Acute Tubular Necrosis (ischemia, drugs, or toxins)
Obstruction due to
Calculi, Tumor, Obstructed Foley Catheter
Often a patient will have a diminished urine output after a major operation. This may be the result of fluid and blood loss and d/t response of the adrenal cortex to stress - there is an increase in aldosterone release (adrenal cortex) and ADH release (posterior pituitary) in the first 24 hours after surgery. This results in both salt and water retention.
The oliguria should be temporary and not last more than 24h. If there is a urine output of less than 400ml in the first 24 hours then this warrants investigation.
Review patient immediately
Assess need for urgent resuscitation
1) Does the patient have any symptoms or predisposing conditions that suggest hypovolemia?
Diarrhoea, vomiting, GI bleeding, high fever, low intake (whether oral or IV)
Positional dizziness suggests hypo-volaemia
If post-op: bleeding, wound drainage, infection leading to septicemia
2) Previous symptoms to suggest bladder outlet obstruction from prostatic hypertrophy?
Hesitancy, difficulty voiding, dribbling
i.e. post renal obstruction
3) History of hematuria?
Renal stones can lead to obstruction
4) Is the patient likely to be suffering from acute renal failure?
Nephrotoxic drugs (aminoglycoside AB’s and NSAIDs)
Exposure to nephrotoxic agents (contrast, chemotherapy)
5) Any underlying diseases/procedures that could result in oliguria?
Cardiac failure, cirrhosis, epidural infusion
6) Symptoms suggestive of uremia?
Nausea, vomiting, anorexia, insomnia, mental status changes
Vital signs - ABCs
decrease in weight suggests volume depletion
Hypertension (volume overload or if long standing can cause renal insufficiency)
Check orthostatic BP
Irregularly irregular pulse suggests atrial fibrillation (a common cause of emboli)
Review meds and stop all nephrotoxic drugs (Aminoglycosides, NSAIDS, COX-2 inhibitors)
Adjust doses of renally excreted drugs
Address all the Septic Foci (ABx, surgical drainage, UTI)
Mx of Oliguria….
Volume challenge (i.e. 500mL NS for 30 mins)
Monitor volume replacement to ensure circulatory adequacy (i.e. use arterial and R. heart catheters to measure CVP to be above 10mmHg)
Follow hourly urine output (w a catheter in place)
Consider additional measures (some doctors may disagree with this)
Frusemide (but usually reserved for fluid overload)
Consider frusemide and mannitol
Emergency dialysis in the following:
Severe hypovolemia unresponsive to diuretics
Pericarditis secondary to uremia
Severe uremic symptoms or encephalopathy
Post Renal causes
Place a catheter, if immediate flow starts then urethral obstruction is very likely
If catheter already present, replace or irrigate it as it could be obstructed
Consult a urologist
Oliguria/ARF Systemic Complications
Infections of urinary tract & lungs due to uremia
Up to 70% of pts. with ARF.
#1 cause of ARF morbidity/mortality
Kidney makes EPO, ↓ EPO anemia (HCT 20-30)
“ 3 rd space disease”
Salt and Water retention (esp. in pre-renal failure)
Pulmonary edema, Pleural effusion, & ascites
↓ excretion of phosphate impaired GI absorption of Calcium.
↓ glomerular filtration, ↓ tubular secretion
Malaise, nausea, and muscle weakness.
A cardiac emergency
Metabolic Acidosis w/ ↑ anion gap
↓ excretion of acids & ↓ tubular reabsorption of bicarbonateresults in metabolic acidosis with a high anion gap.
Hypotension, Kussmaul’s respirations
Oliguria in an alert patient that is associated with normal pre-existing renal function and cardiovascular stability, is unlikely to require intervention unless it persists for four hours or more. So, wait and see…
If oliguria is associated with other symptoms or signs suggestive of fluid depletion, it should be treated initially with a fluid challenge.
In all cases of oliguria it is important to exclude obstruction of the urinary tract or urinary catheter.
Diuretics should not be used to treat oliguria and should be reserved for fluid overload.
Dopamine should not be used to treat oliguria or to prevent renal failure.