Ureteropelvic Junction Obstruction - Causes, Symptoms, Diagnosis, and Treatment

Introduction:

The urinary system comprises kidneys, ureters, urinary bladder, and urethra. The kidneys are an important organ present in the urinary system and consist of three parts:

1. Renal cortex (site of filtration of blood).

2. Renal medulla (the urine gets formed here).

3. Renal pelvis (the funnel-shaped structure that transports the urine to the ureters).

Ureters are tube-like structures that allow the passage of urine from the kidneys to the urinary bladder. The muscles present within the ureters undergo contraction and relaxation (peristalsis) to propel urine towards the bladder. Ureteropelvic junction obstruction blocks the passage of urine from the renal pelvis to the ureters resulting in urinary retention within the kidneys.

What Is Ureteropelvic Junction Obstruction?

It is a condition in which blockage occurs at the meeting point of kidneys and ureters. After the urine formation gets complete in the renal medulla (part of the kidney), it is transferred to the renal pelvis. As a result, the urine flows through the renal pelvis to the ureters. The junction where the urine is transferred from the kidneys to the ureters is known as the ureteropelvic junction. If it gets obstructed, the urine backflows and accumulates, increasing pressure on the kidneys. This pressure can increase to an extent where it causes permanent damage to the kidneys. The condition can be present in an individual by birth (congenital) or acquired during the lifetime due to trauma, presence of a tumor or scar tissue, and narrowing of the ureters.

How Does the Urine Flow Normally?

Kidneys filter the blood and are responsible for the formation of urine. An important part of the kidney, the renal pelvis, drains the urine to the tubes known as ureters. The urine then travels from the ureters to reach the urinary bladder and finally outside the body through the urethra. There are two ureters present within the urinary system. Urine normally flows even if one of them is working fine. The problem arises when both get blocked and hinder the urinary flow. In addition, if the urine remains for a long time in the body, it provides a medium for bacterial growth, thereby causing infection of the urinary tract.

What Are the Causes of Ureteropelvic Junction Obstruction?

Ureteropelvic junction obstruction can be present since birth or occur during the lifetime of an individual. If the condition is present by birth, the following may be the causes:

• Underdeveloped Ureters: There is a layer of smooth muscles present within the ureters that contract and relax them to allow urine flow. If the ureters are incompletely developed by birth, the order of arrangement of the smooth muscle layer gets disturbed. As a result, the urine does not get drained from the kidneys to the ureters.

• High Insertion of the Ureters: The ureters are directly attached to the kidneys allowing the urine to flow freely. The problem arises when the ureters get inserted to form an angle at the junction. This results in restricted urinary flow.

• Kinking of the Ureters: When a blood vessel (arteries and veins) crosses the ureters abnormally, it can result in their twisting or kinking. The urine will not flow freely if the ureters are twisted.

If the condition is not present by birth, it can occur during the lifetime of an individual due to the following causes:

1. Retroperitoneal Fibrosis: It is a condition in which a mass of tissue forms in the space behind the stomach and intestine (retroperitoneal space). It forms because of the presence of excessive connective tissue. The tissue mass can obstruct the ureters inhibiting the flow of urine.

2. Retroperitoneal Lymphadenopathy: The small structures present throughout the body that support the immune system are lymph nodes. The lymph nodes present in the retroperitoneal space (behind the stomach and intestine) get enlarged in response to an infection known as retroperitoneal lymphadenopathy. The enlarged nodes obstruct the ureters restricting the flow of urine.

3. Ureteral Tumors: The uncontrolled growth of cells forms a mass known as a tumor which can turn cancerous later. The presence of tumors within the ureters can lead to ureteropelvic junction obstruction.

What Are the Symptoms of Ureteropelvic Junction Obstruction?

The condition can be diagnosed by ultrasound even before the symptoms appear. However, the following symptoms are present if the condition occurs late in life:

1. Presence of a lump or mass in the abdomen.

2. The urine does not get eliminated and remains within the body. Therefore, it increases the risk of urinary tract infections. Sometimes the infection is accompanied by fever.

3. The pain usually occurs in the back and the abdominal region when the person drinks water or any other fluid. It is because of the pressure on the kidneys due to the backflow of urine. The pain is usually periodic if the blockage is partial. Nausea and vomiting occur if the pain is severe.

4. Nephrolithiasis, or the presence of kidney stones, is usually seen because of the crystallization of salts present in the urine.

5. Hematuria or blood in the urine is usually seen due to a urinary tract infection.

How Does Ureteropelvic Junction Obstruction Cause Hydronephrosis?

The condition in which one or both the kidneys swell is known as hydronephrosis. Kidneys swell when the urine flows back to them due to the obstruction of the ureters. There is no specific age of occurrence of hydronephrosis as it can be diagnosed in babies by ultrasound or can be detected later in life. However, the causes of hydronephrosis are listed below:

• Ureteropelvic Junction Obstruction: The urine drains through the renal pelvis into the tubes known as ureters. This junction where the ureters meet the kidneys is known as the ureteropelvic junction. If the blockage occurs at this junction, the urine returns to the kidneys, causing them to swell, resulting in hydronephrosis.

