Urinary retention

Key takeaways

Urinary retention belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Urinary retention to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Urinary retention from memory before moving on to harder problems.

Reference excerpt

Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When it is of sudden onset, symptoms include an inability to urinate and lower abdominal pain, while symptoms accompanying gradual onset may include loss of bladder control, mild lower abdominal pain, and a weak urine stream. About 7 per 100,000 of the general population are affected annually, and those with long-term urinary retention are at risk of urinary tract infections. Causes include blockage of the urethra, nerve problems, certain medications, and weak bladder muscles. Blockage can be caused by benign prostatic hyperplasia (BPH), urethral strictures, bladder stones, a cystocele, constipation, or tumors. Nerve problems can occur from diabetes, trauma, spinal cord problems, stroke, or heavy metal poisoning. Medications that can cause problems include anticholinergics, antihistamines, tricyclic antidepressants, cyclobenzaprine, diazepam, nonsteroidal anti-inflammatory drugs (NSAID), stimulants, and opioids. Diagnosis is typically based on measuring the amount of urine in the bladder after urinating. Treatment is typically with a catheter either through the urethra or lower abdomen. Other treatments may include medication to decrease the size of the prostate, urethral dilatation, a urethral stent, or surgery. Males are far more often affected than females, at a ratio of 13:1, in particular because of their possession of a prostate gland but also because their urethra is more susceptible to strictures, as it is far longer than the female one. In men, acute urinary retention is usually secondary to BPH. In males over the age of 40 about 6 per 1,000 are affected a year; among males over 80 this proportion increases to 30%.

Signs and symptoms Onset can be sudden or gradual. When the onset is sudden, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladder control, mild lower abdominal pain, and a weak urine stream. Those with long-term problems are at risk of urinary tract infections.

Complications

Acute urinary retention is a medical emergency and requires prompt treatment. The pain can be excruciating when urine is not able to flow out. Moreover, one can develop severe sweating, chest pain, anxiety and high blood pressure. Other patients may develop a shock-like condition and may require admission to a hospital. Serious complications of untreated urinary retention include bladder damage and chronic kidney failure. Urinary retention is a disorder treated in a hospital, and the quicker one seeks treatment, the fewer the complications. In the longer term, obstruction of the urinary tract may cause:

Bladder stones Atrophy of the detrusor muscle (atonic bladder is an extreme form) Hydronephrosis (congestion of the kidneys) Hypertrophy of the detrusor muscle (the muscle that squeezes the bladder to empty it during urination) Diverticula (formation of pouches) in the bladder wall (which can lead to stones and infection)

Causes

Bladder Infection Detrusor sphincter dyssynergia Neurogenic bladder (commonly spinal cord damage, pelvic splanchnic nerve damage, cauda equina syndrome, pontine micturition or storage center lesions, demyelinating diseases, multiple system atrophy, genital herpes, or meningitis-retention syndrome) Iatrogenic (caused by medical treatment/procedure) scarring of the bladder neck (commonly from removal of indwelling catheters or cystoscopy operations) Damage to the bladder

Prostate Benign prostatic hyperplasia (BPH) Prostate cancer and other pelvic malignancies Prostatitis

Penile urethra Congenital urethral valves Phimosis or pinhole meatus Circumcision Obstruction in the urethra, for example a stricture (usually caused either by injury or STD), a metastasis or a precipitated pseudogout crystal in the urine Pseudodyssynergia STD lesions (gonorrhoea causes numerous strictures, leading to a "rosary bead" appearance, whereas chlamydia usually causes a single stricture) Emasculation

Postoperative Risk factors include

Age: Older people may have degeneration of neural pathways involved with bladder function and it can lead to an increased risk of postoperative urinary retention. The risk of postoperative urinary retention increases up to 2.11 fold for people older than 60 years. Medications: Anticholinergics and medications with anticholinergic properties, alpha-adrenergic agonists, opiates, nonsteroidal anti-inflammatories (NSAIDs), calcium-channel blockers and beta-adrenergic agonists, may increase the risk. Anesthesia: General anesthetics during surgery may cause bladder atony by acting as a smooth muscle relaxant. General anesthetics can directly interfere with autonomic regulation of detrusor tone and predispose people to bladder overdistention and subsequent retention. Spinal anesthesia results in a blockade of the micturition reflex. Spinal anesthesia shows a higher risk of postoperative urinary retention compared to general anesthesia. Benign prostatic hyperplasia: Men with benign prostatic hyperplasia are at an increased risk of acute urinary retention. Surgery related: Operative times longer than 2 hours may lead to an increased risk of postoperative urinary retention 3-fold. Postoperative pain.

Chronic Chronic urinary retention that is due to bladder blockage which can either be as a result of muscle damage or neurological damage. If the retention is due to neurological damage, there is a disconnect between the brain to muscle communication, which can make it impossible to completely empty the bladder. If the retention is due to muscle damage, it is likely that the muscles are not able to contract enough to completely empty the bladder. The most common cause of chronic urinary retention is BPH.

Other Tethered spinal cord syndrome. Psychogenic causes – psychosocial stresses, fear associated with urination, paruresis ("shy bladder syndrome") – in extreme cases, urinary retention can result. noradrenergic drugs, that includes tricyclic antidepressants, as well as duloxetine, reboxetine, atomoxetine, venlafaxine, and stimulants, such as methylphenidate, amphetamine and MDMA. Use of NSAIDs, or drugs with anticholinergic properties. Stones or metastases, which can theoretically appear anywhere along the urinary tract, but vary in frequency depending on anatomy. Muscarinic antagonists such as atropine and scopolamine. Malfunctioning artificial urinary sphincter.

Diagnosis

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Urinary retention

Start with the simplest possible case. Write down what Urinary retention claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Urinary retention before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Urinary retention ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Urinary retention

In research: Urinary retention appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Urinary retention in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Urinary retention is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acute pain, Symptoms and signs: Urinary system, so understanding it makes those chapters shorter.
In everyday life: Look for Urinary retention outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Urinary retention in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Urinary retention means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Urinary retention out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Urinary retention in simple terms?

Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual.

Why does Urinary retention matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Urinary retention?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Urinary retention.