FNP nephrology: CKD management, AKI recognition, and electrolyte disorders

CKD definition (KDIGO): Kidney abnormalities present for >3 months, defined by eGFR <60 mL/min/1.73m² or markers of kidney damage (albuminuria ≥30 mg/24h or ACR ≥30 mg/g). Staging by eGFR: G1 ≥90 (normal eGFR, damage markers), G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 <15 (kidney failure).

Albuminuria staging: A1 (normal to mildly increased: <30 mg/g ACR), A2 (moderately increased: 30–300 mg/g), A3 (severely increased: >300 mg/g). Higher albuminuria + lower eGFR = higher combined risk of CKD progression.

FNP primary care CKD management:

• BP control: target <130/80 mmHg; ACE inhibitor or ARB first-line (renoprotective, reduce albuminuria)
• SGLT2 inhibitor (dapagliflozin, empagliflozin): now recommended for CKD with albuminuria ≥200 mg/g OR T2DM + CKD — renoprotective independent of glucose effect (CREDENCE, DAPA-CKD trials)
• Avoid nephrotoxins: NSAIDs, aminoglycosides, IV contrast (gadolinium caution in GFR <30), metformin eGFR <30
• Anaemia of CKD: Iron deficiency first (ferritin <100 or TSAT <20%) — treat before ESA. ESA only if Hgb <10 and iron replete; target 10–11.5 g/dL (higher targets increase CV risk)
• Hyperphosphataemia: dietary phosphorus restriction, phosphate binders (calcium acetate, sevelamer)
• Metabolic acidosis: sodium bicarbonate if serum bicarb <22 mEq/L (slows CKD progression per clinical trials)

Nephrology referral criteria: eGFR <30, rapid decline (>5 mL/min/year or >25% within 12 months), heavy proteinuria (>500 mg/g), unexplained AKI, secondary causes (glomerulonephritis, vasculitis), CKD G4 for transplant/dialysis preparation.

Hyperkalaemia (K+ >5.5 mEq/L): Common in CKD, heart failure, ACE inhibitor/ARB use, diabetes, aldosterone deficiency. Mild (5.5–6.0) — dietary restriction, medication review. Moderate (6.0–6.5 with ECG changes: peaked T waves, prolonged PR) — patiromer or sodium zirconium cyclosilicate (novel oral binders; not kayexalate first-line). Severe (>6.5 or ECG: widened QRS, sine wave) = emergency: IV calcium gluconate (membrane stabilisation), insulin + dextrose (shift K+ intracellular), sodium bicarbonate, albuterol nebulisation, dialysis if refractory.

Hyponatraemia (Na+ <135 mEq/L): Most common electrolyte disorder. Volume status assessment is key: hypovolaemic (dehydration, diuretics) → isotonic saline; euvolaemic (SIADH, hypothyroidism, adrenal insufficiency) → fluid restriction ± tolvaptan for severe/refractory; hypervolaemic (HF, cirrhosis, nephrotic) → fluid restriction + diuresis. Correction rate: ≤8–10 mEq/L per 24 hours to avoid osmotic demyelination syndrome (central pontine myelinolysis).

Uncomplicated UTI in women: Dysuria, frequency, urgency — no fever, no systemic symptoms. Diagnosis: urinalysis with ≥10 WBCs/HPF or positive leukocyte esterase/nitrite. Culture not required for uncomplicated UTI. First-line treatments: nitrofurantoin × 5 days (avoid in eGFR <30), trimethoprim-sulfamethoxazole DS × 3 days (if local resistance <20%), fosfomycin 3 g × 1 dose. Avoid fluoroquinolones for uncomplicated UTI (reserve for complicated).

Pyelonephritis: Fever (≥38°C), flank/CVA tenderness, nausea/vomiting, sometimes with UTI symptoms. Urine culture required. Obtain blood cultures if severe systemic signs. Outpatient: oral fluoroquinolone × 7 days (if susceptible) or trimethoprim-sulfamethoxazole × 14 days. Inpatient criteria: severe illness, inability to tolerate oral medications, complicated infection, or pregnancy.

Asymptomatic bacteriuria: Screen and treat ONLY in: pregnant women (screening with culture at 12–16 weeks gestation, treat if positive) and patients scheduled for urologic procedures with mucosal bleeding. Do NOT routinely treat asymptomatic bacteriuria in elderly, diabetic, catheterised, or other patients — increases antibiotic resistance without clinical benefit.