Sometimes there can be more than one cause at the same time. Always check that any catheter is not blocked or the end is in the urethra.
- Oliguria < 500 ml Urine output (UO) per day
- Oliguria also been defined UO <0.5 ml/kg/h for
≥6 consecutive hours which is 35 mls per hour for a 70 Kg patient
- Anuria < 50 ml UO per day and suggests injury to both kidneys or obstruction of both kidneys
- A recent evaluation from intensive care patients found that nearly 50% experienced an episode of oliguria during their
intensive care unit (ICU) stay
- Average person excretes 600mOsm of
solute per day.
- Maximal urinary concentration ability is
1200 mOsm/L. Hence at least 0.5 L
of urine needed.
- Urine output is a function of glomerular
filtration, tubular secretion and
- Glomerular filtration is directly depending
on renal perfusion.
- Oliguria indicates a reduction in GFR or a
mechanical obstruction to urine flow.
Causes works same as AKI
- Dehydrated and underfilled
- Cardiac or Liver failure
- Nephrotoxic drugs: penicillins, NSAIDs, cephalosporins, Gentamicin
- Post Renal: Onstruction
- Renal pelvis (Unilateral so oliguria): Renal papillary stenosis
- Ureter (Unilateral so oliguria): Compression, Stone obstructiobn, tumour
- Bladder: TCC bladder, Prostate cancer or BPH, Blocked catheter -0 clot retention
- Urethra: Stricture
- High Intraabdominal pressure
- FBC, U&E, Ca, P, LFT, Bone, Glucose
- Raised CRP; Vasculitis, Infection, Inflammatory
- CXR and AXR: Oedema, abdominal pathology
- Plasma Protein electrophoresis
- Urinalysis: Haematuria - infection or tumour or inflammation, Leucocytes, protein, glucose
- Haematuria and proteinuria are prominent.
- Broad brown granular casts are found in ischaemic or toxic ATN
- Red cell casts in acute glomerulonephritis
- High WCC : Infection, acute interstitial nephritis
- Urine Na: Low in prerenal < 10 mmol/L
- Urine Osmolality : high in prerenal >500mOsm/kg
- ANA, dsDNA, C-ANCA/P ANCA, Anti GBM where vasculitis suspected
- USS renal tracts for hydronephrosis or other lesions
- In most cases the cause is simply a blocked catheter or the patient is dry. Unless they have pulmonary oedema a fluid challenge may be considered with a plan for a clinical review and follow up depending on the overall case.
- Urine retention: always catheterise and measure and keep a strict I/O chart. Ensure that drains and all fluids accounted for. Weight is useful. See section on assessing volume status.
- Assess BP and exclude shock and hypotensive states and treat any cause of coexisting shock and volume fill +/- inotropes as needed.
- Assess fluid status and need for filling - may need a central line. Fluid replace as needed looking for a corresponding diuresis
- Exclude obstruction with a USS where needed and this should be done within 24 hrs
- Stop any nephrotoxic agents. Close monitoring and renal referral if worsening AKI or the oliguria/anuria persists and is non-obstructive
- An obstruction in the renal tracts is a Urology referral as the patient may need stenting