Lower Urinary Tract Emergencies

Chapter 3

Lower Urinary Tract Emergencies

David Thurtle and Suzanne Biers1, 3, 4, 5 / Alexandra Colquhoun2


Acute urinary retention (AUR) is the painful inability to pass urine (void). It is followed by relief of pain on catheterisation with good urine volume output.

Chronic urinary retention (CUR) is less well defined, but importantly is not painful and the patient continues to void (this may or may not be ‘normal’ voiding). Older definitions described a palpable/percussable bladder after voiding. The National Institute for Health and Care Excellence (NICE) defines CUR as a post-void residual volume of >1000ml (other definitions suggest smaller volumes and in fact any patient that does not empty their bladder completely might be considered to be retaining urine).

Acute or chronic urinary retention is a new inability to pass urine on a background of CUR.

Anuria is defined as the passage of less than 50ml urine in 1 day. Provided obstruction has been excluded, it is a sign of acute kidney injury (AKI), and requires medical referral and input (see Chapter 2).

Acute urinary retention

AUR is much more common in men than women. Between 4% and 7% of men will experience AUR at some point in their life. Although prostatic pathology is by far the most common, AUR has numerous causes.Broadly, AUR is due to either obstruction to the urine leaving the bladder or reduced/ineffective bladder contractility. The most common causes of bladder outlet obstruction (BOO) in men are shown in Box 3.1, and in women in Box 3.2. Causes of reduced bladder contractility can be similar in both sexes (Boxes 3.3 and 3.4). AUR can also be classified as ‘spontaneous’ or ‘precipitated’. Spontaneous retention is something of a misnomer as there remains a cause, often benign prostatic enlargement, but the term is used when no obvious precipitating cause is found.

Box 3.1 Male causes of BOO.

Benign prostatic enlargement (BPE).

Malignant enlargement of the prostate.

Urethral stricture.

Clot retention.

Urethral stone.

Urinary tract infection (UTI)/prostatitis.



Box 3.2 Female causes of BOO.

Pelvic organ prolapse.

Urethral stricture.

Clot retention.

Urethral diverticulum.

After stress incontinence surgery.


Fowler’s syndrome (impaired sphincter relaxation).


Pelvic mass/tumour.


Box 3.3 Causes of reduced bladder contractility.

Drugs (see Box 3.4).

Episode of overdistension of bladder.

Sacral or cauda equina nerve compression or injury.

Supra-sacral spinal cord injury.

Pelvic surgery/pelvic fracture (due to autonomic nerve damage).


Multiple sclerosis.

Diabetes mellitus (sensory and motor dysfunction).

Post-operative (immobility/anaesthetic agents/analgesics/epidural/pelvic or abdominal surgery).


Classically, patients report suprapubic pain and an inability to pass urine, which may be associated with a recent onset or deterioration of urinary symptoms. A full urological history will help to define the cause, once the retention has been drained.


Duration of onset (usually hours).

Preceding lower urinary tract symptoms (LUTS): patients usually describe worsening symptoms over days.

Any fever or dysuria (indicates infective cause).

Precipitating factors (constipation, general anaesthesia, recent surgery, e.g. haemorrhoidectomy, inguinal hernia, orthopaedic surgery).

Associated flank pain or a history of nocturnal incontinence (may suggest high pressure chronic retention causing hydronephrosis).

Ask about back pain and neurological symptoms.

Any visible haematuria.

Drug history: recent new medications (e.g. drugs with anticholinergic effects can cause urinary retention directly or by causing constipation), medication acting on the prostate to relieve bladder outflow obstruction, anticoagulant medication (must be considered if suprapubic catheter insertion is needed).

Previous medical history: history of pelvic or prostate cancer, post-menopausal bleeding (may indicate pelvic pathology in females), any recent urinary tract surgery.

Box 3.4 Pharmacological agents increasing the risk of urinary retention.





Hyoscine butylbromide.





Oral decongestants.


Antiparkinsonian agents.

Muscle relaxants.

Opioid analgesics.


AUR patients are in obvious discomfort.

Tender, palpable, percussable bladder suprapubically.

Digital rectal examination (after emptying the bladder) to assess the prostate size and contour for cancer, and assess for constipation or rectal masses.

Assess neurology, anal tone and peri-anal sensation if indicated.

