Ureteropelvic Junction (UPJ) Obstruction

What is Ureteropelvic Junction Obstruction?

Ureteropelvic junction (UPJ) obstruction is a condition in which there is a blockage or narrowing at the beginning of the ureter (the area where the kidney connects to the ureter). This narrowing prevents urine from flowing normally from the kidney to the ureter, causing increased pressure in the kidney that may eventually lead to kidney damage.

This condition can be congenital or acquired. Congenital UPJ obstruction is present at birth due to abnormal development of the ureter during embryogenesis, whereas acquired UPJ obstruction may develop following trauma, infection, stones, or surgical interventions.

Causes of UPJ Obstruction

UPJ obstruction is caused by a blockage or narrowing at the junction where the ureter meets the kidney. This impedes the normal flow of urine from the kidney to the ureter and can eventually lead to kidney damage. UPJ obstruction may be either congenital or acquired. Here are the main causes:

1. Congenital Causes

Congenital UPJ obstruction is present at birth and often arises during fetal development.

• Embryologic Developmental Abnormalities: The narrowing at the ureteropelvic junction typically results from abnormal development of the ureter during embryogenesis. This may occur due to improper formation of the muscular wall or insufficient dilation of the ureter.
• Vascular Causes: Nearby blood vessels that supply the kidney may compress the ureter if they pass in front of it, leading to an “anomalous crossing vessel” that causes narrowing.
• Renal Anomalies: Certain congenital renal anomalies can alter the structure of the ureter, contributing to obstruction at the junction.

2. Acquired Causes

Acquired UPJ obstruction develops later due to various factors, including:

• Kidney Stones: Stones in the kidney or ureter can lodge at the junction, impeding urine flow and causing narrowing.
• Trauma: External trauma (such as from an accident or prior surgery) to the kidney or ureter may result in scarring and subsequent narrowing.
• Subcutaneous Infections: Urinary tract infections, kidney infections, or inflammation can cause swelling and structural changes in the ureter, leading to obstruction.
• Surgical Interventions: Previous urological surgeries, especially those for kidney stones or kidney transplants, may result in scar tissue formation at the UPJ, causing narrowing.
• Hydronephrosis: Long-standing UPJ obstruction may lead to hydronephrosis (swelling of the kidney due to urine buildup), which further worsens the obstruction.

3. Genetic Factors

Sometimes, a familial predisposition can contribute to the development of UPJ obstruction.

Symptoms of UPJ Obstruction

UPJ obstruction hinders the passage of urine from the kidney to the ureter due to narrowing or blockage at the junction. This causes urine to back up and increases pressure in the kidney, leading to various symptoms. Common signs and symptoms include:

1. Kidney (Flank) Pain

• The most common symptom is kidney pain or flank pain, typically felt on one side in the flank area. This pain results from the increased pressure due to the blockage.

2. Hydronephrosis

• Hydronephrosis refers to the swelling of the kidney caused by the accumulation of urine. This can lead to pain, swelling, and eventual impairment of kidney function.

3. Urinary Tract Infections (UTIs)

• Obstruction of urine flow increases the risk of bacterial infections in the urinary tract, leading to symptoms such as painful urination, frequent urination, and cloudy or foul-smelling urine.

4. Hematuria (Blood in Urine)

• The increased pressure in the kidney may cause small bleeding within the urinary tract, which can manifest as blood in the urine.

5. Delayed Urination

• Difficulty initiating or completing urination due to the obstruction may be observed.

6. Loss of Kidney Function

• If the obstruction persists over time, kidney function may decline, eventually leading to kidney failure.

7. Nausea and Vomiting

• Due to the effects of hydronephrosis or declining kidney function, nausea and vomiting may occur.

8. Swelling in the Lower Back or Abdomen

• The enlargement of the kidney or accumulation of urine may cause noticeable swelling in the lower back or abdominal area.

