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Review literature: (Shokeir and Nijman, 2000) (Mouriquand and Wilcox, 1998).
Definition of Megaureter
A megaureter is an anomaly with a dilated ureter of more than 7–8 mm, the further division is made according to the cause:
Primary Obstructive Megaureter:
The primary obstructive megaureter is caused by a prevesical aperistaltic ureter segment, which causes a dilatation of the prestenotic ureter. The stenosis is caused by an embryological stop of the ureter development.
Secondary Obstructive Megaureter:
Increased intravesical pressure, increased bladder wall tension and scarring lead to the decompensation of the uretero-vesical junction, e.g. megaureter due to neurogenic bladder dysfunction or posterior urethral valves.
Vesicoureteral reflux causes dilatation of the ureter (primary refluxing megaureter). Secondary refluxing megaureter is caused by bladder outlet obstruction.
Idiopathic (not obstructive or refluxing) Megaureter:
Most newborn megaureter are idiopathic megaureter, the cause often remains unclear. Increased urine production, a delay of ureteral maturation or subclinical obstruction may contribute to the development of a megaureter.
Refluxing and Obstructive Megaureter:
The megaureter is caused by the combination of the distal stenosis and vesicoureteral reflux (rare).
Epidemiology of Megaureter
Megaureter account for 20% of cases with prenatally diagnosed hydronephrosis.
Diagnosis of Megaureter
Ultrasonography may differentiate between ureteropelvic junction obstruction and megaureter. The ureter in children is usually less than 5 mm wide.
Urography is also well suited for the differential diagnosis between uretero-pelvic junction obstruction and megaureter. Furthermore, imaging provides information about the kidney function.
Urography of bilateral primary obstructive megaureter. With kind permission of Prof. Dr. R. Harzmann, Augsburg.
Voiding cystourethrogram is used for the confirmation or exclusion of vesicoureteral reflux and to detects posterior urethral valves.
Renal scintigraphy is used to determine renal function (Glomerular filtration rate). In combination with a diuretic, renal scintigraphy can distinguish between real obstruction and idiopathic (non-obstructive) megaureter. The wash-out after 20 minutes of furosemide injection should be more than 50%.
Retrograde pyelography is used for imaging, if the anatomy or differential diagnosis is unclear with above mentioned techniques [fig. primary obstructive megaureter].
|Primary obstructive megaureter: as seen with retrograde pyelography. With kind permission of Dr. R. Gumpinger, Kempten.|
Whitaker's Perfusion Test:
With the help of a percutaneous nephrostomy, the renal pelvic pressure is determined during a flow rate of 10 ml/min. Whitaker test is indicated if renal scintigraphy is unclear, especially in poor kidney function.
Treatment of Megaureter
Treatment of Obstructive Megaureter:
Indications for surgery are a significant obstruction as demonstrated with renal szintigraphy and progressive loss of kidney function. The primary obstructive megaureter in children has a good spontaneous resolution rate without surgery.
Surgical technique: excision of the narrow ureteral segment, ureter modellage (folding or vessel-sparing longitudinal resection) and ureteroneocystostomy.
Treatment of Secondary Obstructive Megaureter:
Treatment of the underlying disease should be sufficient.
Please see section vesicoureteral reflux, in most cases medical management is sufficient. If surgery is necessary, ureteroneocystostomy after ureter modellage is the technique of choice.
Observation and conservative treatment (of e.g. infections) is sufficient.
|Diseases of the ureters||Index||Retrocaval ureter|
Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- Shokeir und Nijman 2000 SHOKEIR, A. A. ; NIJMAN, R. J.:
- Primary megaureter: current trends in diagnosis and treatment.
In: BJU Int
86 (2000), Nr. 7, S. 861–8
- Wilcox und Mouriquand 1998 WILCOX, D. ; MOURIQUAND, P.:
- Management of megaureter in children.
In: Eur Urol
34 (1998), Nr. 1, S. 73–8
Deutsche Version: Megaureter