OVERVIEW

What is Urinary Tract Obstruction?

The urinary system consists of the kidneys (left and right), ureters, bladder, and urethra. The kidneys and ureters are referred to as the upper urinary tract, while the bladder and urethra are called the lower urinary tract. When blood flows through the kidneys, it undergoes filtration and reabsorption, forming urine that drains into the corresponding ureter. The ureters then transport the urine to the bladder, which is eventually expelled through the urethra.

For normal and smooth urination to occur, all components of the urinary system must maintain proper structure and function.

Urinary tract obstruction, also known as urinary system obstruction, refers to conditions where diseases of the urinary system itself or surrounding organs lead to narrowing or complete blockage of the urinary passages, weakened or lost muscle contraction function, or impaired urine flow. This results in obstructed urine drainage from the proximal (upper) side of the blockage, causing dilation, fluid accumulation (hydronephrosis), and even kidney damage.

Urinary tract obstruction is a common condition with diverse causes and symptoms. Diagnosis relies on medical history, symptoms, physical examinations, and imaging tests such as ultrasound or CT. Treatment primarily focuses on addressing the underlying cause and relieving the obstruction.

What Are the Types of Urinary Tract Obstruction?

Urinary tract obstruction is a broad term encompassing various conditions, which can be classified as follows:

• By obstruction degree: Complete or partial. Complete obstruction means the urinary tract is entirely blocked, preventing urine flow, while partial obstruction allows some urine to pass.

• By obstruction speed: Acute or chronic. Acute obstruction occurs suddenly within a short period, whereas chronic obstruction develops gradually over a longer time.

• By obstruction location: Upper or lower urinary tract obstruction. Upper tract obstruction affects the kidneys and ureters, while lower tract obstruction involves the bladder and urethra.

SYMPTOMS

What are the common clinical manifestations of urinary tract obstruction patients?

Urinary tract obstruction can present with various clinical manifestations depending on the underlying cause, degree of obstruction, progression rate, location, and associated complications. Common symptoms include pain, hematuria, changes in urine output, and may also involve conditions such as hypertension or urinary tract infections with related symptoms. Specifically:

• Pain: Commonly seen in conditions like urinary calculi. The location and nature of pain vary depending on the site of obstruction. For example:

• Kidney stones often present as persistent dull pain in the affected renal area (commonly referred to as the lower back), which is usually tolerable.

• Ureteral stones typically manifest as renal colic (intermittent severe pain in the affected renal area, unrelieved by positional changes, possibly radiating to the ipsilateral abdomen or even the penis/scrotum, often unbearable).

• Bladder stones cause pain in the bladder area (lower abdomen), especially during urination, and may be accompanied by irritative symptoms like urgency and frequency.

• Urethral stones, resulting from bladder stones entering the urethra, present as sudden interruption of urine flow, pain radiating along the urethra to the glans penis, and urinary retention.

• However, urinary tract obstruction may also be asymptomatic, lacking noticeable pain, and may only be detected when severe hydronephrosis develops.

• Hematuria: Some causes of obstruction may lead to hematuria. For instance, urinary calculi can damage the mucosal lining, resulting in hematuria; benign prostatic hyperplasia may cause small vessel ruptures and bleeding; urothelial tumors often present with hematuria. However, the severity of hematuria does not correlate with the severity of the disease or the degree of obstruction.

• Changes in urine output: Complete urinary tract obstruction or impaired renal function may lead to anuria or oliguria.

What are the common complications in urinary tract obstruction patients?

Obstruction can lead to hydronephrosis, compression atrophy of renal parenchyma, and reduced blood supply, potentially causing hypertension. Bacterial invasion and proliferation are more likely when obstruction occurs, leading to infections that may manifest as high fever and chills. In severe cases, it may even trigger urosepsis, which can be life-threatening.

CAUSES

What are the common causes of urinary tract obstruction?

Urinary system obstruction has diverse causes, including diseases of the genitourinary organs or adjacent structures. Common conditions leading to urinary tract obstruction include:

• Urinary calculi: such as kidney stones, ureteral stones, bladder stones, or urethral stones;

• Urinary tract tumors: including renal or renal pelvis tumors, ureteral tumors, bladder tumors, urethral cancer, penile cancer, and prostate cancer;

• Congenital abnormalities of the urinary system: such as ureteropelvic junction obstruction, ectopic ureteral orifice, or ureterocele;

• Post-traumatic or inflammatory strictures: such as urethral strictures after injury or ureteral strictures following inflammation;

• Benign prostatic hyperplasia (BPH): common in elderly males;

• Invasion or compression by adjacent organ diseases: primarily gynecological or gastrointestinal tumors, such as cervical cancer, ovarian cancer, or colorectal cancer compressing or invading the ureters, bladder, or urethra;

• Neurological disorders: such as cerebral hemorrhage, cerebral infarction, spinal cord injury, or diabetes causing neuropathy, mainly affecting bladder function or bladder-sphincter coordination;

• Others: iatrogenic injuries during urological or adjacent surgeries may impair urinary tract patency, and procedures like cervical cancer radiotherapy also carry a risk of causing obstruction.