Bimanual vaginal exam to assess for pelvic masses.


A handheld bladder ultrasound scan (USS) may be useful to check the bladder volume if there is any uncertainty about the diagnosis.

Dipstick urinalysis +/- culture (following sterile catheter insertion, or suprapubic aspiration).

Check urea and electrolytes (U&E), full blood count (FBC), C-reactive protein (CRP) +/- blood cultures. Venous blood gas for urgent potassium level.

USS of the renal tract should be considered where upper tract dysfunction is suspected (e.g. elevated creatinine).

Magnetic resonance imaging (MRI) of the spine should be performed urgently if there are any concerns of acute spinal injury.

Prostate-specific antigen (PSA) blood test is deferred as it can be abnormally raised with AUR or by catheterisation.


In all cases of AUR, the first priority is urgent relief of retention. Attempt urethral catheterisation first (see page 151 ‘catheter skills’ for tips). If this is unsuccessful, request advice or assessment from a urologist who will have the expertise and access to alternative catheter types (e.g. curved tip catheters such as Coudé or Tiemann), flexible cystoscopy and guidewire insertion of a catheter +/- urethral dilatation. Suprapubic catheter insertion using ultrasound guidance is an alternative if there are no patient contraindications (see page 153). Use a urometer drainage bag that can accurately record urine output.

Record in the medical case notes the volume immediately drained from the bladder, and ask for urine output to then be recorded hourly initially to exclude diuresis. Further management depends on the underlying cause of retention as outlined below.

Benign prostatic enlargement

Immediate: start an alpha-blocker (tamsulosin 400µg daily). A trial without catheter (TWOC) can be considered after 2–3 days, though it is not always successful (Box 3.5).

Delayed: additional drugs (e.g. 5-alpha-reductase inhibitors, Box 3.6) can be added if there is a persistent failure to void or persistent obstructive voiding symptoms after the catheter is removed. Finasteride, a 5-alpha-reductase inhibitor (5-ARI), reduces the volume of the prostate by about 25% but it takes many months before a patient derives its maximal clinical effect. Most men who fail to void after catheter removal will be considered for bladder outflow surgery such as a transurethral resection of the prostate (TURP) (Figure 3.1) or holmium laser enucleation of the prostate (HoLEP) (Figure 3.2). Clean intermittent self-catheterisation (CISC) or a long-term indwelling catheter are alternatives. In exceptional circumstances, e.g. medically unfit patients, a further attempt at catheter removal may be attempted after several months of treatment with a 5-ARI.

Box 3.5 Rates of recurrence of retention in men.

Precipitated retention

Once the precipitant is treated/removed, it is uncommon to get a second episode unless underlying risk factors are present.

Delaying TWOC to 7 days can increase the chance of success.

‘Spontaneous’ retention

50% recurrence within 1 week.

70% within 1 year (without treatment).

Retention related to BPE

60% of men treated with 1–3 days of an alpha-blocker were able to void spontaneously post-TWOC, compared to 38% on placebo1.

Recurrent acute retention incidence is 31% lower in those treated with an alpha-blocker1.

Box 3.6 Medication for BPH.

Alpha-blockers (tamsulosin/alfuzosin):

Block alpha-1 adrenergic receptors in smooth muscles, including in the prostate.

Patients should be warned of retrograde ejaculation or ‘dry orgasm’.

Can cause hypotension and dizziness, although tamsulosin is the most selective to prostatic α-1a adrenergic receptors.

Onset of action within days.

5-alpha-reductase inhibitors (finasteride/dutasteride):

Block the enzyme that converts testosterone to more potent androgens (dihydrotestosterone/DHT), which are promoters of prostatic growth.

Takes up to 6 months for maximal therapeutic benefit.

May negatively affect sexual function (loss of libido and impotence).

Will half PSA levels after 6 months.


Figure 3.1 Surgical option for treating bladder outlet obstruction in men. Intra-operative images of transurethral resection of the prostate (TURP). Surgeon operating with a monopolar TURP resecting loop (a), roller-ball diathermy (b), evacuation of prostatic chips with an Ellik evacuator (c).


Figure 3.2 Surgical option for treating bladder outlet obstruction in men. Intra-operative pictures of holmium laser enucleation of the prostate (HoLEP). The plane of the prostatic capsule is being developed (a). Laser incision through the hyperplastic prostate with the bladder visible above (b). Note how little haemorrhage is evident. (Images courtesy of Mr Tev Aho.)

