OVERVIEW

What is urinary retention?

Urinary retention refers to the inability to fully or partially empty the bladder after urination, leading to the accumulation of urine in the bladder. It most commonly occurs in elderly men.

The most typical symptoms include the inability to urinate and a feeling of fullness or pressure in the lower abdomen. During a medical examination, a doctor may palpate a firm, well-defined, and tense mass in the lower abdominal area (which is actually the urine-filled bladder).

How is urinary retention treated?

The primary treatment involves restoring urine flow, with catheterization being the preferred method.

Is urinary retention common? Who is most at risk?

This condition is relatively common in urological emergencies. It primarily affects elderly men with benign prostatic hyperplasia (BPH), especially those over 60 years old. Alcohol consumption or colds can also trigger it, while it is relatively rare in women.

What is the bladder? What is its function?

The bladder, commonly known as the "urinary bladder," is an organ primarily responsible for storing urine. It has a certain degree of elasticity, allowing it to change in size and shape as urine volume fluctuates. It connects to the bilateral ureters above and the urethra below, located in the midline of the lower abdomen.

How is urination formed?

The physiological process of urination mainly involves the contraction and relaxation of the detrusor muscle of the bladder and the sphincter (and pelvic floor muscles) at the bladder outlet. Only when these two work in coordination can comfortable urination occur—neither difficulty in voiding nor uncontrollable, involuntary urination.

SYMPTOMS

What clinical manifestations can patients with urinary retention have?

Based on the speed of onset, it can be classified as acute or chronic, including:

• Acute urinary retention: Sudden onset, occurring abruptly, mainly presenting as severe distension and pain in the lower abdomen (bladder area), a strong urge to urinate but inability to pass urine, occasionally passing small amounts with no symptom relief.

• Chronic urinary retention: Gradual onset, slowly progressing over a long period, often unnoticed. Symptoms resemble those of prostate hyperplasia, such as frequent urination, incomplete voiding, and difficulty urinating, but usually without severe lower abdominal distension or pain.
  In rare cases, some individuals may experience no obvious discomfort, yet urinary retention has already caused bilateral ureteral dilation, hydronephrosis, kidney damage, nausea, vomiting, etc.

CAUSES

What are the possible causes of urinary retention?

Normally, the bladder serves as an organ for storing urine, and urine must pass through the urethra to be expelled from the body. Therefore, bladder diseases or urethral-related conditions can lead to urinary retention.

There are many causes of this condition, which are mainly categorized into mechanical and dynamic factors, with mechanical causes being the most common.

• Mechanical causes: These involve narrowing or complete blockage of the urinary excretion pathway due to various reasons. Common examples include:

  • Bladder neck diseases, such as bladder neck contracture;
  • Prostate diseases, such as benign prostatic hyperplasia, prostate tumors, or acute prostatitis;
  • Congenital urethral diseases, such as congenital posterior urethral valves;
  • Acquired urethral diseases, such as urethral stones, urethral foreign bodies, urethral strictures from various causes, urethral and penile trauma, or urethral infections;
  • Compression from diseases of surrounding organs leading to urethral obstruction, such as cervical cancer invading the urethra or pelvic tumors. Among these, benign prostatic hyperplasia is the most common.

• Dynamic causes: The primary driving force for bladder emptying is the contraction of the detrusor muscle, which is controlled by nerves. Any condition that impairs or prevents detrusor muscle contraction falls under dynamic urinary retention. Common causes include:

  • Central or peripheral nervous system diseases, such as spinal cord injuries or diabetes;
  • Surgical damage to the innervating nerves, such as rectal or gynecological surgeries;
  • General or spinal anesthesia;
  • Use of certain medications, such as atropine or 654-2.

DIAGNOSIS

What tests are needed for urinary retention?

Diagnosing urinary retention alone is relatively easy, but identifying the underlying cause is slightly more complex. The main diagnostic approaches include:

• Medical history inquiry: A detailed medical history is crucial for accurate diagnosis and identifying the cause. It mainly involves changes in symptoms, history of trauma, smoking and alcohol use, medication history, etc. Patients must not withhold information from the doctor.

