Urology
Question 175 of 180
A 59 year old man presents to the Emergency Department complaining of suprapubic pain. He last passed urine 12 hours ago. Which of the following investigations is most useful in this patient?
Answer:
- Bladder scanning is increasingly available not only in the emergency department, but also on medical wards. These scanners allow staff to follow simple instructions, and an algorithm calculates bladder volume. Increasingly ultrasound (US) is a prerequisite in the placement of a catheter and decreases the dangers inherent in catheterisation where the diagnosis of retention is in doubt.
- A bladder volume on ultrasound ≥300 ml suggests urinary retention warranting decompression. However, the bladder ultrasound may be inaccurate due to body habitus, tissue oedema, or prior surgery and scarring. If the patient is in discomfort and unable to void, a urethral catheter should be placed regardless of the estimated volume on bladder ultrasound.
Acute Urinary Retention
Urology
Last Updated: 21st February 2022
Urinary retention is the inability to voluntarily urinate. Acute urinary retention is a medical emergency characterised by the abrupt development of the inability to pass urine (over a period of hours). Chronic urinary retention is the gradual (over months or years) development of the inability to empty the bladder completely, characterised by a residual volume greater than one litre or associated with the presence of a distended or palpable bladder.
Epidemiology
Acute urinary retention (AUR) is a common emergency. It is responsible for over 30,000 hospital admissions in the UK and many more visits to the emergency department. It has an incidence of 3/1000 patients each year. In 32,162 hospital episodes of AUR, 86% were in men and only 14% in females. 10% of men will have an episode of acute urinary retention between the ages of 70 and 75 years.
Causes
A variety of pathophysiologic mechanisms may be responsible for the development of AUR. The most common cause of urinary retention in men is benign prostatic hyperplasia.
- Outflow obstruction
- Urological causes of obstruction
- Benign prostatic hypertrophy (BPH)
- Bladder or prostate malignancy
- Urethral stricture
- Urethral/bladder stones
- Haematuria with clot retention
- Iatrogenic e.g. urinary stent occlusion
- Non-urological causes of obstruction
- Gravid uterus
- Pelvic organ prolapse
- Constipation/faecal impaction
- Abdominal/pelvic masses
- Urological causes of obstruction
- Neurological impairment with interruption to detrusor muscle innervation
- e.g. stroke, spinal cord lesions, diabetic nephropathy, multiple sclerosis
- Inefficient detrusor muscle plus a precipitating event resulting in an acute distended bladder
- e.g. postoperatively, excess alcohol
- Drugs
- e.g. anti-muscarinic and alpha-adrenergic medications
- Infection
- e.g. UTI, acute prostatitis, genital herpes, shingles, vulvovaginitis
- Trauma
- e.g. pelvic, urethral or penile trauma
Clinical features
- Presenting complaint
- Inability to pass urine
- Lower abdominal and/or suprapubic pain
- Confusion or agitation e.g. in older patients with dementia
- Examination
- A distended bladder arises from the pelvis and one is unable to get below it unlike other abdominal masses. It is usually midline fixed and dull to percussion. Huge bladders may rise above the umbilicus although this is unusual.
- Digital rectal examination (DRE) is mandatory not only to assess the prostate, but also to evaluate for masses, faecal impaction, perineal sensation and anal sphincter tone. It should be performed after catheterisation. The size, consistency and contour of the prostate gland should be documented.
- Neurological examination should include assessment of strength, sensation, reflexes, and muscle tone.
- Bladder scanning is increasingly available not only in the emergency department, but also on medical wards. These scanners allow staff to follow simple instructions, and an algorithm calculates bladder volume. Increasingly ultrasound (US) is a prerequisite in the placement of a catheter and decreases the dangers inherent in catheterisation where the diagnosis of retention is in doubt.
- A bladder volume on ultrasound ≥300 ml suggests urinary retention warranting decompression. However, the bladder ultrasound may be inaccurate due to body habitus, tissue oedema, or prior surgery and scarring. If the patient is in discomfort and unable to void, a urethral catheter should be placed regardless of the estimated volume on bladder ultrasound.
Further investigations
- U&Es to look for renal impairment
- FBC to look for anaemia and infection
- Urine dipstick for haematuria
- Renal ultrasound if any renal impairment is present
- N.B. Prostate specific antigen (PSA) measurement in this setting gives a high false positive rate and should be deferred by 2 weeks
Management
- Acute retention is painful and requires immediate treatment by catheterisation. Urethral catheterisation is the usual method employed in the UK.
- Suprapubic catheterisation (SPC) is usually reserved for when this fails. Suprapubic catheterisation is possible using several techniques. US guidance is an extremely useful adjunct to utilising either Bonanno catheters or the more conventional balloon catheter. Unguided SPC is contraindicated when there is a past history of bladder cancer, a history of haematuria or a suspicion of clot retention. These are the red flags of bladder cancer and one would wish to avoid seeding and spreading along the track that is used to insert the catheter.
- It's important to document post catheterisation residual volume (RV), features of prostate examination, renal function, catheter type and gauge (14 or 16 French gauge) and ease of introduction in the case notes, as they assist in determining further management. Consent should be recorded in the notes.
- Post obstructive diuresis can be a problem after relief of retention. Some patients can pass as much as 8-20 L/day. Cardiac failure or renal insufficiency patients, especially if they have marked peripheral oedema, are at high risk. Severe dehydration and postural hypotension can occur. Hourly urine outputs must be recorded and should be less than 200 ml/h as a general rule. High risk patients for this condition are often found to have a RV>1000 ml and impaired renal function.
- AUR secondary to constipation, UTI with no previous urinary tract symptoms and postoperative pain does not need follow up. Trial without catheter (TWOC) may be attempted. Although the role of early TWOC is debated, in these conditions it may be feasible with a residual volume of less than one litre. However, referral to a urology clinic with a catheter in situ is advised for most patients. BPH features may be an indication to prescribe alpha blockers although this is often determined by local protocols.
- Contraindications to discharge are renal impairment, significant post obstruction diuresis (e.g. RV > 1000 ml), sepsis, frank haematuria, dehydration, and inability to manage at home e.g. dementia. These patients will require hospital admission and inpatient urology input.
Report A Problem
Is there something wrong with this question? Let us know and we’ll fix it as soon as possible.
Loading Form...
- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
