M E E RA L A D WA

ACUTE KIDNEY INJURY

WHAT IS ACUTE KIDNEY INJURY?

• A rapid fall in glomerular filtration rate (GFR)• In practice, since measuring GFR is difficult, we

use a rise in serum urea and creatinine within 48 hours to diagnose.• Often associated with oligo-uria, but not always• Occurs 15% of adults in hospital

CAUSES

• Pre-renal (common)--any cause of shock, e.g. sepsis, hypovolemia-any cause of reduced cardiac output e.g. cardiac failure, severe valvular disease-renal artery stenosis, hepato-renal syndrome-drugs, eg ACE inhibitors

The mechanism is reduced renal perfusion, eventually resulting in acute tubular necrosis (ATN). This is potentially reversible.

WHAT IS THIS?

CAUSES

• Intrinsic renal (less common, but v important to recognise)

-Tubular, eg Multiple myeloma, drugs (aminoglycosides, contrast), rhabdomyolysis

-Interstitial nephritis eg penicillins, NSAIDs-Glomerular; -Hemolytic uremic syndrome (HUS),

thrombotic thrombocytopenic purpura (TTP)‘Rapidly progressive GN’ or ‘crescentic GN’e.g. Goodpasture’s , Systemic vasculitides e.g. SLE,

PAN, Wegener’s granulomatosis, microscopic polyangiitis

CAUSES

•Post-renal (common)

-obstruction of the renal outflow tractEg. stones

BPHTrauma or surgeryTumours of bladder and prostateOther pelvis malignancies e.g. ovarian

INVESTIGATIONS

• Urinalysis – for blood and/or protein. Red cell casts in urine = glomerulonephritis• Urine Bence-Jones protein – for myeloma.

• ‘Renal screen’ – ESR, protein electrophoresis, ANA, ANCA, anti-GBM antibodies, C3/C4

• USS of the renal tract – to look for obstructive uropathy

• Renal biopsy

TREATMENT

• Stop nephrotoxic drugs• Assess volume status and optimise e.g. give

fluids if hypovolemic and dehydrated.

• Treat the cause e.g. antibiotics in sepsis, relieve obstruction, immunosuppressants+ plasma exchange for RPGN

• Renal replacement therapy e.g. hemodialysis

INDICATIONS FOR HEMODIALYSIS IN AKI

• Hyperkalemia, not responding to medical management• Pulmonary oedema, not responding to medical

management• Severe acidosis, not responding to medical

management• Uremic pericarditis or uremic encephalitis

CONCLUSIONS

• Acute kidney injury is common in hospitalised patients

• Patients with AKI with no clear cause should have US of the kidneys within 24 hours

• If a glomerulonephritis is suspected, contact renal specialist team as early as possible