Urinary Retention

A common problem which affects 1 in 10 men between 70-79yrs and 1 in 3 men 80-89yrs (10M:F)

Signs/Symptoms

Unable to pass urine (may be passing small amounts overflow)
Desire to pass urine (reduced in neurological causes e.g. cauda equine)
Suprapubic & loin pain (may not be present in chronic or neurological causes)
Palpable bladder on examination

Causes – Remember to look for causes to treat

Obstructive (prostatic, pelvic mass/cancers, clots, stones, foreign body)
Infectious (balanitis, UTI, herpes/zoster, prostatitis, vaginitis)
Trauma (penile, pelvic, postpartum)
Neurological (spinal disease; injury, caudal equine spina bifida)
Constipation
Medication (opioids, anticholinergics e.g. TCA’s, oxybutynin)

Investigations

Bladder scan (remember to code)
Bloods – FBC & U&E
- Depending on cause: PSA, LFT, Bone profile, culture
Urine dip +/- culture
Appropriate imaging esp. in trauma and neurological causes

Treatment

Catheterisation is the treatment of retention and is also the most effective pain relief in this condition. it is important to document residual volume, if >800ml monitor hourly urine output

(if >800ml on scan its worth using an hourly bag due to risk of Post-Obstructive Diuresis)

Urinary Catheterisation in ED guide – HERE

Post-Obstructive Diuresis (POD) – it can kill

POD is a polyuric state after draining the residual urine
Patients loose >200ml/hr OR >3l/day of urine depleting them of water and salt
Frequency ranges from 0.5-52% but is likely around 1.5%
Mechanism is not clear; medullary dilution, ADH insensitivity, reduced GFR

POD – Risk factors

Large residual volume: often quoted as 1500ml in the literature, but cases published with volumes above 800ml (no good studies found on this)
Single Kidney
AKI (reduced eGFR, elevated Creatanine or Urea)
Oedema/fluid overload
>200ml/hr urine: this is part of the definition of POD, will mean time of onset is 3hours but can be upto 27hours

POD- Actions

Urinary retention patients with any of these risk factors, should be referred to urology. As they may benefit from an extended period of observation, as if POD develops they need close fluid management.

If discharged by urology ensure the patient knows if they are filling the (500ml) leg bag within 3hrs to return.

Disposal

At risk of POD: refer to urology
Causes requiring admission: ensure appropriate admission and investigation
No requirement for admission:
- Treat any treatable causes
- Arrange appropriate follow-up
- District nurse to TWOC at 1 week – leave message with “Single point of Access”

Refferences

A. Hamdi, Severe post-renal acute kidney injury, post-obstructive diuresis and renal recovery. BJUI 2012; Vol 110: E1027 – E1034
C. Halbgewachs, Postobstructive diuresis; Pay close attention to urinary retention, Canadian Family Physician, 2015; Vol 61: 137-42
K. Limjunyawong. Prevalence and risk factors of post obstructive diuresis afterpercutaneous nephrostomy in obstructive nephropathy patients. The Thai Journal of Urology 2017: Vol 38: 9-19
https://www.resus.com.au/2018/01/30/postobstructive-diuresis/