Anuria & Oliguria
at the bedside
- airway, breathing, circulation; full vitals, IV access; cardiac monitor if K⁺ is high or unknown
- how much urine, over what period, how measured → last documented output, hourly trend, 24 h balance; the chart, not the impression; hourly from now
- catheter in → kinks, bag position, bypassing or leakage, distended bladder; blocked → flush or replace by catheter type and local protocol, then recount
- no catheter → last void, palpable bladder, bladder scan when retention is suspected; catheter only for confirmed retention or when hourly measurement is clinically necessary, not just to measure → urinary retention
- dry, overloaded or obstructed → JVP, mucosa, edema, crackles, bladder; latest creatinine and K⁺ against the baseline; the answer decides the treat block
- definition → oliguria < 0.5 mL/kg/h for ≥ 6 h; anuria < 100 mL/day; sudden anuria is acted on now, not after 6 h
- K⁺ now → on a gas or i-STAT; 12-lead ECG if K⁺ ≥ 6.0 mmol/L, unwell, or any arrhythmia concern
escalate now if
- K⁺ ≥ 6.0 mmol/L or any ECG change → urgent assessment and ECG, treat by level and ECG → potassium
- hypoxemia, respiratory distress or instability with crackles or edema → pulmonary edema → fluid overload; crackles or edema alone are not the emergency
- severe or worsening acidosis (pH < 7.1 as a marker), drowsy, or pericardial rub → dialysis criteria, nephrology and ICU now
- hypotension or shock → hypotension
- distended bladder → decompress now; failed catheterization, fever with obstruction, bilateral obstruction or an obstructed single kidney → obstruction, urology now
- still oliguric after the fluid challenge → not a diagnosis: reassess perfusion, volume and obstruction before any more fluid → reassess
differentials
- pre-renal → hypovolemia, sepsis, heart failure, cirrhosis; losses, poor intake or poor perfusion in context, bland urine; oliguria can occur in heart failure or cirrhosis despite peripheral edema
- renal (intrinsic) → ATN after hypotension, sepsis or nephrotoxins; interstitial nephritis (new drug, rash, eosinophils); glomerulonephritis (blood and protein, casts); rhabdomyolysis (CK, dark urine)
- post-renal → prostate, stones, pelvic malignancy, blocked catheter; distended bladder, hydronephrosis, anuria that is complete
- not oliguria → output not charted, catheter bypassing, bag not emptied
focused check
- fluid balance → intake vs losses (vomiting, diarrhea, bleeding, drains), last 24 h chart, weight trend
- recent events → hypotension, sepsis, surgery, contrast, rhabdomyolysis risk (immobility, statin, seizure)
- drug chart → NSAIDs, ACEi / ARB, diuretics, aminoglycosides, vancomycin, contrast, new drugs this week; diuretic given today and the response to it
- history → CKD and baseline creatinine, single kidney, prostate, stones, pelvic malignancy
- exam → dry (mucosa, low JVP, tachycardia) vs overloaded (edema, raised JVP, crackles); palpable bladder; rash; catheter and tubing
send now
- RFT and K⁺ → compare with the most recent result, stage against the baseline → acute kidney injury
- VBG → if acidosis, shock or hyperkalemia is suspected → venous blood gas
- Ca, Mg, PO₄, CBC → moderate to severe AKI or no clear cause; CK → only if rhabdomyolysis is suspected
- ECG → hyperkalemia or clinical concern
- urinalysis and microscopy → when AKI is suspected: blood and protein (glomerulonephritis), muddy brown casts (ATN), white cells (interstitial nephritis, infection); culture if infection is possible
- bladder scan → when retention is suspected, before any catheter
- renal ultrasound → if obstruction is suspected or the AKI is unexplained, within 24 h; tonight if an infected obstructed kidney or a single kidney is possible; CT KUB if stones are suspected
- FENa → an adjunct only: unreliable after diuretics, in CKD and in sepsis; it never decides the fluids
calculator FENa · MDCalc ↗︎
treat
pre-renal
- hypovolemic → balanced crystalloid 250–500 mL IV if appropriate; reassess BP, perfusion, breathing and urine output before every further bolus; stop when euvolemic or congestion appears; maintenance fluids are not automatic
- sepsis → fever; heart failure → dyspnea
