Duplicated ureter or duplex collecting system is a congenital condition in which the

ureteric bud The ureteric bud, also known as the metanephric diverticulum, is a protrusion from the mesonephric duct during the development of the urinary and reproductive organs. It later develops into a conduit for urine drainage from the kidneys, which, in c ...

, the embryological origin of the

ureter The ureters are tubes composed of smooth muscle that transport urine from the kidneys to the urinary bladder. In an adult human, the ureters typically measure 20 to 30 centimeters in length and about 3 to 4 millimeters in diameter. They are lin ...

, splits (or arises twice), resulting in two ureters draining a single

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

. It is the most common renal abnormality, occurring in approximately 1% of the population.Siomou E. et al
Duplex collecting system diagnosed during the first 6 years of life after a first urinary tract infection: a study of 63 children
Journal of Urology, 2006; 175(2):678-81; discussion 681-2J. Gatti, J. Murphy, J. Williams, H. Koo, emedicine overview
Ureteral Duplication, Ureteral Ectopia, and Ureterocele
/ref>

Pathophysiology

Ureteral development begins in the human fetus around the 4th week of

embryonic development In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermat ...

. A ureteric bud, arising from the mesonephric (or Wolffian) duct, gives rise to the ureter, as well as other parts of the collective system. In the case of a duplicated ureter, the ureteric bud either splits or arises twice. In most cases, the kidney is divided into two parts, an upper and lower lobe, with some overlap due to intermingling of collecting tubules. However, in some cases the division is so complete as to give rise to two separate parts, each with its own

renal pelvis The renal pelvis or pelvis of the kidney is the funnel-like dilated part of the ureter in the kidney. It is formed by the convergence of the major calyces, acting as a funnel for urine flowing from the major calyces to the ureter. It has a mucous ...

and ureter.

Diagnosis

Prenatally diagnosed

hydronephrosis Hydronephrosis is the hydrostatic dilation of the renal pelvis and Renal calyx, calyces as a result of obstruction to urine flow downstream. Alternatively, hydroureter describes the dilation of the ureter, and hydronephroureter describes the dila ...

(fluid-filled kidneys) suggest post-natal follow-up examination. The strongest neo-natal presentation is

urinary tract infection A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower urinary tract infections may involve the bladder (cystitis) or urethra (urethritis) while upper urinary tract infections affect the kidney (pyel ...

. A hydronephrotic kidney may present as a palpable abdominal mass in the newborn, and may suggest an ectopic ureter or ureterocele. In older children, ureteral duplication may present as: * Urinary tract infection – most commonly due to

vesicoureteral reflux Vesicoureteral reflux (VUR), also known as vesicoureteric reflux, is a condition in which urine flows retrograde, or backward, from the urinary bladder, bladder into one or both ureters and then to the renal calyx or kidneys. Urine normally trave ...

(flow of urine from the bladder into the ureter, rather than vice versa). *

Urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a significant effect on quality of life. Urinary incontinence is common in older women ...

in females occurs in cases of ectopic ureter entering the vagina, urethra or vestibule.

Classification

Ureteral duplication is either of: ; Partial: I.e., the two ureters drain into the

bladder The bladder () is a hollow organ in humans and other vertebrates that stores urine from the kidneys. In placental mammals, urine enters the bladder via the ureters and exits via the urethra during urination. In humans, the bladder is a distens ...

via a single common ureter. Partial, or incomplete, ureteral duplication is rarely clinically significant. ; Complete: In which the two ureters drain separately. Complete ureteral duplication may result in one ureter opening normally into the bladder, and the other being ectopic, ending in the

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

, the

urethra The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated ...

or the

vulval vestibule The vulval vestibule (also known as the vulvar vestibule or vestibule of vagina) is the part of the vulva between the labia minora. At the innermost part are the vaginal introitus and urinary meatus. The Bartholin's and Skene's glands each ha ...

. These cases occur when the ureteric bud arises twice (rather than splitting).Sadler, T. W., Langman's medical embryology - 11th ed. p. 240, .

Prevalence

Duplicated ureter is the most common renal abnormality, occurring in approximately 1% of the population. It occurs in about 0.7% of healthy adults and in 2% to 4% of people with urinary tract issues. Reviewed: 12/04/2020 ; Race: Duplicated ureter is more common in

White Americans White Americans (sometimes also called Caucasian Americans) are Americans who identify as white people. In a more official sense, the United States Census Bureau, which collects demographic data on Americans, defines "white" as " person hav ...

than in

African-Americans African Americans, also known as Black Americans and formerly also called Afro-Americans, are an American racial and ethnic group that consists of Americans who have total or partial ancestry from any of the Black racial groups of Africa. ...

. ; Sex: Duplicated ureter is more common in females. However, this may be due to the higher frequency of

s in females, leading to a higher rate of diagnosis of duplicated ureter.

Complications

A duplicated ureter increased the risk of: *

Hydronephrosis Hydronephrosis is the hydrostatic dilation of the renal pelvis and Renal calyx, calyces as a result of obstruction to urine flow downstream. Alternatively, hydroureter describes the dilation of the ureter, and hydronephroureter describes the dila ...

Urinary tract infection A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower urinary tract infections may involve the bladder (cystitis) or urethra (urethritis) while upper urinary tract infections affect the kidney (pyel ...

(UTI) *

Vesicoureteral reflux Vesicoureteral reflux (VUR), also known as vesicoureteric reflux, is a condition in which urine flows retrograde, or backward, from the urinary bladder, bladder into one or both ureters and then to the renal calyx or kidneys. Urine normally trave ...

* Incontinence

References