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Megacalycosis

Definition:

Megacalycosis is a rare, congenital, nonobstructive dilatation of the renal calyces with a normal renal pelvis and ureter and without vesicoureteral reflux.

Epidemiology:

Very rare, usually unilateral, and more common in men than in women.

Pathophysiology:

Underdevelopment of the renal medulla results in short collecting ducts and an increased number of calyces. Megacalycosis causes a mild impairment of maximal urinary concentrating capacity; the long-term prognosis for kidney function is good.

Signs and symptoms:

Patients are usually asymptomatic.

Diagnostic Workup of Megacalycosis

Megacalycosis is usually detected incidentally on imaging. It is essential to differentiate it from obstructive hydronephrosis or ureteropelvic junction obstruction.

Sonography:

Dilatation of the collecting system is limited to the renal calyces.

CT or MR urography:

The imaging modality of choice for the differential diagnosis of urinary tract ectasia. Typical findings are nonobstructive calyceal dilatation with a normal renal pelvis and ureter.

Intravenous urography:

Intravenous urography shows enlarged calyces and an increased number of calyces. The renal pelvis is not dilated, and the ureter is slender [fig. Megacalycosis in intravenous urography].

VCUG:

No vesicoureteral reflux in voiding cystourethrography; the examination is particularly useful in unclear cases or in children.

Renal scintigraphy:

Renal scintigraphy shows normal kidney function with prompt radionuclide washout.

Megacalycosis: Intravenous urography shows enlarged calyces and an increased number of calyces. The renal pelvis is not dilated, and the ureter is slender. With kind permission, Dr. G. Antes, Kempten.

Treatment of Megacalycosis

Specific treatment is unnecessary.

  Deutsche Version: Megakalikose

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