Clot retention

Immediate: 3-way catheter (>20 Fr) insertion, bladder washout and saline irrigation. Treat any related cause (i.e. check for and treat abnormal clotting; treat any infection) (see page 52 for haematuria).

Delayed: haematuria needs full investigation with flexible cystoscopy under local anaesthesia when the urine is clear, imaging of the urinary tract (USS urinary tract or computed tomography [CT] urogram) and often urine cytology also.

Urethral stricture

Immediate: often it is not evident the patient has a stricture until it is difficult to pass a urethral catheter. In the emergency setting, urologists will often still attempt gentle catheterisation with a smaller calibre and stiffer material device (such as a silicone 12 Fr catheter), although any force should be avoided as this can cause false passages in the urethra. If this fails, alternative techniques include urethral dilatation and insertion of a urethral catheter or insertion of a suprapubic catheter.

Delayed: formal urethral dilatation under anaesthesia, optical urethrotomy (opening up of urethral stricture using a fine blade) or urethroplasty (excision of stricture and reconstruction of the urethra, sometimes using the buccal mucosa of the cheek as graft tissue).


Management is discussed on page 61. If the patient has had recent instrumentation/surgery, give prophylactic antibiotics to cover catheter insertion.


Treat with either suppositories or enemas and oral laxatives. Remember, constipation may be a sign of a neurological pathology. Attempt TWOC after the bowels have been fully evacuated.


Remove or treat the offending cause.

Do not miss neurological injuries: consider cauda equina syndrome (see page 121 for neurological topics).

Chronic urinary retention

Patients with CUR are less likely to present to the emergency department. However, a grossly enlarged bladder is not an uncommon finding in a primary care doctor’s surgery or in the urology outpatient department. The patient may be referred for acute or elective hospital review due to a palpable bladder or develop acute on chronic urinary retention and present as an emergency.

CUR can be subdivided into low-pressure or high-pressure conditions. Low-pressure CUR is caused predominantly by primary detrusor (bladder muscle) failure and does not tend to cause obstructive uropathy. In high-pressure CUR (HPCUR) the detrusor attempts to compensate for the increased outflow resistance with hypertrophy. A thickened, fibrous, trabeculated bladder wall develops over time, resulting in a raised intravesical pressure leading to hydronephrosis (Figure 3.3) and bladder diverticula. When detrusor pressure can no longer overcome the obstruction to voiding or there is an acute precipitating event, patients may present with acute on chronic retention.


Figure 3.3 A male patient presenting with urinary retention and acute kidney injury. Axial non-contrast computed tomography (CT) images (a) of the kidneys showing bilateral hydronephrosis, and (b) of a full bladder with dilated distal ureters (white arrows) with widely patent vesicoureteric junctions; (c) sagittal CT image showing a large-volume bladder extending nearly up to the umbilicus due to a large prostate (asterisk).


Nocturnal enuresis (incontinence at night whilst asleep), as the bladder pressure exceeds the relaxed urethral pressure overnight.

LUTS, especially nocturia and sensation of incomplete bladder emptying.

Sensation of abdominal bloating/fullness.

Patients with HPCUR may report a history of hypertension, renal impairment or congestive cardiac failure.

Recurrent UTIs as a result of urinary stasis.

Bilateral flank pain may suggest HPCUR.


As per AUR – renal function, residual volume measurement and urgent upper tract imaging are particularly important in HPCUR. Note, it is not uncommon for hydronephrosis to persist for some time after decompression of the bladder. Improving renal function should provide reassurance, and an USS may be repeated after several days to assess resolution.




Monitor urine output closely. Greater than 200ml urine output per hour for >2–4 hours suggests post-obstructive diuresis (see further management below).

Post-decompression haematuria is not uncommon. This is usually a self-limiting condition, only requiring treatment if severe and causing clot retention. A silicone catheter or wide-bore urethral catheter (i.e. 16 Fr or 18 Fr) can be used pre-emptively as these are less likely to become blocked and can be more easily flushed in the event of post-decompression bleeding.


HPCUR patients should not have a TWOC and will require bladder outlet surgery if they are fit enough. A long-term catheter will be required otherwise.