Although urinary obstruction has many causes, the common conditions vary by age group. Congenital abnormalities predominate in children, urolithiasis is more frequent in young adults, while elderly patients commonly experience BPH, tumors, or stones.

DIAGNOSIS

What Tests Are Needed to Diagnose Urinary Tract Obstruction?

Different examination methods have their own advantages and disadvantages, and multiple tests are often required to confirm a diagnosis:

• Renal Function + Electrolytes: A blood test that primarily measures creatinine, blood urea nitrogen, serum cystatin C, potassium, sodium, and other indicators to assess the extent of kidney damage. Here, renal function refers to the overall function of both kidneys. Therefore, if both kidneys are affected by obstruction but the impact is mild or short-term, or if one kidney has completely lost function due to upper urinary tract obstruction while the other remains normal, these indicators may still appear normal. Lower urinary tract (bladder and urethra) obstruction can affect both kidneys, but due to the bladder's buffering effect, renal insufficiency may appear later.

• Urinalysis: Typically performed on a random urine sample. It is convenient, inexpensive, and fast, and can detect white blood cells, red blood cells, protein, and urine pH. While it does not directly diagnose urinary tract obstruction, it is essential for assessing infection or hematuria.

• Urinary System Color Doppler Ultrasound: A simple, non-invasive, and bedside-friendly examination, though it can be affected by intestinal gas and operator experience. Patients are advised to hold their urine before the test. It serves as a preliminary diagnostic tool for urinary tract obstruction to guide further treatment. Ultrasound can detect most causes such as stones or tumors and measure residual urine volume in cases of urinary retention.

• CT Scan: Involves radiation exposure and is more expensive. It is typically used as a follow-up test after ultrasound.

• MRI: Compared to CT, MRI has its own pros and cons. It takes longer and is less effective for visualizing stones but can clearly display hydronephrosis and partially replace contrast imaging.

• Intravenous Pyelography (IVP): A contrast agent is injected intravenously and excreted by the kidneys to visualize the urinary tract. It assesses both urinary tract morphology and kidney function. However, the procedure is relatively complex, cannot evaluate surrounding anatomy, and fails to produce images if one kidney is severely impaired. Since the contrast agent may affect renal function, this test is contraindicated in cases of abnormal overall kidney function.

• Radionuclide Renal Imaging or Renogram: Involves intravenous injection of a radioactive tracer to monitor kidney excretion, allowing relatively precise assessment of each kidney's function.

Diagnosis of urinary tract obstruction primarily relies on imaging. The above tests generally suffice for initial diagnosis. However, further examinations may be needed to clarify the condition—for example, cystoscopy for bladder tumors or urodynamic studies for benign prostatic hyperplasia. If urinary obstruction is suspected to result from other systemic diseases, consultation with the relevant specialist is required.

TREATMENT

Which department should be consulted for urinary tract obstruction?

Urinary tract obstruction often requires initial consultation in the emergency department, urology, or nephrology. After identifying the cause, appropriate treatment is provided. If complications arise or the cause is related to other systemic diseases (e.g., gynecological tumors, cerebral hemorrhage, pelvic fractures), consultation with or referral to the relevant specialty is necessary.

How should urinary tract obstruction be treated?

The first step in treating urinary tract obstruction is to preliminarily determine the cause. Once identified, measures should be taken to relieve the obstruction, drain urine, or restore urinary tract patency based on the condition.

If the patient's condition temporarily does not allow targeted treatment for the underlying cause, severe lower urinary tract obstruction often requires catheterization or cystostomy. For bilateral upper urinary tract obstruction or obstruction in a solitary kidney, emergency ureteral retrograde intubation or nephrostomy is necessary to ensure at least one side of the upper urinary tract remains unobstructed. In critical cases where kidney function is severely impaired and life-threatening, hemodialysis may be required.

These measures can prevent further kidney damage and buy time for diagnosis and treatment. Once the patient's condition stabilizes, further examinations and targeted treatments can be performed.

How to determine whether kidney function can recover?

Whether kidney function recovers in cases of complete or partial obstruction depends mainly on the degree and duration of the obstruction, with no definitive standard currently available.

Currently, the absence of kidney visualization on radionuclide scans and significant cortical thinning observed in imaging studies are considered poor prognostic factors.

DIET & LIFESTYLE

What should patients with urinary tract obstruction pay attention to in daily life?

• Adjust water intake according to the condition;

• For patients with impaired renal function, when medications are needed to treat other diseases, weigh the pros and cons and choose drugs with minimal impact on renal function. Some medications require dosage adjustments based on renal function status;

• Seek diagnosis, treatment, and follow-up examinations at正规医院 (regular hospitals). Self-treatment with folk remedies is not recommended.

PREVENTION

How to Prevent Urinary Tract Obstruction?

Urinary tract obstruction itself cannot be prevented, but measures should target the underlying conditions that cause it. For example, drinking plenty of water can prevent stone formation, quitting smoking and alcohol may reduce tumor risks, and practicing safe sex or using condoms helps avoid urethral infections.