Diagnosis of UPJ Obstruction

UPJ obstruction is diagnosed by evaluating the patient’s symptoms, medical history, and various imaging tests. Although early stages may not show marked symptoms, the condition can cause kidney damage over time. The primary diagnostic methods include:

1. Physical Examination

• Pain and Swelling: Patients presenting with suspected UPJ obstruction are examined for flank or abdominal pain and swelling.
• Urinary Tract Infections: Signs of infection such as fever or painful urination are also assessed.

2. Ultrasonography

• Prenatal Ultrasonography: Fetal hydronephrosis detected during prenatal ultrasound may be an early indicator of UPJ obstruction.
• Doppler Ultrasound: This method evaluates the degree of hydronephrosis and the level of obstruction by assessing urine flow and kidney enlargement.
• Assessment of Kidney Enlargement: Ultrasound provides visual data regarding kidney size and urine accumulation.

3. Computed Tomography (CT)

• Detailed Imaging: A CT scan helps visualize the structural changes and obstructions caused by UPJ narrowing, revealing increased pressure and blockage areas.
• Hydronephrosis Evaluation: CT can effectively assess the extent of urine accumulation in the kidney.

4. Mag3 Renography

• Kidney Function Test: This test evaluates kidney function. If urine flow is obstructed by UPJ narrowing, the kidney’s ability to process and excrete urine will be reduced.
• Degree of Obstruction: Mag3 renography helps measure the extent to which the kidney is affected and how much urine flow is impeded.

5. Intravenous Pyelography (IVP)

• Use of Contrast Agent: In IVP, a contrast dye is injected intravenously and images are taken along the urinary tract to visualize fluid accumulation and structural status.
• Obstruction and Dilation: This test visualizes the accumulation of urine, dilation of the kidney, and the degree of obstruction.

6. Retrograde Pyelography

• Visualization of the Ureter: In this procedure, a contrast dye is injected directly into the ureter and X-ray images are taken to pinpoint the exact location and size of the obstruction.

7. Laparoscopy or Endoscopy (if necessary)

• Surgical Inspection: When imaging tests are inconclusive or surgery is needed, laparoscopy or endoscopy allows direct visualization of the urinary tract.

8. Urine Tests

• Hematuria and Infection: Urinalysis can detect blood in the urine or signs of infection, supporting the diagnosis.

9. Genetic Tests

• Familial Predisposition: If a genetic cause is suspected, tests may be performed to determine whether there is a familial tendency for UPJ obstruction.

Complications of UPJ Obstruction

UPJ obstruction can lead to serious complications by impeding the flow of urine from the kidney to the ureter. If left untreated, it may cause irreversible kidney damage. Potential long-term complications include:

1. Hydronephrosis

• Definition: Hydronephrosis is the swelling of the kidney due to urine accumulation. It is the most common complication of UPJ obstruction, resulting from urine backup and increased kidney pressure.
• Effects: Kidney swelling can impair organ function and, if untreated, lead to kidney failure.

2. Loss of Kidney Function

• Functional Damage: Obstruction prevents normal urine output, potentially leading to gradual loss of kidney function.
• Consequences: Reduced kidney function can result in reproductive issues and may progress to kidney failure.

3. Urinary Tract Infections (UTIs)

• Bacterial Infections: The blockage increases the risk of UTIs, which can progress to severe infections like pyelonephritis if untreated.

4. Hematuria (Blood in Urine)

• Internal Bleeding: Elevated pressure can cause small blood vessels to rupture, resulting in blood in the urine.
• Complications: Hematuria may indicate infection or kidney damage and can worsen if not treated.

5. Kidney Stones

• Impaired Urine Flow: Obstruction can lead to concentrated urine and subsequent stone formation, which may further block urine flow and cause additional pain and infection.

6. Hypertension (High Blood Pressure)

• Kidney Damage and Elevated Blood Pressure: Increased kidney pressure may lead to fluid retention and, consequently, high blood pressure, which can affect heart and vascular health over time.
• Risk of Kidney Failure: Persistent high blood pressure can further damage kidney function.

