Unique Variants of Megacalycosis on Magnetic Resonance Urography

To present a unique set of patients diagnosed with megacalycosis by magnetic resonance urography (MRU) to re-evaluate the definition of megacalycosis and provide a new perspective on diagnosis and treatment.

A retrospective chart review of patients with megacalycosis as diagnosed by MRU was conducted. MRU was performed to determine the presence of obstruction, further visualize renal anatomy, and clarify the presence of megacalycosis. Patients who were asymptomatic and demonstrated no evidence of obstruction were managed with long-term observation through renal bladder ultrasonography, and symptomatic patients who showed evidence of obstruction (crossing vessels, abnormal renal transit time, or disparity in differential renal function of <40%) were treated surgically with a dismembered Anderson-Hynes pyeloplasty.

Thirteen cases of megacalycosis were identified as diagnosed by MRU at our institution between 2007 and 2020. In 7 patients (54%), MRU revealed the simultaneous occurrence of obstruction and megacalycosis. In patients with obstruction (N = 7), surgical intervention was required to correct the obstruction via robotic pyeloplasty. In patients without obstruction (N = 6), conservative management was performed to monitor megacalycosis through long-term follow-up via routine ultrasounds.

While megacalycosis has historically referred to the non-obstructive dilatation of the renal calyces, our study presents 7 cases of obstruction occurring simultaneously with megacalycosis as diagnosed by MRU. By expanding the designation of megacalycosis to include patients with obstruction, surgical treatment can be explored to prevent future renal colic and/or renal deterioration in those patients.