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
red flags
treat urgently
- hyperkalemia or acidosis → Calcium gluconate, insulin + glucose, ± sodium bicarbonate; dialysis if refractory
- ECG changes of hyperkalemia
- fluid overload (raised JVP, crackles, edema)
don’t miss obstruction
- anuria despite a Foley in situ → suspect obstruction
- distended bladder or hydronephrosis → Urology
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, contrast
- diuretics (overuse → pre-renal)
- examination
- volume status, dehydration: dry mucosa, low JVP, tachycardia
- volume status, overload: edema, raised JVP, crackles
- bladder: palpation / percussion for distension
- Foley: check for kinking or blockage; bladder scan if unclear
workup
| test | why |
|---|---|
| Urea, Creatinine, electrolytes | confirm AKI, assess severity |
| urinalysis ± culture | casts, protein, infection |
| VBG ± lactate | acidosis, perfusion |
| ECG | hyperkalemia changes |
| ultrasound or CT KUB | rule out obstruction |
causes
| type | clues | do |
|---|---|---|
| Pre-renal | hypovolemia, sepsis, HF, hepatorenal; dry, tachycardic, ↑ urea:Cr | IV fluids + treat the cause |
| Intrinsic | ATN, AIN, GN; casts, proteinuria, ↑ Cr | stop nephrotoxins, ± steroids, Nephrology |
| Post-renal | BPH, stones, malignancy; distended bladder, hydronephrosis | Foley, imaging, Urology |
management
- hypovolemia → IV fluids (NS or balanced)
- hyperkalemia / acidosis → treat urgently: Calcium gluconate, insulin + glucose, ± sodium bicarbonate; dialysis if refractory
- post-obstructive diuresis → monitor closely, replace ~1:1 fluids
escalation
- persistent oliguria despite adequate fluids → Nephrology
- anuria despite a Foley in situ → suspect obstruction → Urology
- severe electrolyte disturbance or acidosis → ICU / urgent dialysis
- deterioration or unclear cause → escalate early and reassess
studying for the IM exam? the IM Rapid Review covers AKI and oliguria in the same format. see the sample chapter.
Last reviewed · May 2026