‘Low-pressure’ CUR patients often require urodynamic studies to guide treatment. Bladder outlet surgery is generally not effective for patients with detrusor failure as the bladder cannot generate a sufficient contraction to expel urine. Instead these patients require bladder drainage via an intermittent or indwelling catheter.

Post-obstructive diuresis

Post-obstructive diuresis is thought to result from the physiological excretion of the chronically retained urea, sodium and water. Furthermore, the corticomedullary gradient is lost in the obstructed kidney and the kidney is unable to immediately adjust when the obstruction is relieved. This diuresis may also be indicative of a persistent tubular dysfunction with an inadequate response to antidiuretic hormone (ADH).


Requires admission and observation.

Hourly urine output.

Daily U&E initially (watch for hyponatraemia).

Daily weights.

Lying/standing blood pressure (BP) (to assess for significant postural drop).

Supplement with intravenous (IV) fluids (usually saline) if there is inadequate oral intake. Overall, aim to replace fluids at around 50% of the previous hour’s urine output.

U&E should be repeated over the following weeks and months to ensure recovery in renal function.

Retention with catheterisable stomas

Patients with catheterisable stomas, such as Mitrofanoffs (appendix used as a catheterisable vesicocutaneous channel as an alternative route to perform clean intermittent self-catheterisation [CISC]) may present with retention due to failure to insert a catheter into the channel to drain the bladder. Urology input is required. It is reasonable for a urologist to attempt gentle catheterisation, with plenty of anaesthetic lubricant jelly and a small-calibre catheter (10–12 Fr guided by the patient’s usual catheter size). If this fails, enlist help from interventional radiology, who can try passing a hydrophilic guidewire under fluoroscopic guidance, perform gentle dilation of the channel, and follow with Seldinger insertion of an open tip catheter over the wire (Figure 3.4). If the urethra is patent and accessible, a temporary urethral catheter can be placed to relieve acute retention.


Figure 3.4 A patient with a Mitrofanoff channel from the umbilicus to the bladder, who presented with difficulty performing self-catheterisation down the channel. Fluoroscopic images: (a) metal forceps pointing to the umbilical opening; (b) showing bladder filling along with a wire inserted through the Mitrofanoff; (c) with contrast medium injected along a tight Mitrofanoff channel; (d) with a pigtail catheter inserted through the Mitrofanoff into the bladder from emergency treatment of retention to assist bladder drainage.


It is not safe to remove the catheter of a patient with HPCUR (associated with renal impairment). These patients will require bladder outflow surgery or long-term catheterisation to avoid kidney damage.

Key Points

AUR is painful – drain the bladder urgently.

Always check biochemistry, record bladder volume and monitor early urine output.

Assess for reversible causes of retention and treat them.

Be vigilant for HPCUR and acute neurological conditions.


Haematuria is the presence of blood in the urine.

Haematuria is either appreciable to the naked eye, visible haematuria, or detectable on urine dipstick testing, non-visible haematuria (Table 3.1).

Table 3.1 Classification of haematuria.



Appreciable to the naked eye

Present on urine dipstick









Visible haematuria is an alarming symptom and often prompts emergency or urgent presentation to either primary or secondary care. Management and further investigation of haematuria is important as a high proportion of patients will have sinister or serious pathology accounting for the presence of blood in the urine.

Non-visible haematuria is defined as a positive urine dipstick measuring at least 1+ on the dipstick scale. ‘Trace’ dipstick haematuria is not considered significant and does not warrant further investigation. Urine microscopy is less sensitive than urine dipstick testing due to a high false-negative rate and is not recommended to determine the presence of non-visible haematuria.


Haematuria has many causes some of which are easily treatable (e.g. UTI) and some of which require more complex intervention (e.g. muscle-invasive bladder cancer). A comprehensive list of the causes of haematuria is shown in Table 3.2. The more common causes can be grouped as follows:

Urological malignancy, including bladder cancer (Figure 3.5), renal cancer (Figure 3.6) and prostate cancer.


Figure 3.5 Cystoscopic view of a solitary bladder cancer (a) and transurethral resection of the bladder tumour with a resectoscope using a wire loop (b).

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May 4, 2018 | Posted by in ABDOMINAL MEDICINE | Comments Off on Lower Urinary Tract Emergencies
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