A urachal diverticulum (also ''vesicourachal diverticulum'') is a

congenital disorder A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

caused by the partial persistence of the

allantois The allantois ( ; : allantoides or allantoises) is one of the extraembryonic membranes arising from the yolk sac. It is a hollow sac-like structure filled with clear fluid that forms part of the developing conceptus in an amniote that helps the ...

. The allantois, which later becomes the

urachus The urachus forms from the distal end of the allantois in the embryo, and develops into a closed cord between the base of the bladder, and the navel. It drains the bladder of the fetus that joins and runs within the umbilical cord. The fibrous r ...

, connects an embryo's

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 ...

to the

yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...

. Normally, the urachus closes off to become the

median umbilical ligament In human anatomy, the median umbilical ligament is an unpaired midline ligamentous structure upon the lower inner surface of the anterior abdominal wall. It is covered by the median umbilical fold. The median umbilical ligament represents the re ...

; however, if it does not seal close to the bladder, a blind pouch connected to the bladder remains. This is usually asymptomatic but can lead to recurrent

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 ...

s. If the urachus is wholly patent,

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

can drain from the bladder to an opening by the umbilicus, a condition known as

urachal fistula A urachal fistula is a congenital disorder caused by the persistence of the allantois (later, urachus), the structure that connects an embryo's bladder to the yolk sac. Normally, the urachus closes off to become the median umbilical ligament; howev ...

References

Congenital disorders of urinary system {{Genitourinary-disease-stub}