Synopsis
Use symptoms, risk factors, medicines and focused examination to distinguish acute from chronic kidney disease, detect obstruction or systemic nephritis and identify immediate physiological danger.
- Start with time course and baseline: hours to days suggests acute kidney injury, whereas abnormalities persisting for at least three months support chronic kidney disease; an acute-on-chronic picture is common.
- Quantify urine change rather than accepting 'passing less': ask usual and current volume, frequency, nocturia, stream, hesitancy, incomplete emptying, retention, catheter output and recent fluid losses.
- Visible blood, froth, smoky urine, dysuria, flank pain, colic and fever localise different pathways. Painless visible haematuria still needs cancer-pathway assessment even when anticoagulated.
Key red flags
Thirst, vomiting, diarrhoea, bleeding, poor intake or high-output stoma with weight loss, postural symptoms, cool peripheries and low JVP supports reduced effective perfusion, but beta-blockers and older age can blunt tachycardia.
Investigation priorities
Establish direction, acuity and life-threatening biochemical complications.
Management branches
Oliguria, rapid creatinine rise, hypotension, respiratory distress, confusion or suspected severe electrolyte disturbance.
- Perform ABCDE, check observations, ECG and bedside glucose, obtain urgent U&E and venous blood gas, and measure actual urine output with a catheter only when indicated.
- Assess depletion versus congestion, stop or hold clearly unsafe medicines after indication review, and treat sepsis, hyperkalaemia, pulmonary oedema or shock through the appropriate protocol.