• Vesicoureteral Reflux: The urine can flow back to the kidneys directly from the bladder through the ureters. This happens because of the obstruction of the bladder or urethra (the tube that drains urine outside the body).

How to Diagnose Ureteropelvic Junction Obstruction?

According to the international classification of diseases, 10th revision (ICD-10) authorized by the world health organization (WHO), the code for diagnosing ureteropelvic junction obstruction is N13.5. Therefore, the methods of diagnosis of ureteropelvic junction obstruction are listed below:

1. Blood Tests and Urine Sample: Blood reports, mainly the complete blood count, are essential for diagnosis because they provide an idea about the health of the kidneys and help detect the presence of infection. Urine samples, including the creatinine and blood urea nitrogen (BUN) tests, provide a check on the filtration mechanism of the kidneys. In case of infection, the rate of filtration of blood is reduced.

2. Ultrasound: It is an imaging test done to detect the obstruction even before the baby is born. Due to the blockage at the ureteropelvic junction, the kidneys swell. This condition is known as hydronephrosis and can be detected on ultrasound.

3. Intravenous Pyelogram: It is an imaging test in which a particular type of material is injected into the veins. As a result, X-ray images of the kidney, ureter, and urinary bladder are obtained, giving the doctor an idea if any blood is present in the urine or any other abnormality.

4. Nuclear Renal Scan: A special material is injected into the body through the veins. Images of the kidneys are obtained as the material flows into them with the help of a special camera to diagnose the condition and plan the treatment accordingly.

5. Retrograde Pyelography: An imaging test performed under general anesthesia to detect blockages present in the urinary system. A tube known as a catheter is inserted through the urethra up to the kidneys. The tube contains the dye (a special type of liquid) that flows upwards to the kidneys. X-ray images are obtained at various angulations to examine the kidneys and identify the blockage.

6. Magnetic Resonance Imaging (MRI) Technique: As the name suggests, this technique uses a combination of a magnetic field and radio waves to produce images of the internal organs of the body, so this test is of great use to get a clear picture of the kidneys.

7. Computed Tomography (CT Scans): In this test, X-ray images of the internal organs of the body are obtained. It also gives an idea about the presence of obstruction within the kidneys.

How Is a Ureteropelvic Junction Obstruction Treated?

If the baby is born with poor urinary drainage, it will improve over time and completely subside after eighteen months. However, treatment is required if the condition persists even after eighteen months. Surgical intervention can improve the flow of urine, and the surgical methods are listed below:

• Open Pyeloplasty: In this procedure, the doctor makes an incision below the ribs and removes the ureteropelvic junction. Ureters are then reattached to the kidneys (renal pelvis) to create a wide opening to facilitate the free flow of urine. The surgery aims to eliminate infection and relieve the symptoms. The patient stays in the hospital for two to three days.

• Laparoscopic Pyeloplasty: In this procedure, three small incisions are made in the abdomen through which the doctor or a robot inserts a telescope and surgical instruments. The procedure aims to repair the ureters that have become narrow or are obstructed. The advantage of the procedure is that it is minimally invasive, and the doctor need not place his hands in the abdomen. In addition, a tube known as a stent is left in place after the surgery to allow the drainage of urine.

• Internal Incision: A wire is inserted through the ureters to reach the ureteropelvic junction. The wire then cuts the narrow and obstructed junction internally. A drain is left in place for some days to facilitate urine drainage.

After the treatment, the recovery is quick. The patient might feel some pain and swelling in the ureters. The flow of urine also improves over time as healing progresses. A tube is usually left after the surgery to allow the urine to flow freely. The doctor will examine the kidneys through X-rays, and when the healing is complete, the kidneys might appear normal.

What Are the Complications of Ureteropelvic Junction Obstruction?

The complications of ureteropelvic junction obstruction are listed below:

1. Urinary tract infection repeatedly occurs because the urine is incompletely drained from the body. It becomes a source of infection if the condition is left untreated.

2. The patient feels pain in the back for a prolonged period causing discomfort, nausea, vomiting, and fever.

3. Chances of formation of kidney stones increase as the crystallization of salts occurs if the urine remains in the body for a long time.

4. Swelling (hydronephrosis) and permanent damage to the kidneys are seen if the blockage persists for a longer duration.

Conclusion:

The ureteropelvic junction is the point where the kidneys meet the ureters, and urine transfer occurs. If this junction is blocked, urine remains within the kidneys, causing them to swell. The condition presents with symptoms of pain and urinary tract infection early. The patient must consult the doctor as soon as any such symptoms are noted. Timely diagnosis and proper treatment will help the patient overcome the disease and save his kidneys from permanent damage. This, in turn, helps the patient to live a healthy life ahead.