Yo-Yo Renal Pelvis: An Unusual Cause of Flank Pain

Abstract

Herein we describe 2 patients in whom a bifid renal pelvis was associated with peristaltic dysfunction and pyelopelvic reflux, causing pyelocaliectasis and flank pain. The patients were improved with pyelopyelostomy. Previous explanations for the yo-yo phenomenon have indicated that there is functional obstruction because of a higher resting pressure in the common stem. The asynchronous peristaltic waves a coincident with a relatively low pressure in the oal fold that acted as a baffle to direct the flow of urine from the lower segment of the bifid pelvis down the ureter. This baffle favored reflux into the upper segment.

Yo-Yo Reflux in an Incomplete Duplex System Causing Severe Hydronephrosis in a Patient with Contralateral Renal Agenesis

“…[16] Once the diagnosis is established, therapy may ensue either as ureteropyelostomy [17] or pyelopyelostomy. [18] As demonstrated in this case, this measure may be decisive in preserving remaining renal function. …”

Scintigraphic detection of 'yo-yo' phenomenon in incomplete ureteric duplication

“…However, a disorder of peristalsis can occasionally occur at the site of ureteric fusion, causing urine to pass from one limb and reflux back into the other limb rather than down towards the bladder. This phenomenon had been described previously [4,5,6] and labelled as 'yo-yo' reflux or saddle reflux. Clinically, this can produce mild hydronephrosis and symptomatic loin pain.…”