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Chronic Kidney Disease (CKD)

Definition

  • Longstanding and progressive loss of kidney function
  • Not reversible (as in AKI)
  • Are 5 stages of renal insufficiency, defined by eGFR: CKD is generally stage 3 onwards
    • 1 – damage with normal or slight increased GFR > 90 mL/min/1.73m)
    • 2 – Mild reduction in GFR (60-89 mL/min/1.73m)
      • For stage 1 and 2 need other markers of kidney damage to diagnose
    • 3 – Moderate reduction in GFR (30-59 mL/min/1.73m)
    • 4 – Severe Reduction in GFR (15-29 mL/min/1.73m)
    • 5 – Kidney Failure (GFR < 15 mL/min/1.73m or dialysis)
    • Usually counted as CKD when GFR < 60 mL/min/1.73 m
      • Or if urinary albumin to creatinine ration >65 mg/mmol

 

Risk factors

  • Diabetes
  • Hypertension
  • Age >65 years
  • Obesity
  • Smoking
  • Heart disease
  • African/SE Asian ethnicity
  • Family history/genetic abnormality
  • High cholesterol

 

Differential diagnoses

  • Acute kidney injury
  • Lupus
  • Renal artery stenosis
  • Kidney cancer

 

Epidemiology

  • Prevalence of 4% in UK adults
  • Kidney disease is the 9th biggest cause of death in the US
  • Increased risk of hospitalisation and death

 

Aetiology

  • Congenital and inherited
    • Polycystic kidney disease
    • Oxalosis – high levels of oxalate, causes frequent kidney stones
  • Glomerular disease
    • Lupus
    • Polyangitis (type of vasculitis)
    • Diabetic nephropathy (glomerulosclerosis)
    • Amyloidosis
    • Systemic sclerosis
    • Accelerated/malignant hypertension
    • Sickle cell disease
  • Vascular disease
    • Hypertensive nephrosclerosis (common in black africans)
    • Vasculitis
    • Renovascular disease
  • Tubulointerstitial disease
    • Tubulointerstitial nephritis – due to drugs, immunological, idiopathic
    • Reflux nephropathy (urine backflow from bladder)
    • TB
    • Schistosomiasis
    • Nephrocalcinosis – calcification, often due to hyperparathyroidism
    • Renal papillary necrosis – diabetes, sickle cell
  • Urinary tract obstruction
    • Kidney stones (calculus)
    • Prostatic disease
    • Pelvic tumours
    • Schistosomiasis
    • Retroperitoneal fibrosis

 

Clinical features

  • Usually asymptomatic/undetected until 50% drop in GFR
  • Fatigue
  • Anorexia
  • Insomnia
  • Itching (pruritis)
  • Nausea
  • Restless leg syndrome
  • Oedema (pulmonary, peripheral sacral)

 

Pathophysiology

  • Metabolic acidosis
    • Inability to excrete H+, and to retain/produce HCO3-
  • Fluid retention
    • Inability to excrete water
  • Uraemia
    • Inability to excrete urea
    • Peripheral neuropathy
    • Restless leg syndrome
    • Gastro-intestinal symptoms (anorexia, nausea, vomiting, diarrhoea)
    • Dry skin
    • Fatigue
    • Encephalopathy
    • Pericarditis
  • Renal osteodystrophy
    • Inability to maintain (reabsorb) appropriate calcium and phosphate
    • Inability to convert 25-Vitamin D to 1,25-Vitamin D
    • Calcium reabsorption from bones

 

Investigations

  • eGFR
    • Estimates glomerular filtration rate based on age, sex, creatine levels, weight (Cockcroft-Gault equation)
    • eGFR of below 60 indicated chronic kidney disease
  • Urea:creatinine ratio
    • Creatinine measured in μmol/L, urea measured in mmol/L
    • Ratio of >100:1 (U:C) is indicative of pre-renal cause
    • Ratio of <40:1 is indicative of intra-renal cause
    • Ratio between 40:1 and 100:1 is normal (post-renal cause will also fall in this range)
    • The ratio is not diagnostic
  • Creatinine clearance
    • Volume of blood cleared of creatinine per unit time
    • Useful analogue of GFR
    • Usually overestimates GFR slightly
  • Inulin clearance
    • Better analogue of GFR than creatinine clearance
    • Requires infusion of inulin, and concentration in blood or urine can be used to calculate clearance rate
  • Urinalysis
    • Protein and/or blood in the urine is indicative of kidney injury
    • Glucosuria with normal blood glucose
  • Urine microscopy
    • White cells – infection
    • Red cells – kidney injury or urinary tract injury
    • Red cell casts – suggests glomerulonephritis
    • Sterile pyuria – papillary necrosis or renal tuberculosis
  • Radiology
    • Ultrasound – check for structural abnormalities, eg cysts
    • CT scan – retroperitoneal fibrosis

 

Management

  • Stop nephrotoxic drugs
  • Maintain appropriate fluid balance
    • Diuretics, fluid restriction etc
  • Treat hypertension, infection etc
  • Dialysis
    • Haemodialysis
      • Essentially a ‘fake kidney’
      • Semi-permeable membrane
      • Dialysate with molecules to match the patients requirement
      • Pumped in opposite directions to maximise diffusion/osmosis gradients
      • Usually have a fistula made in forearm or upper arm for good access
      • Only about 6% filtering capacity of normal kidneys, if have outpatient dialysis
    • Haemofiltration
      • Doesn't use dialysate or countercurrent multiplication
      • Semipermeable membrane allows waste products to diffuse out
    • Peritoneal dialysis
      • Dialysate pumped into peritoneal cavity, and peritoneal membrane used as semi-permeable membrane
      • Most common type is CAPD – continuous ambulatory peritoneal dialysis
        • 2 litre changes 4 times a day
      • APD – automated peritoneal dialysis – fluid exchange is automated by a machine and takes place overnight
      • About 7% normal kidney filtering capacity
  • Kidney transplant

 

Prognosis

  • 28x chance of death if on renal replacement therapy
Chronic kidney disease.docx
Microsoft Word document [16.8 KB]

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