Study guide
Renal System: High-Yield PANCE Study Guide
The Genitourinary/Renal system comprises roughly 5% of the current NCCPA PANCE blueprint (effective 2025), emphasizing acute kidney injury, chronic kidney disease, electrolyte/acid-base disturbances, glomerular disease, and nephrolithiasis. Master pattern-recognition of lab triads and first-line management.
Acute Kidney Injury (AKI)
- ◆Defined by KDIGO as rise in SCr >=0.3 mg/dL within 48h, >=1.5x baseline within 7 days, or urine output <0.5 mL/kg/h for 6h.
- ◆Prerenal (most common): FENa <1%, urine Na <20, BUN:Cr >20:1, bland sediment; caused by hypovolemia, HF, NSAIDs/ACEi hemodynamics. Restore perfusion.
- ◆Intrinsic ATN: FENa >2%, urine Na >40, muddy brown granular casts; from ischemia, contrast, aminoglycosides, rhabdo (check CK, myoglobin).
- ◆Acute interstitial nephritis: fever, rash, eosinophilia/eosinophiluria, WBC casts; classic triggers NSAIDs, beta-lactams, PPIs, sulfa. Stop offending drug.
- ◆Postrenal: bilateral obstruction or single functioning kidney; renal ultrasound shows hydronephrosis. Relieve obstruction (catheter/stent).
- ◆Emergent dialysis indications (AEIOU): Acidosis, Electrolytes (refractory hyperkalemia), Ingestions, Overload (pulmonary edema), Uremia (pericarditis, encephalopathy).
Chronic Kidney Disease (CKD)
- ◆Staged by eGFR (G1 >=90 to G5 <15) AND albuminuria (A1 <30, A2 30-300, A3 >300 mg/g); requires >=3 months of abnormality.
- ◆Diabetes and hypertension are the two leading causes; screen diabetics annually with urine albumin:creatinine ratio.
- ◆First-line to slow progression: ACEi or ARB (reduce proteinuria; continue even if eGFR falls below 30) PLUS an SGLT2 inhibitor (eGFR >=20). KDIGO 2024 targets standardized office systolic BP <120 mmHg when tolerated; many texts/ADA still cite <130/80.
- ◆Fourth pillar for T2D CKD with residual albuminuria despite max RAAS blockade + normal K+: add finerenone (nonsteroidal MRA, eGFR >25); GLP-1 receptor agonists also confer kidney/CV benefit.
- ◆Complications: anemia (EPO deficiency; give ESA when Hb <10 after repleting iron), CKD-mineral bone disease (high phosphate, low calcium, high PTH; give phosphate binders/calcitriol).
- ◆Manage hyperkalemia and metabolic acidosis; refer to nephrology at eGFR <30 or A3 albuminuria for transplant/dialysis planning.
Electrolyte and Acid-Base Disorders
- ◆Hyperkalemia with ECG changes (peaked T waves -> widened QRS -> sine wave): IV calcium gluconate FIRST for membrane stabilization, then insulin+glucose, albuterol; then remove K (loop diuretic, K-binder, dialysis).
- ◆Hyponatremia: assess volume status; correct <8 mEq/L per 24h to avoid osmotic demyelination. SIADH (euvolemic, low serum osm, high urine osm) treated with fluid restriction.
- ◆Hypernatremia: free water deficit; replace slowly. Diabetes insipidus - desmopressin for central, correct cause for nephrogenic (lithium, hypercalcemia).
- ◆Anion gap metabolic acidosis (MUDPILES): methanol, uremia, DKA, propylene glycol, isoniazid, lactic acidosis, ethylene glycol, salicylates.
- ◆Normal (non-gap) acidosis: diarrhea (bicarbonate loss) and renal tubular acidosis. RTA type 1 (distal, hypokalemia, alkaline urine, stones), type 4 (hyperkalemia, hypoaldosteronism/diabetes).
Glomerular Disease
- ◆Nephritic syndrome: hematuria with RBC/dysmorphic casts, HTN, mild proteinuria, oliguria. Think PSGN, IgA nephropathy, anti-GBM, ANCA vasculitis, lupus.
- ◆IgA nephropathy (Berger): gross hematuria 1-2 days after URI (synpharyngitic); most common glomerulonephritis worldwide.
- ◆PSGN: 2-3 weeks after strep pharyngitis or skin infection; low C3, positive ASO/anti-DNase B; supportive care, usually self-limited in children.
- ◆Nephrotic syndrome: proteinuria >3.5 g/day, hypoalbuminemia, edema, hyperlipidemia, lipiduria (fatty/oval casts). Minimal change disease is most common in kids (responds to steroids).
- ◆Adult nephrotic: FSGS (most common overall, HIV/obesity), membranous (anti-PLA2R, malignancy/solid tumors), diabetic nephropathy (Kimmelstiel-Wilson nodules).
Nephrolithiasis
- ◆Presents with acute severe colicky flank pain radiating to groin, hematuria, unable to find comfortable position; noncontrast CT is the gold-standard diagnostic.
- ◆Calcium oxalate stones most common (~75-80%), radiopaque; associated with hypercalciuria and low urine citrate.
- ◆Uric acid stones are radiolucent (acidic urine, gout); struvite stones from urease-producing organisms (Proteus) form staghorn calculi at alkaline pH.
- ◆Stones <5 mm usually pass spontaneously; give hydration, analgesia (NSAIDs first-line), and tamsulosin for medical expulsive therapy of distal ureteral stones.
- ◆Urgent urology/decompression if obstruction with infection (fever, pyuria), AKI, or intractable pain; prevention with increased fluid intake and thiazides for calcium stones.
Urinary Tract Infection and Related
- ◆Uncomplicated cystitis first-line: nitrofurantoin 5 days, TMP-SMX 3 days (if local resistance <20%), or fosfomycin single dose; avoid fluoroquinolones as first-line.
- ◆Pyelonephritis: fever, flank/CVA tenderness, nausea; outpatient fluoroquinolone or ceftriaxone-then-oral; admit if septic, pregnant, or vomiting.
- ◆Treat asymptomatic bacteriuria ONLY in pregnancy and before urologic procedures; do not treat in elderly or catheterized patients otherwise.
- ◆Nitrofurantoin is contraindicated in pyelonephritis (poor tissue levels) and at eGFR <30; avoid at term in pregnancy.
- ◆Recurrent/complicated UTI in men or with obstruction warrants evaluation; consider imaging and address underlying cause.