see also:

• urology
• acute urinary retention
• acute kidney injury (AKI) / acute renal failure (ARF)
• the shocked hypotensive patient

• inability to pass urine is a common ED presentation, and as with renal failure falls into 3 main categories:
  • acute urinary retention
  • pre-renal causes such as the shocked hypotensive patient
  • renal causes (acute kidney injury (AKI) / acute renal failure (ARF))

• ask patient to void
• if unable to void, assess bladder volume ASAP:
  • clinically
    • bladder is percussible when it contains > 150mL urine and may be palpable when > 200mL
  • bladder scanner
    • may give false positive results, eg. ascites
  • calculate volume using an ED ultrasound machine
    • US probe placed 3cm above PS in the midline
    • image bladder in sagittal and transverse planes, taking measurements of width of transverse image (W), AP depth of transverse image (D1) and superior-inferior length of sagiital image (D2) (all in cm)
    • calculated volume in mL = W x D1 x D2 x 0.52
    • volume percent error rate when performed by nurses ~9% (cf 18% when using a bladder scanner ¹⁾ )
    • allows visual detection of ascites as a differential to a positive bladder scan
• if bladder scan indicates a large volume (eg > 300mL after failing to void)
  • if patient still unable to void, then, if no C/I, insert IDC (usually 14-18F catheter in adults, but if frank haematuria with clots, use a 3-way catheter to allow bladder washouts)
    • record volume drained in 1st 10-15minutes
    • if > 400mL, leave IDC in place and Mx as per acute urinary retention
    • if draining urine but < 200mL, it is not acute retention and IDC should probably be removed unless other indication to keep it in situ
    • if 200-400mL drained, consider removing IDC depending upon clinical scenario
    • if minimal urine from IDC:
      • check with USS to exclude false positive bladder scan scenarios such as ascites
    • if unable to pass an IDC:
      • consider trying with a smaller catheter, eg. 10-12F
      • call a senior doctor to consider trying
    • if C/I to IDC or still unable to pass an IDC
      • call urology reg for advice
      • may need to have an urgent suprapubic catheter inserted, preferably with US guidance
• if empty bladder then consider pre-renal and renal causes:
  • excl. and if present, treat, the shocked hypotensive patient
  • check U&E, etc to assess for acute kidney injury (AKI) / acute renal failure (ARF)