- cirrhosis → volume status and reversible causes first (bleeding, infection, diuretics, lactulose losses); suspected HRS-AKI, or a question of albumin → hepatology → liver function
- no urine response to fluids → does not prove intrinsic AKI: reassess perfusion, hemodynamics, obstruction and the trend → reassess; more fluid only if still hypovolemic
renal (intrinsic)
- review the drug chart → hold or adjust NSAIDs, ACEi / ARB, diuretics, aminoglycosides and contrast as the picture demands, not indiscriminately; hold metformin and SGLT2 inhibitors; vancomycin by level → vancomycin
- dose the rest by the trajectory → eGFR lags a changing creatinine: dose antibiotics, LMWH, opioids (morphine accumulates, prefer fentanyl), gabapentinoids and digoxin by the AKI trend, urine output, drug levels and pharmacy
- rhabdomyolysis → isotonic fluids if appropriate, individualized; CK, K⁺, calcium, creatinine and urine output; do not escalate fluids in persistent anuria or overload; severe → nephrology
- glomerulonephritis or interstitial nephritis suspected → nephrology today; steroids are their decision
- contrast needed → risk-based: IV balanced crystalloid when AKI is present, unless overloaded or in heart failure; no NAC; do not delay urgent imaging
- staging, nephrotoxin list and full detail → acute kidney injury
post-renal (obstruction)
- suspected retention → bladder scan, then decompress; existing catheter → tubing and patency; irrigate or replace if obstructed, by catheter type and local protocol
- not relieved, or hydronephrosis → upper-tract obstruction → urology (nephrostomy or stent); bilateral or single kidney → tonight
- fever with obstruction → infected obstructed kidney: antibiotics and decompression within hours → empiric antibiotics
- post-obstructive diuresis → urine > 200 mL/h for 2 consecutive hours, or > 3 L/24 h: strict input and output, electrolytes every 6 h, replace cautiously by volume status, not 1:1 → urinary retention
fluid overload
- sit upright; oxygenation and work of breathing; oxygen only if SpO₂ < 90%
- loop diuretic by prior exposure → furosemide 40 mg IV if diuretic-naive, or double the daily oral dose given IV; adjust for renal function, BP and degree of congestion, then judge the response → dyspnea
- restrict fluids by congestion and total intake, not a fixed figure; diuretics treat the overload, not the AKI; never when dry
- refractory pulmonary edema, or desaturating → nephrology and ICU now
dialysis (RRT): nephrology and ICU now
- K⁺ refractory to medical treatment
- severe or refractory acidosis: pH < 7.1 is a marker, judged with the cause, trend and response, not a threshold on its own
- overload not responding to diuretics
- uremic encephalopathy or pericarditis
- dialyzable poison (lithium, methanol, ethylene glycol, salicylate, metformin lactic acidosis)
- no creatinine or urea number on its own mandates dialysis
reassess
- when → after every fluid bolus or diuretic dose, then with each hourly output
- what → urine output trend, BP, perfusion, fluid balance, breathing and SpO₂, bladder; response to what was given
- bloods → repeat creatinine, K⁺ and gas by severity and after any correction, at least daily; daily weight
- not improving → back to dry, overloaded or obstructed; persistent oliguria is a prompt to re-examine, not a diagnosis; nephrology today if the cause is unclear or the stage rises
- hand over → working cause, urine output trend, catheter status, fluids and diuretics given, drugs held or adjusted, pending investigations, dialysis triggers, who to call
evidence
| source | type |
|---|---|
| KDIGO AKI guideline (definition, staging, RRT indications) | international guideline |
| NICE NG148 · Acute kidney injury: prevention, detection and management ↗︎ | national guideline |
| AAST Critical Care Committee 2022 · Trauma Surg Acute Care Open · rhabdomyolysis clinical consensus ↗︎ | specialty-society consensus |
| ACR / NKF 2020 · Kidney Med · intravenous iodinated contrast in kidney disease, consensus statements ↗︎ | specialty-society consensus |
| ACR Manual on Contrast Media, 2024 edition | specialty-society guidance |
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 Oct 2026file complaint/anuria-oliguria