Kidney Failurex

Kidney Failure AKI Definition Based on Either: • ↑Serum creatinine • Oliguria • According to KDIGO o ↑SCr by >0.3mg/dL (26.5μmol/L) within 48hrs o ↑SCr by >1.5x baseline occurring within the prior 7 days o Urine volume <0.5mL/kg/hr for 6 hours Causes: • Pre-renal o True volume depletion o Hypotension/shock o Drugs: ACEIs, ARBs, NSAIDs, calcineurin inhibitors, aminoglycosides o Oedematous states: ↓CO in HF, splanchnic pooling and systemic vasodilation in cirrhosis • Renal o Glomerular: GN, thrombotic microangiopathy, vasculitis o Tubulointerstitial: ATN from hypoperfusion, acute interstitial nephritis  ATN causes: • Renal ischaemia: all causes of prerenal AKI, hypotension, shock, surgery, etc. • Sepsis: associated shock/hypotension • Nephrotoxins: aminoglycosides, cisplatin, radiocontrast, cidofovir • Post-renal: any obstruction Causes of AKI in Hospitalised Patients • ATN: 45% • Pre-renal: 21% • Acute superimposed on CKD: 13% mostly due to ATN and prerenal causes • Urinary obstruction: 10% (usually BPH) • GN or vasculitis: 4% • AIN: 2% • Atheroemboli: 1% AKI Patient Evaluation • EUC: for diagnosis and monitoring of AKI • FBC: some anaemia expected in AKI, disproportionate anaemia indicates myeloma or macroangiopathic haemolytic anaemia e.g. HUS or TTP • Myeloma screening • LFT: hepatorenal syndrome • Coags: sepsis or thrombotic microangiopathy • ABGs: acid-base status • Renal ultrasound: obstruction • Urine dipstick: proteinuria, haematuria, leukocytes o If haematuria: urinalysis for dysmorphic RBCs and RBC casts to investigate for GN • Urinary Na o Urine Na concentration: Low in prerenal disease: <10mEq/L, due to Na conservation  High in ATN: >40-50mEq/L due to reduced tubular function o Fractional excretion of Na: better indicator than urinary Na concentration  𝑈𝑁𝑎 × 𝑆𝐶𝑟 𝐹𝐸𝑁𝑎 = 𝑆𝑁𝑎 × 𝑈𝑐𝑟 × 100 o <1% in pre-renal o >2% in ATN GN Diagnosis • ↓Serum complement: post-infective GN, SLE, endocarditis associated GN, cryoglobulinaemia associated GN • Blood and urine cultures: post-infective GN, antistreptococcal antibodies • ANA, ENA, Ds-DNA to exclude SLE • Hepatitis screening to exclude cryoglobulinaemic nephritis and mesangiocapillary GN • ANCA to exclude vasculitis: PR3 ANCA positive granulomatosis with polyangitis and MPO ANCA positive microscopic polyangitis • Anti-GBM antibodies to rule out Goodpasture syndrome (AntiGBM disease) AKI Treatment • Fluid resuscitation if hypovolaemic (pre-renal) • Monitor urine output, fluid balance chart, daily weight for volume status  Cease nephrotoxic and non-essential medication Indications for Dialysis in AKI • Refractory Hyperkalaemia or ECG • Pulmonary oedema • Acidosis pH<7.15 • Uraemic encephalopathy • Uraemic pericarditis CKD Diagnosis • ↓GFR for >3months • If not ↓GFR o Albuminaemia: albumin to creatinine ratio (ACR) in an untimed spot urine test. ACR>30mg/g is CKD o Urinary sediment: RBC/WBC casts, dysmorphic RBC o Imaging: polycystic kidneys, hydronephrosis o Biopsy: abnormal o Kidney transplant CKD Causes • DM and HTN: 60% cases followed by GN and autosomal dominant polycystic kidney disease (ADPKD) • Comorbidities: AKI, renal stones, Nephrotoxins, family history, long-term steroid use Complications • Fluid, electrolyte, acid/base disorders o Fluid overload o Hyperkalaemia o Metabolic acidosis • CVS o HR o CHD o Systolic and diastolic HF o Uraemic pericarditis • Haematopoietic syndrome o Anaemia due to:  EPO deficiency  Iron deficiency  ↓RBC survival  ↑Hepcidin  Hyperparathyroidism Drugs o Platelet dysfunction/hypercoagulability Bone and Mineral Metabolism in CKD  • Commonly: o Phosphate retention o Low serum calcium o High PTH • Can lead to o High turnover bone disease: hyperPTism  osteitis fibrosa cystica o Low turnover bone disease: aggressive control of PTH leads to Adynamic bone disease (most common) o Osteomalacia: aluminium toxicity (rare) o Dialysis related amyloidosis: B2-microglobulin deposition in CKD patients on dialysis Neurological Complications of CKD • Uraemic encephalopathy • Dialysis disequilibrium syndrome (DDS) o Aggressive urea removal  water movement into brain  cerebral oedema o Risk factors: first dialysis treatment, high blood urea concentration prior to dialysis CKD Complications • Changing insulin requirements: ↑need early on due to insulin resistance and ↓need as GFR falls <20mL as renal clearance of insulin decreases • Uraemic pruritus • Calciphylaxis (calcific uraemic arteriolopathy): skin ischaemia and necrosis due to calcification of dermal arterioles Indications for Dialysis in CKD • Pericarditis • Progressive uraemic encephalopathy or neuropathy • Bleeding diathesis due to uraemia • Fluid overload refractory to diuretics • Metabolic disturbances • Persistent nausea/vomiting