria ×12 h) · Loss (complete loss >4 wk) · ESRD.
- AKIN — Stages 1–3 = first 3 RIFLE grades (drops Loss/ESRD); any patient on RRT = automatically Stage 3.
- KDIGO AKI — St1: sCr 1.5–1.9× baseline OR ≥26.5 µmol/L (0.3 mg/dL) rise, UO <0.5 mL/kg/h for 6–12 h · St2: sCr 2–2.9× · St3: sCr 3× OR start RRT, anuria ≥12 h. <18 y: eGFR <35.
- KDIGO GFR categories — G1 ≥90 · G2 60–89 · G3a 45–59 · G3b 30–44 · G4 15–29 · G5 <15 (ESRD → dialysis). ACR (mg/mmol) A1 <3 · A2 3–30 · A3 >30.
- eGFR equations — CKD-EPI (most used, more accurate at high GFR) vs MDRD (older, less accurate at high GFR); markers = serum creatinine + cystatin C. Measured-GFR gold standard = inulin clearance.
- Lupus nephritis Classes I–VI — I minimal mesangial · II mesangial proliferative · III focal (<50% glomeruli) · IV diffuse (≥50%) + crescents (most severe) · V membranous (sub-epithelial, thickened GBM on silver stain) · VI advanced sclerosis. Deposits: III+IV sub-endothelial, I–V mesangial, V sub-epithelial.
- RPGN types by IF — I linear (anti-GBM / Goodpasture's) · II granular immune-complex (SLE, post-infective) · III pauci-immune (Wegener's granulomatosis, PAN).
- VUR grades 1–5 — 1 ureter only · 2 up to renal pelvis, no dilatation · 3 mild dilatation of ureter + PCS · 4 moderate dilatation, blunted fornices, preserved papillary impressions · 5 severe dilatation, loss of fornices + papillary impressions (Grades 4+5 → surgery).
- Pre-renal vs intrinsic AKI (urine chemistry) — SG >1.020 vs <1.010 · U osm >500 vs <350 · U Na <10 vs >20 · FENa <1% vs >1% · BUN:Cr >20:1 vs <20:1 · Urea:Cr >40:1 vs <40:1. FENa = [(U Na × serum Cr) / (U Cr × serum Na)] × 100.
- Urinary casts (7 types) — fatty = nephrotic · granular = nonspecific, esp. ATN · hyaline = dehydration/exercise/diuretics · RBC = glomerular bleeding · renal tubular epithelial cell = tubular necrosis/transplant rejection · WBC = pyelonephritis/interstitial · waxy = advanced/chronic renal failure.
Discriminators that decide questions
- Nephritic vs nephrotic — Nephritic: oliguria, haematuria, hypertension, mild proteinuria (<3 g/day), mild oedema, RBC casts. Nephrotic: proteinuria >3.5 g/day + serum albumin <3.5 g/dL + generalised oedema (± hyperlipidaemia, lipiduria, oval fat bodies). MPGN = mixed nephrotic + nephritic.
- Complement pattern — ↓ C3, normal C4 = alternative pathway (PIGN, MPGN type 2) · normal C3 + normal C4 (IgA nephropathy) · ↓ C3, ↓ C4 = classical pathway (lupus nephritis; MPGN types 1 & 3).
- PIGN vs IgA nephropathy — PIGN: haematuria 1–4 weeks after Group A strep, ↓ C3, sub-epithelial humps, only 1–2% → CKD. IgA: synpharyngitic haematuria 1–2 days after URTI, normal complement, mesangial IgA + C3, 50% → CKD.
- Pre-renal vs established ATN — Pre-renal: FENa <1%, U Na <10, U osm >500, BUN:Cr >20:1 → give fluid challenge (250 mL crystalloid). Established ATN: FENa >1%, U Na >20, U osm <350, muddy brown casts → DO NOT give fluid, supportive only.
- MCD vs FSGS — MCD: steroid-responsive, LM normal, commonest nephrotic in children. FSGS: often steroid-resistant, segmental sclerosis from juxtamedullary zone (deep biopsy needed), almost all → CKD.