Duplicated ureter is a congenital condition

Congenital disorder

A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 in which the ureteric bud

Ureteric bud

The ureteric bud is a protrusion from the mesonephric duct during the development of the urinary and reproductive organs. It later develops into the adult kidney, except for the nephrons, which, in contrast, originate from the metanephric blastema....

, the embryological origin of the ureter

Ureter

In human anatomy, the ureters are muscular tubes that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually long and ~3-4 mm in diameter....

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

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

. It is the most common renal abnormality, occurring in approximately 1% of the population . The additional ureter may result in a ureterocele

Ureterocele

A ureterocele is a congenital abnormality found in the urinary bladder. In this condition called ureteroceles, the distal ureter balloons at its opening into the bladder, forming a sac-like pouch. It is most often associated with a duplicated collection system, where two ureters drain their...

, or an ectopic ureter

Ectopic ureter

Ectopic ureter is a medical condition where the ureter, rather than terminating at the urinary bladder, terminates at a different site. In males this site is usually the urethra, in females this is usually the urethra or vagina...

.

Pathophysiology

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

Human embryogenesis

Human embryology is the study of human development during the first eight weeks from gametogenesis pre-conception through fertilization up to and including the 8th week after implantation of the zygote in the uterus...

. A ureteric bud, arising from the mesonephric (or Wolffian) duct

Wolffian duct

The mesonephric duct is a paired organ found in mammals including humans during embryogenesis....

, 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

Renal pelvis

The renal pelvis or pyelum is the funnel-like dilated proximal part of the ureter in the kidney.In humans, the renal pelvis is the point of convergence of two or three major calyces...

 and ureter.

Classification

Ureteral duplication is either:

• Partial - i.e. the two ureters drain into the bladder
  Urinary bladder
  The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
  
   via a single common ureter. Partial, or incomplete, ureteral duplication is rarely clinically significant.

or

• 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
  Ectopic ureter
  Ectopic ureter is a medical condition where the ureter, rather than terminating at the urinary bladder, terminates at a different site. In males this site is usually the urethra, in females this is usually the urethra or vagina...
  
  , ending in the vagina
  Vagina
  The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
  
  , the urethra
  Urethra
  In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
  
   or the vulval vestibule
  Vulval vestibule
  The Vulval vestibule is a part of the vulva between the labia minora into which the urethral opening and the vaginal opening open...
  
  . These cases occur when the ureteric bud arises twice (rather than splitting).

Prevalence

Duplicated ureter is the most common renal abnormality, occurring in approximately 1% of the population .
Race: Duplicated ureter is more common in Caucasians than in African-Americans.
Sex: Duplicated ureter is more common in females. However, this may be due to the higher frequency of urinary tract infection

Urinary tract infection

A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...

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

Clinical Presentation

Prenatally diagnosed hydronephrosis

Hydronephrosis

Hydronephrosis is distension and dilation of the renal pelvis calyces, usually caused by obstruction of the free flow of urine from the kidney, leading to progressive atrophy of the kidney...

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

Urinary tract infection

A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...

. 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
  Vesicoureteral reflux is an abnormal movement of urine from the bladder into ureters or kidneys. Urine normally travels from the kidneys via the ureters to the bladder...
  
   (flow of urine from the bladder into the ureter, rather than vice versa).
• Urinary incontinence
  Urinary incontinence
  Urinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...
  
   in females occurs in cases of ectopic ureter entering the vagina, urethra or vestibule.

See also

• Ureterocele
  Ureterocele
  A ureterocele is a congenital abnormality found in the urinary bladder. In this condition called ureteroceles, the distal ureter balloons at its opening into the bladder, forming a sac-like pouch. It is most often associated with a duplicated collection system, where two ureters drain their...
  
  
• Ectopic ureter
  Ectopic ureter
  Ectopic ureter is a medical condition where the ureter, rather than terminating at the urinary bladder, terminates at a different site. In males this site is usually the urethra, in females this is usually the urethra or vagina...
  
  
• Kidney development
  Kidney development
  Kidney development, or nephrogenesis, describes the embryologic origins of the kidney, a major organ in the urinary system. It is often considered in the broader context of the development of the urinary and reproductive organs.-Phases:...