From the Guidelines
A kidney with a double moiety refers to a kidney that has two separate collecting systems, each with its own ureter, renal pelvis, and calyces, which is a variation of renal anatomy that may be mistaken for pathologic conditions. This condition is also known as a duplex kidney or duplicated collecting system. It occurs during embryonic development when two ureteric buds form from the mesonephric duct instead of the normal single bud. The upper moiety typically drains the upper pole of the kidney, while the lower moiety drains the lower pole. Some key points to consider about double moiety kidneys include:
- They are present in approximately 1% of the population and are more common in females
- They may be asymptomatic and discovered incidentally, but they can also be associated with complications such as ureterocele, vesicoureteral reflux, or urinary tract infections
- The upper moiety ureter often inserts more medially and inferiorly into the bladder (Weigert-Meyer rule), which can predispose to obstruction, as discussed in the emergency ultrasound imaging criteria compendium by the American College of Emergency Physicians 1. Management of double moiety kidneys depends on whether complications are present and may range from observation to surgical intervention if there are recurrent infections or significant obstruction. Key considerations in the management of double moiety kidneys include:
- Monitoring for signs of complications such as urinary tract infections or obstruction
- Imaging studies such as ultrasound or CT scans to evaluate the anatomy and function of the kidney
- Surgical intervention if necessary to correct any obstructive lesions or other complications, as would be identified using emergency ultrasound imaging criteria 1.
From the Research
Definition of Double Moiety (Renal Moiety)
A kidney with a double moiety, also known as a duplex kidney, refers to a congenital anomaly where a single kidney has two separate collecting systems, each with its own ureter [ 2, 3, 4 ]. This condition can be asymptomatic, but it can also lead to complications such as hydronephrosis, vesicoureteral reflux, and ureterocele [ 2 ].
Characteristics of a Duplex Kidney
A duplex kidney can have various characteristics, including:
- Two ureters arising from a single kidney [ 2 ]
- A duplicated renal collecting system [ 3 ]
- An obstructed or poorly functioning upper or lower pole renal moiety [ 5, 6 ]
- Hydronephrosis or hydroureteronephrosis in one or both moieties [ 2, 4 ]
Clinical Implications
The presence of a duplex kidney can lead to various clinical implications, including: