🚑 Ureteropelvic Junction Obstruction and Hydronephrosis

The ureteropelvic junction (UPJ) is the point where the renal pelvis transitions into the ureter, allowing urine to flow from the kidney to the bladder. When this junction becomes narrowed or obstructed, urine cannot drain properly, leading to a condition known as hydronephrosis.

🔍 What Is Ureteropelvic Junction Obstruction?

Ureteropelvic junction obstruction occurs when urine flow is partially or completely blocked at the junction between the kidney and the ureter. This obstruction causes urine to back up into the kidney, resulting in progressive dilation of the renal pelvis and calyces.

UPJ obstruction may be:

• Congenital (most common, due to abnormal muscle development or crossing vessels)

• Acquired (from kidney stones, scarring, infection, or trauma)

💧 How Does Hydronephrosis Develop?

When urine cannot pass efficiently through the UPJ:

1. Urine accumulates in the renal pelvis

2. The pelvis and calyces become dilated

3. Persistent pressure damages renal tissue

4. Kidney function may decline over time

In the infographic:

• The left image shows normal anatomy with proper urine drainage.

• The right image demonstrates obstruction at the UPJ, leading to marked dilation and hydronephrosis.

📊 Ureteropelvic Junction Obstruction vs Normal Anatomy

Feature	Normal Ureteropelvic Junction	UPJ Obstruction with Hydronephrosis
Urine flow	Free flow from renal pelvis to ureter	Partially or completely obstructed
Renal pelvis	Normal size	Dilated
Calyces	Normal shape	Dilated and blunted
Kidney pressure	Normal intrarenal pressure	Increased pressure within kidney
Renal parenchyma	Preserved	Progressive thinning with chronic obstruction
Symptoms	Usually asymptomatic	Flank pain, UTIs, hematuria, nausea
Risk to kidney function	None	Risk of progressive renal damage
Management	No treatment needed	Observation or surgical correction

⚠️ Clinical Features

Symptoms vary with age and severity:

• Infants: Antenatal hydronephrosis on ultrasound

• Children: Abdominal mass, urinary tract infections

• Adults: Flank pain, nausea, hematuria, recurrent UTIs

Chronic obstruction can lead to irreversible renal damage if untreated.

🧪 Diagnosis

UPJ obstruction is diagnosed using:

• Ultrasound (detects hydronephrosis)

• CT urography

• Diuretic renography (assesses drainage and renal function)

🛠️ Management

Treatment depends on severity:

• Observation for mild, asymptomatic cases

• Surgical correction (pyeloplasty) for significant obstruction

• Endoscopic or minimally invasive approaches in select patients

Early intervention helps preserve kidney function and prevent complications.

✅ Key Takeaway

Ureteropelvic junction obstruction is a common cause of hydronephrosis, especially in children. Recognizing the anatomical blockage and understanding its effect on urine flow is essential for timely diagnosis and management.

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