Acute and Chronic Urinary Retention (1*)

Question 1

What is the pathophysiology of Chronic retention?
→ How does this make it different from Acute retention?

How else do Chronic retainers differ from Acute retainers?

What are the ways in which Chronic retention is classified?
→ Which type is worse and why?

What are its complications?

Answer 1

➊ Incomplete bladder emptying over a long period of time. Over time, the bladder tends to grow larger and larger and may eventually fail to contract at all.
→ Means they tend to hold a lot more urine than those in acute retention

➋ They don’t have any pain or urgency

➌ Low or high pressure by the presence of detrusor activity
→ High pressure (Detrusor activity increases the pressure), which increases the risk of upper renal tract damage

➍ • UTI
• Kidney stones
• Hydronephrosis
• AKI

Question 2

What are the obstructive causes?

What are the neurological causes?

What are the infectious causes?

What are the iatrogenic causes?

Answer 2

➊ • Most common is BPH
• Constipation
• Urethral strictures
• Prostate cancer

➋ • Cauda Equina Syndrome
• Spinal cord injury
• MS

➌ • UTIs - Can cause weakness of the bladder or swelling of the urethra esp. in those with already narrowed outflow tracts
• Prostatitis

➍ • Anticholinergics e.g. Oxybutynin – Block parasympathetic activity on detrusor and their inhibitory effects on the sphincters
• A1 agonists e.g. Phenylephrine

N.B. Post-operative retention is common in older pts who were under GA

Question 3

How does it present if acute?

How does it present if chronic?

What will be felt O/E?

Answer 3

➊ • Acute suprapubic pain and tenderness
• Inability to micturate

➋ Most only have LUTS, and only have a palpable bladder if it becomes large

➌ Palpable distended bladder, Enlarged prostate if it’s the cause

Question 4

Which investigations need to be done?

Answer 4

• Bloods – FBC, CRP, U&Es
• Urinalysis
• Bladder US
• Post-void bladder scan – Shows volume of retained urine
• DRE – check for BPH

Question 5

Management:
What is the most important thing to do?

What else should be done once managed?

What do those with a large retention need to be monitored for post-catherisation?
→ What happens here?
→ Urine osmolarity needs to be taken to determine how to manage it. How does the management differ with the result?

Answer 5

➊ Immediate catheterisation – Measure the volume drained post-catheterisation

➋ Treat the underlying cause

➌ Post-obstructive Diuresis (> 200ml/hr for 2 consecutive hrs)
→ Kidneys can over-diurese due to the loss of their medullary concentration gradient, which can take time to re-equilibrate
→ • Iso-osmolarity – Indicates the kidneys don’t need to concentrate the urine and is consistent with physiological diuresis and is generally self-limiting
• Hyper-osmolarity – Indicates the kidneys are concentrating the urine so post-obstructive diuresis has/is resolving
• Hypo-osmolarity – Indicates salt-wasting and the inability for the kidneys to concentrate urine. This is pathological and pts needs replacement IVF.