7. Kidney Failure

• Chronic Kidney Failure: If UPJ obstruction is not corrected, progressive loss of kidney function may result in kidney failure, potentially requiring dialysis or a transplant.
• Severe Damage: This may lead to nearly complete loss of kidney function and life-threatening complications.

8. Reflux Nephropathy

• Urine Backflow: UPJ obstruction can cause urine to reflux back into the kidney, leading to inflammation and damage.
• Effects: This backflow may trigger infections and kidney inflammation, ultimately compromising kidney function.

9. Kidney Pain

• Persistent or Intermittent Pain: The blockage may cause continuous or cramp-like kidney pain due to increased pressure.
• Chronic Pain: Long-term obstruction can lead to chronic pain, negatively affecting quality of life.

10. Fetal Hydronephrosis

• Effects in Newborns: Fetal hydronephrosis due to UPJ obstruction is an important condition to monitor after birth as it can threaten kidney function and lead to long-term damage if untreated.

Treatment Options for UPJ Obstruction

UPJ obstruction, which impairs the passage of urine from the kidney to the ureter, endangers kidney function and requires treatment. The treatment options vary according to the patient’s age, the degree of obstruction, and the presence of complications. Here are the treatment methods:

1. Surgical Intervention

• Pyeloplasty
  • Description: Pyeloplasty is the most commonly used surgical method for treating UPJ obstruction. In this procedure, the obstructed segment at the ureteropelvic junction is excised and a new connection is created to restore normal urine flow.
  • Objective: The goal is to remove the blockage and reestablish proper urine drainage.
  • Techniques: This can be performed via open surgery, laparoscopic surgery, or robotic surgery, with modern minimally invasive approaches often preferred.
• Nephrectomy (Kidney Removal)
  • Description: If the kidney is severely damaged or nonfunctional, surgical removal of the kidney may be necessary. This is rarely required and is only considered when the kidney cannot be salvaged.

2. Endoscopic Methods

• Balloon Dilation
  • Description: This minimally invasive technique involves inserting a balloon into the obstructed area and inflating it to widen the narrowed segment.
  • Advantages: It is minimally invasive and often allows for a quicker recovery.
  • Disadvantages: This method may not be suitable for all patients and tends to have lower long-term success rates.
• Endoscopic Pyelotomy
  • Description: An endoscope is inserted into the obstructed region and the blockage is incised. This method is less invasive but is generally less effective than surgical intervention.
  • Indications: It may be applied in cases with minor obstruction.

3. Antibiotic Therapy

• Prevention of Urinary Tract Infections: Since UPJ obstruction can lead to recurrent UTIs, antibiotics may be used to prevent or treat infections.
• Temporary Measure: Antibiotics serve as a temporary solution to control infections until definitive surgical treatment is performed.

4. Treatments Supporting Kidney Function

• Monitoring Kidney Function: Regular follow-ups including ultrasound and urine tests are essential to ensure that kidney function is preserved.
• Diuretic Therapy: Diuretics may be used to increase urine flow from the kidney; however, this is typically a temporary measure.

5. Percutaneous Nephrostomy

• Description: In cases of severe urine buildup (hydronephrosis), a tube is inserted percutaneously to drain urine directly from the kidney. This is a temporary measure to stabilize the patient before definitive surgery.

6. Observation and Follow-up

• Mild Obstructions: If the obstruction is minimal and kidney function is maintained, the patient may be managed with careful observation without immediate surgery.
• Symptom Monitoring: Regular monitoring for pain, UTIs, or declining kidney function is essential, with intervention as needed.

7. Laparoscopic and Robotic Surgery

• Modern Techniques: These minimally invasive methods use small incisions to access the obstructed area, resulting in less pain, faster recovery, and shorter hospital stays.

Advantages: Less postoperative pain, quicker recovery, and reduced hospital stay.