>EM Reflections October 2020 – Acute Urinary Retention

Big thanks to Dr. Joanna Middleton for leading the discussions in October

All cases are imaginary, but highlight learning points that have been identified as potential issues during rounds.

Edited by Dr. Mandy Peach


 

Acute Urinary Retention (AUR)

  • Categorized as obstructive, infectious/inflammatory, neurological, medication related
  • Physical exam should include a DRE and neurological exam
  • Investigations should include a U/A +/- C&S, creatinine, electrolytes +/- CBC
  • Consider a renal US if any renal impairment
  • PSA – defer at least 2 weeks, as acute urinary retention can cause elevation
  • Consider risk factors for post-obstructive diuresis

Case

A 60 yo male presents to the emergency department with inability to void over 8 hours, despite feeling urgency. He complains of increasing lower abdominal discomfort. He denies any infectious symptoms or new medications. He denies any back pain or recent injury. He does have a history of hesitancy and poor urine stream. He has never had a prostate exam and has no family doctor. His vital signs are within normal limits. He has a significantly distended bladder on physical exam.


Indications to insert a catheter1:

  • Inability to pass urine > 10 hours
  • Abdominal discomfort with bladder distention
  • Signs of acute kidney injury secondary to obstruction
  • Infectious cause of retention
  • Overflow incontinence

You decide to insert a urinary catheter. What else should you consider as part of your physical exam?

Consider the 4 main causes of urinary retention:

In this male patient it is pertinent to do a prostate exam to check for enlargement as well as a thorough neurological exam.

On exam you palpate a large, firm prostate. You are suspicious of prostate cancer – do you do a prostate specific antigen (PSA)?

No – acute urinary retention can transiently elevate PSA measurements up to 2 fold, this can persist for up to 2 weeks2. Defer PSA testing until after this time.

The U/A is negative for infection. The electrolytes are normal but the patient has an acute AKI with an elevated creatinine. Does this patient require renal imaging?

Consider renal imaging in any patient with AUR and abnormal renal function to assess for anatomical cause.

2 hours has passed and you reassess the patient – 1L of urine has drained upon insertion. A minimal amount has been draining since. The post-void residual is now 20 cc.

Is this patient at risk of post-obstructive diuresis?

Risk factors:

  • Abnormal electrolytes or acute creatinine elevation
  • Volume overload
  • Uremic
  • Acutely confused

Although the patient does have an abnormal creatinine, clinically he does not show signs of post-obstructive diuresis which is defined as urinary output > 200 mL for at least 2 hours after urethral catheter insertion, or > 3L in 24hrs AFTER the initial emptying of the bladder. Patients with any risk factors for post-obstructive diuresis should be observed in the ED for 4 hours.

After an appropriate observation period you discharge the patient with an urgent referral to urology given the acute presentation and abnormal prostate exam. You are sending the patient home with an indwelling catheter.

What is the optimum duration of catheter insertion? Does this patient require antibiotics?

Trials are contradictory. Some found increased likelihood of spontaneous voiding after 7 days, while an observational study found improved success if insertion was less than 3 days3.

Expert opinion from urology suggests duration of 7 days to avoid risk of re-catheterization1.

Routine antibiotics are not recommended unless the cause is thought to be infectious. However, if prostatic enlargement is thought to be the cause an alpha-blocker like tamsulosin can be beneficial1

 


 

References for further reading:

1 Ep 143 Priapism and Urinary Retention: Nuances in Management. Emergency Medicine Cases. https://emergencymedicinecases.com/priapism-urinary-retention/

2 Aliasgari, Soleimani, Moghaddam (2005).The effect of acute urinary retention on serum prostate-specific antigen level. Urology journal. Spring 2005;2(2):89-92

3 Acute Urinary Retention. Uptodate. https://www.uptodate.com/contents/acute-urinary-retention?search=post%20obstructive%20diuresis&source=search_result&selectedTitle=1~5&usage_type=default&display_rank=1#H537553020


 

Authored and Edited by Dr. Mandy Peach

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