urinary output decreased Flashcards
Questions to ask regarding decrease in urinary output
- what was the reason for admission
- vitals
- how much urine passed in the last 24 hrs
- does the pt have indwelling catheter
- is the pt complaining of abdo pain- associated with acutely distended bladder
what is oliguria?
Defined as <400mL/day OR <20mL/hr and may be the earliest sign of renal impairment
what is complete anuria suggestive of?
- mechanical obstruction of bladder outlet
- a blocked IDC
- obstructed single kidney
- acute renal failure
If there is an IDC present and the pt is anuric what can you ask the nurse to do?
flush the catheter with 20-30mL normal saline to dislodge sediments or clots
What is the significance of a UEC in a pt with low urinary output?
- a serum potassium >5.5mmol/L can indicate hyperkalemia
- elevated serum urea and creatinine levels and their ratio are a guideline to assess the degree of renal insufficiency
What are some pre-renal causes of reduced urine output?
- absolute decrease in circulating blood volume leading to renal hypoperfusion E.g:
- inadequate fluid intake
- increase loss of blood or fluids
- 3rd spacing of fluid (e.g pancreatitis or bowel obstruction) - cardiac pump failure- MI (cardiogenic shock), CCF
- effective decrease in BV (vasodilation)- sepsis, anaphylaxis, neurogenic, vasodilatory drugs, anaesthetic agents
- obstruction to circulation- constrictive pericarditis, cardiac tamponade, PE
- locally reduced renal perfusion
- renal artery or vein occlusion secondary to thrombosis or stenosis
- noradrenaline,adrenaline
- aortic dissection
What are some renal causes of reduced urine output?
- Acute Tubular necrosis (ATN)
- Glomerulonephritis
- Interstitial nephritis
What are some post-renal causes of reduced urine output?
- upper renal tract obstruction (bilateral ureteric obstruction on single ureteric obstruction of a single kidney): can be due to stone, blood clot, sloughed necrotic papilla, retroperitoneal fibrosis, retroperitoneal tumor.
- Lower urinary tract obstruction (bladder outlet obstruction): prostatic hypertrophy, carcinoma of the cervix, stone or clot lower down, urethral stricture
- Blocked indwelling urinary catheter
What is ATN and what can cause it?
Acute tubular necrosis is kidney injury caused by damage to the kidney tubule cells.
- usually secondary to pre-renal causes like intravascular depletion, significant hypotension and renal ischemia
- medications (e.g. aminoglycosides, amphotericin B, IV contrast, chemotherapy)
- poisons (e.g. ethylene glycol, mercury, carbon tetrachloride)
- endogenous substances (e.g. myoglobin, bence-Jones protein, amyloid)
What is glomerulonephritis and what can cause it?
Glomerulonephritis is a group of diseases that injure the part of the kidney that filters blood (called glomeruli).
It can be caused by:
- Diabetes Mellitus
- neoplasia
- medications (e.g. NSAIDs, penicillamine-DMARD)
- connective tissue disease (e.g scleroderma, SLE)
- vasculitis (e.g. polyarteritis nodosa, Wegners granulomatosis)
- Infection (e.g. post strep, malaria, HIV, hepB)
- Autoimmune (e.g. IgA nephropathy=berger disease, Henoch-Schonlen purpura, Goodpasteurs syndrome)
- Genetic (e.g. Alport syndrome with hearing loss)
What is interstitial nephritis and what can cause it?
Interstitial nephritis is a kidney condition characterized by swelling in between the kidney tubules.
Causes include:
- Infection (e.g. pyelonephritis, viral, fungal)
- medications (e.g. NSAIDs, penicillin, cephalosporins, sulfonamides, lithium, cyclosporins)
- malignancy (e.g. lymphoma or leukaemia)
- other (e.g. transplant rejection, reflux, atheroscleroisis, radiation, hypercalcaemia)
What are the major threats to life when you see a patient with reduced urine output?
- hypotension and shock- reduced urine output may be the earliest manifestation of shock
- oliguric acute renal failure is associated with an acute life threat from:
- hyperkalemia (cardiac arrhythmias, paralysis, muscle weakness)
- metabolic acidosis (kussmaul’s breathing, raised anion gap)
- acute hypertension
- pulmonary edema secondary to salt and water retention
What can you do at the bedside of a pt with low urine output?
- quick-look test- does the pt look unwell?, is the pt restless with abdo discomfort (retention)?
- airway and vitals: look for evidence of dehydration causing pre-renal hypoperfusion. Rise in HR>20, SBP>20 or any fall in DBP when standing can suggest signifcant hypovolemia
- resting tachy alone may be related to decrease intravascular volume, pain of distended bladder or infx.
- acute HTN with oedema may result from acute glomerulonephritis
- fever suggests sepsis secondary to a UTI, pyelonephritis or systemic bacteraemia
- Selective history and chart review:
Look for pre-disposing factors in hx
Look at med chart for specific nephrotoxic drugs especially in combo of ACEi + diuretic +NSAID, an aminoglycosides and amphotericin B are both nephrotoxic, IV contrast material with an ACEi, CCF pt taking NSAID
does the onset coincide with the commencement of new drug?
What does the recent urea to creatinine ratio indicate?
- A urea to creatinine ratio> 10 with urine specific gravity of >1.020 or urine sodium concentration of <20mmol/L suggest pre-renal cause
- A urea-creatinine ratio<10 with urine specific gravity <1.020 or urine sodium conc >20mmol/L suggests renal cause like ATN
What investigations would you consider in a pt with low urine output?
- FBC (low Hb suggest chronic kidney problems or acute blood loss), UEC (hyperkalemia?) , BGL, LFT
- autoantibodies (if indicated)
- blood gas (raised anion gap metabolic acidosis from uraemia)
- ECG (peaked T waves, depressed ST segments, prolonged PR interval, loss of P wavves and wide QRS– signs of hyperkalemia)
- bedside bladder scan to measure residual bladder volume
- urine dipstick and MCS including cells and casts
