Ultrasound diagnostics of megaureter
During pelvic ultrasound (US), the key finding is visualization of a dilated ureter. Dilation can be traced down to the level of the vesicoureteric junction (vesicoureteric junction).
A crucial step in ultrasound is to exclude signs of distal obstruction. The radiologist must ensure that the dilation is not caused by:
- Calculi (stones) in the distal sections;
- Ureterocele (cystic dilation of the intravesical segment of the ureter).
Functional and radioisotope methods
To clarify the diagnosis and assess the functional state of the urinary system, additional methods are used:
- Micturition cystography (micturating cystogram). The study is performed to assess urine backflow. In true non-refluxing megaureter, vesicoureteral reflux is not detected.
- Radioisotope renography with MAG3. The resulting images (scintigrams) clearly show a pronounced dilation of the affected ureter (e.g., left) along its entire length—from the renal pelvis to the vesicoureteric junction.
This comprehensive approach allows for confident differentiation of megaureter from other pathologies (such as hydronephrosis or nephroptosis).
Autosomal recessive polycystic kidney disease (ARPKD)
As part of the differential diagnosis of retroperitoneal masses, autosomal recessive polycystic kidney disease (Autosomal Recessive Polycystic Kidney Disease - ARPKD) should be considered.
The imaging findings of ARPKD include:
- Plain abdominal radiography: displacement of intestinal loops into the mid-abdomen (mid-abdomen) is observed. This is due to large mass lesions (significantly enlarged kidneys) in the retroperitoneal space.
- Renal ultrasound (standard mode): pronounced bilateral renal enlargement (nephromegaly) and increased echogenicity of the renal parenchyma are detected.
- High-resolution ultrasound: multiple microcysts (microcysts) are clearly visualized within the parenchyma.
Briefly: answers to topical questions
What diagnostic imaging methods are used for the comprehensive evaluation of patients with megaureter?
A number of diagnostic imaging methods are used for the comprehensive evaluation of patients with megaureter.
- Ultrasonography (US) — assesses the presence of ureterocele, signs of reflux, bilateral involvement, and peristalsis.
- Micturating cystourethrography (MCUG / VCUG) or contrast-enhanced voiding urosonography (ce-VUS) — performed to confirm or rule out vesicoureteral reflux.
- Magnetic resonance urography (MRU) — used in complex anatomical situations to assess peristalsis, drainage, and renal function.
- Radioisotope renography (with MAG3 and diuretic challenge) — used to confirm obstruction and determine the disease subtype.
What clinical and radiological classifications and types of megaureter exist?
Congenital megaureter (Congenital Megaureter) is classified into four main types depending on the presence of reflux and obstruction.
- Refluxing, non-obstructed (refluxing, non-obstructed) — type with reflux and no obstruction.
- Refluxing, obstructed (refluxing, obstructed) — type with a combination of reflux and obstruction.
- Non-refluxing, non-obstructed (non-refluxing, non-obstructed) — type without reflux and obstruction.
- Non-refluxing, obstructed (non-refluxing, obstructed) — type with obstruction and no reflux.
Additionally, based on the causes of dilation, primary megaureter, refluxing megaureter, non-refluxing non-obstructive hydroureter, and secondary hydroureter (associated with posterior urethral valves or ureterocele) are distinguished.
The diagnostic algorithm for megaureter is the rule of three "U"s: Ultrasound (looking for dilation down to the segment), Ureterocele and stones (ruling out obstruction), Urethrocystography (ruling out reflux).
What else to study on this topic
- Technique of pelvic ultrasound for visualizing the distal ureters
- Radioisotope renography with MAG3: principle of the method and curve interpretation
- Differential diagnosis of hydronephrosis and megaureter
- High-resolution ultrasound in the evaluation of microcysts in polycystic kidney disease
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