• Physical examination: Extremely important. In cases of acute urinary retention with a certain volume, a firm, well-defined, and tense mass can be palpated in the lower abdomen, sometimes mistaken for a tumor. Palpation may cause tenderness and a stronger urge to urinate.
  For severe chronic urinary retention, due to long-term bladder decompensation and loss of normal contraction and relaxation functions, physical signs may not be obvious even when the bladder contains a large amount of urine.

• Digital rectal examination: Required for both men and women. It can assess the presence of masses and evaluate anal sphincter muscle strength. If central nervous system damage is suspected, a neurological examination—including muscle strength, muscle tone, and reflexes—should also be performed.

• Urinalysis and urine culture + sensitivity test: If the patient can pass a small amount of urine, a sample should be collected for testing to better determine the presence of white blood cells or red blood cells in the urine, avoiding the influence of catheterization, especially for red blood cells.
  If the patient is completely unable to urinate, a sample can only be collected after catheterization. Urinalysis and urine culture + sensitivity tests are mainly used to confirm urinary tract infections, identify the causative bacteria, and guide antibiotic selection.

• Urinary tract ultrasound + post-void residual urine measurement: Used to assess the basic condition of the urinary tract and prostate, such as the presence of bladder stones or prostate size.
  After the examination, the patient is instructed to urinate, and the remaining urine volume in the bladder is measured as the post-void residual urine.
  However, in cases of acute urinary retention with severe symptoms, the patient may not even cooperate with the ultrasound examination. Emergency catheterization is often required, which can also measure residual urine. Catheter-based residual urine measurement is more accurate than ultrasound.

• CT scan: A urinary tract CT scan can clarify urinary system conditions, such as the presence of bladder stones or an approximate estimation of retained urine volume. For urinary retention suspected to be caused by neurological conditions like cerebral infarction, a cranial CT scan is necessary.

• Kidney function and PSA tests: Both are blood tests. Abnormal kidney function is mainly seen in chronic urinary retention, while acute urinary retention alone usually shows normal kidney function. PSA is used to assess prostate cancer, but it may be elevated due to urinary retention.

TREATMENT

Which department should be consulted for urinary retention?

For urinary retention, patients should visit the emergency department or urology department. If it is accompanied by conditions such as cerebral infarction or cervical cancer, consultation with neurology, gynecology, etc., may also be necessary.

How should urinary retention be treated?

• Acute urinary retention: The treatment principle is to identify and address the underlying cause to restore normal urination. For severe cases, the priority is to relieve symptoms and restore urination. The preferred method is transurethral catheterization. If catheterization fails, temporary relief can be achieved through suprapubic bladder puncture with a thick needle or suprapubic cystostomy. Further tests to determine and treat the underlying cause should follow once symptoms improve. If the cause cannot be treated, long-term catheterization or cystostomy may be required.

• Chronic urinary retention: If urinary retention leads to bilateral hydronephrosis and impaired kidney function, bladder drainage should be performed first. Once hydronephrosis and kidney function improve, the underlying cause can be addressed. If the cause cannot be treated, long-term bladder drainage methods such as catheterization, cystostomy, or clean intermittent self-catheterization may be necessary.

What complications may occur in urinary retention patients with indwelling catheters?

• Hematuria: Often caused by bladder mucosal bleeding after rapid urine drainage, usually relieved by bladder irrigation.

• Hypotension: Typically transient and resolves on its own without special treatment.

• Post-obstructive diuresis: Mainly occurs in chronic urinary retention patients as a compensatory response of the body.

DIET & LIFESTYLE

What should patients with urinary retention pay attention to after catheterization?

• Drink plenty of water;

• Engage in appropriate physical activity;

• Bathing is allowed;

• Whether standing or lying down, the catheter should be positioned below the level of the bladder;

• The timing of catheter removal depends on the specific situation. For first-time cases caused by benign prostatic hyperplasia, removal may be attempted after one week. However, for those requiring long-term catheterization, it is generally recommended to replace it once a month;

• Long-term use of antibiotics is unnecessary and should be avoided.

PREVENTION

How to prevent urinary retention?

• Address causative factors promptly, such as urethral stricture or diabetes;

• Avoid potential triggers whenever possible, e.g., patients with prostate hyperplasia should abstain from alcohol and reduce spicy or irritating foods;

• Practice urinating in bed before surgery, and apply warm towel compresses to the lower abdomen postoperatively.