--- module: 020-01 language: en chapter: 20 title: "Acute Kidney Injury, Chronic Kidney Disease, and Renal Pharmacology" module_title: "Foundations" source_sha256: 5e9513dbb669204a12b6778c3d6c2b5f835b408d6bfc48dd3b5f7178562244bb --- # Acute kidney injury, chronic kidney disease, and renal pharmacology ## Recognising acute kidney injury ### Hours to days, versus months for chronicity ### Rising creatinine, falling urine output, or both #### Creatinine rises only after filtration falls #### Fluid balance dilutes or concentrates it ### Oliguria can occur without structural damage ### Non-oliguric injury can still be severe ### Classify perfusion, intrinsic injury, obstruction, with overlap ### Review baseline, sepsis, surgery, contrast, medicines ## Reduced perfusion and haemodynamic injury ### Haemorrhage, dehydration, vasodilation, low cardiac output ### Autoregulation balances afferent and efferent tone #### Fails beyond range or when drugs block compensation ### Non-steroidal drugs reduce afferent dilation ### Renin-angiotensin blockers reduce efferent constriction ### Modest change may be filtration, progression needs review ### Sepsis: microvascular, inflammatory, metabolic dysfunction ### Venous congestion raises interstitial pressure ## Intrinsic renal disease ### Acute tubular injury from ischaemia, sepsis, toxins #### Cells detach and obstruct tubular lumens #### Granular casts, then a high-output recovery phase ### Acute interstitial nephritis is often drug-related #### Fever, rash, eosinophilia frequently absent ### Glomerulonephritis: haematuria, protein, hypertension, oedema #### Rapidly progressive disease destroys function quickly ### Thrombotic microangiopathy injures endothelium ### Pigment nephropathy from myoglobin or haemoglobin #### Rhabdomyolysis: creatine kinase, potassium, calcium, acidosis ## Obstruction ### Prostate, stones, tumours, clots, strictures ### Unilateral obstruction may preserve creatinine ### Early blockage may lack dilation, chronic dilation persists ### Post-obstructive diuresis loses salt and water #### Monitor and replace a proportion of losses ## Immediate management and dialysis ### Stop nephrotoxins and adjust drug doses ### Restore perfusion, treat infection, relieve obstruction ### Diuretics do not treat a laboratory category ### Replacement for refractory potassium and acidaemia #### Toxins and uraemic complications, not a creatinine value ### Intermittent haemodialysis removes solute rapidly ### Continuous therapy suits unstable patients ## Chronic kidney disease ### Staged by filtration category and albuminuria #### Both predict progression and cardiovascular risk ### Causes: diabetes, hypertension, glomerular, inherited disease ### Chronicity from old results, imaging, anaemia, bone ### Remaining nephrons hyperfilter and hypertrophy #### Intraglomerular stress and proteinuria drive fibrosis ### Slowing: pressure, albuminuria, glucose, blockade, cessation ## Systemic complications ### Sodium retention, potassium and acid accumulation ### Low erythropoietin and iron restriction cause anaemia ### Phosphate, vitamin D, calcium, parathyroid remodelling ### Uraemic toxins affect nerves, platelets, appetite ### Cardiovascular risk from calcification and load ## Renal prescribing ### Dose follows filtration, stability, dialysis, binding ### Reduce amount, extend interval, or both ### Loading dose follows volume of distribution ### Toxicity: haemodynamic, tubular, crystal, interstitial ### Monitor the expected injury, not undirected tests ### Dialysis removes small, unbound, low-volume drugs ## Assessment and investigation ### Ask about urine, swelling, stones, family, medicines ### Examine pressure, volume, bladder, skin, access ### Integrate blood trends, urinalysis, protein quantification ### Ultrasound, immune tests, microbiology, selected biopsy ### Urgency: rapid loss, active sediment, heavy protein ## Access, transplantation, and prevention ### Fistula durable but slow, graft faster but riskier ### Catheter is immediate but risks infection ### Haemodialysis: hypotension, cramps, disequilibrium ### Peritoneal dialysis: peritonitis, hernia, membrane failure #### Cloudy effluent with pain needs urgent sampling ### Transplant needs immunosuppression and surveillance #### Rejection may be a silent creatinine rise ### Conservative care treats symptoms and plans ahead ### Discharge is not proof of renal recovery ### Pregnancy, contrast, surgery, infection are high risk