Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

  • Neurological: MS, Syphilis, Spinal Cord Compression
  • Pedunculated Bladder Tumour
  • Traumatic Rupture of Urethra
  • Foreign Body Inserted into Anterior Urethra
  • Phimosis
  • Psychological

Ready Reckoner

Key distinguishing features of the most common diagnoses

Prostatic HypertrophyDrugsConstipationBladder NeckUTI
Enlarged Prostate PRYesNoNoNoPossible
Young PatientNoPossibleNoPossiblePossible
Abnormal UrinalysisPossibleNoNoNoYes
Palpable ColonNoNoYesNoNo

Possible Investigations

Likely:Urinalysis, MSU.

Possible:U&E, PSA, ultrasound, cystoscopy

Small Print:Neurological investigations, prostatic biopsy, urethrography (all hospital-based investigations).

  • Urinalysis of any urine available may confirm a UTI as the cause; may also reveal microscopic haematuria if a stone or bladder tumour.
  • MSU: Will confirm infective agent in UTI.
  • U&E: Renal failure may follow chronic retention
  • PSA may be worth considering if preceding symptoms of prostatism or abnormal prostate on examination.
  • Specialist tests may include: Renal ultrasound (reveals obstruction and pelvic masses), cystoscopy (may be diagnostic and therapeutic for stones, stricture, bladder outflow obstruction and bladder tumour), neurological investigations (e.g. spinal cord imaging if cord lesion suspected), prostatic biopsy (if suspicious area of prostate palpable) and urethrography (for stricture).

Top Tips

  • Do not overlook faecal impaction in the elderly patient as a cause of urinary retention.
  • ‘First-aid’ relief of retention when the cause is a painful perineal condition (e.g. balanoposthitis, herpes simplex or UTI) may be achieved by encouraging the patient to urinate while immersed in a warm bath.
  • Anuria can be mistaken for retention. A straightforward clinical assessment should differentiate the two conditions.

Red Flags

  • A history suggesting a disc prolapse with urinary retention indicates possible cord compression – admit immediately.
  • Sudden stoppage of urine with a pain like a blow to the bladder and passage of a few drops of blood is pathognomic of urethral calculus.
  • Beware of any drugs with anticholinergic side effects in patients with a history of outflow obstruction – they may precipitate acute retention.
  • Avoid catheterisation when sepsis is likely (e.g. possible UTI) – instrumentation may result in septicaemia. Instead, admit to hospital for catheterisation under appropriate antibiotic cover.
  • Do not catheterise the patient with chronic retention; admit for controlled drainage. Sudden decompression can result in haematuria and renal complications.

Published: 2nd August 2022 Updated: 10th April 2024

Report errors, or incorrect content by clicking here.