Anuria & Oliguria
ABCs
- check vitals → hypotension, tachycardia, hypoxia
- cardiac monitor if unstable
- secure IV access
- document urine output
- oliguria < 0.5 mL/kg/hr for ≥ 6 hr
- anuria < 100 mL/day
- confirm true oliguria
- catheter in situ → flush, check for kinks or blockage
- no catheter → ask about voiding; bladder scan for retention
treat urgently
- hyperkalemia with ECG changes → see potassium
- severe metabolic acidosis
- pulmonary edema or fluid overload (raised JVP, crackles, desaturation)
don’t miss obstruction
- no catheter → bladder scan; catheterize if significant residual
- catheterized, still anuric → flush or replace; no improvement → suspect upper-tract obstruction
- hydronephrosis on imaging → Urology
- fever + obstruction → urological emergency: urgent decompression + antibiotics
escalate further if
- persistent oliguria despite adequate resuscitation → Nephrology
- refractory hyperkalemia, severe acidosis, or fluid overload → ICU / urgent dialysis
- persistent hemodynamic instability → shock management
- fluid overload causing respiratory failure → respiratory support
- deterioration or unclear cause → escalate early
HPI & examination
- history
- fluid balance: intake vs losses (vomiting, diarrhea, bleeding)
- recent events: sepsis, surgery, hypotension, trauma
- known CKD / ESRD
- nephrotoxins: NSAIDs, ACEi / ARB, aminoglycosides, vancomycin, contrast
- diuretics (overuse → pre-renal)
- urological history: BPH, stones, pelvic malignancy
- examination
- depletion: dry mucosa, low JVP, tachycardia
- overload: edema, raised JVP, crackles
- bladder: palpation / percussion for distension; bladder scan
- catheter: check for kinking or blockage
workup
| test | why |
|---|---|
| CBC, U&E, creatinine | confirm AKI, compare to baseline |
| calcium, magnesium, phosphate | deranged in AKI; phosphate rises, calcium falls |
| VBG ± lactate | acidosis, perfusion |
| CK | rhabdomyolysis (crush injury, prolonged immobility, statins) |
| ECG | hyperkalemia changes |
| urinalysis ± microscopy | blood, protein, casts (muddy brown = ATN, red cell = GN); culture if infection suspected |
| bladder scan | first-line if retention suspected; before catheterization |
| renal ultrasound | hydronephrosis / obstruction; CT KUB if stones suspected |
causes
| type | clues | do |
|---|---|---|
| pre-renal | hypovolemia, sepsis, HF, hepatorenal; dry, tachycardic, ↑ urea:Cr | IV fluids if depleted, treat cause |
| intrinsic | ATN, AIN, GN, rhabdomyolysis; casts, proteinuria, ↑ CK, ↑ Cr | stop nephrotoxins, ± steroids, Nephrology |
| post-renal | BPH, stones, malignancy; distended bladder, hydronephrosis | catheterize, imaging, Urology |
management
- fluids: if hypovolemia plausible, give 250–500 mL crystalloid (NS or balanced), reassess before repeating; do not give into overload
- stop / hold nephrotoxins: NSAIDs, ACEi / ARB, aminoglycosides, vancomycin; hold metformin (lactic acidosis risk), SGLT2i; renally adjust all other meds
- hyperkalemia / acidosis → ECG changes: calcium gluconate immediately, then shift K+ (insulin–glucose, nebulized salbutamol); full protocol
- fluid overload → IV furosemide; diuretics do not treat AKI or improve renal recovery
- dialysis / RRT → Nephrology / ICU for: refractory hyperK, severe acidosis unresponsive to therapy, refractory overload, uremic complications (encephalopathy, pericarditis), select toxins; no creatinine threshold alone mandates dialysis
- post-obstructive diuresis → monitor closely; replace a proportion of losses guided by volume status + electrolytes, not 1:1 (perpetuates diuresis)
Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.
free the on-call checklist covers the whole shift on one printable page.
studying for the IM exam? the IM Rapid Review covers AKI and oliguria. see the sample chapter.
reviewed Jul 2026updated Aug 2026file complaint/anuria-oliguria