Urachus cyst as a congenital anomaly

Among the cysts - pathological formations in the form of closed cavities with various contents - there is such a deviation in embryonic structures as a cyst of the urachus, which occurs during intrauterine development. According to ICD-10, this is a congenital anomaly of the urinary duct, code - Q64.4

Epidemiology

Pathologies associated with unreduced urachus residue, according to some data, affect just over 1% of the population, and cysts account for up to 30% of cases (while completely open urachus accounts for almost 48% of cases of its anomaly).

Most often (in 40% of cases) the urachus cyst occurs in children of the first two years of life (approximately one case per 5 thousand newborns); more than 30% of these cystic formations are diagnosed in children aged two to six years and almost 24% in children over seven years old. [1]

Experts point out that urachus anomalies in adults rarely manifest themselves and are discovered by chance. Moreover, compared with women, urachus cyst in men is detected one and a half to two times more often. [2]

Causes urachus cysts

Like the omphalomesenteric (intestinal yolk) duct, the fetal urinary duct, the urachus, which drains the bladder and connects it to the umbilical cord, is a temporary extraembryonic (provisional) organ. As the  human embryo develops,  such organs or structures usually regress or undergo natural obliteration (infection). [3]

The causes of the anomalies of the urachus, including the formation of its cysts, lie in the incomplete overgrowth of this embryonic structure, that is, they are associated with its incomplete involution, which leads to various pathologies.

Thus, the urachus cyst, localized in the navel (below the navel or above the bladder), refers to dysontogenetic cystic formations. [4]

Risk factors

Today, general risk factors for the development of congenital cysts are considered to be genetically determined features of embryogenesis, as well as certain disorders of the cellular and intercellular metabolism of the mesenchyme in the perinatal period, which cause pathological changes in the tissues of various anatomical structures of the fetus. [5]

The following factors are considered as probable factors that increase the risks of intrauterine anomalies: pathologies of pregnancy, in particular, later with maturation of the placenta ; teratogenic effects of the environment; alcohol and  smoking during pregnancy  , etc.

Pathogenesis

The mechanism of formation - the pathogenesis of the urachus cyst - is explained by violations of the timing of the formation and subsequent anatomical transformation of extraembryonic structures of the fetus, the rate of formation of the abdominal wall and prolapse of the bladder.

So, urachus is the remnant of allantois, which is formed from the endoderm and extraembryonic mesenchyme around the third week of pregnancy. In the first weeks of intrauterine development, it is associated with the embryo, providing the processes of gas exchange and excretion of metabolic products into the amnion (amnionic bladder).

Reduction of allantois with its further transformation into a tubular duct extending from the anterior wall of the bladder - urachus - is noted between the fifth and seventh weeks of embryonic development. Moreover, in the first three months of pregnancy, since the bladder is just beginning to form (from the seventh week of gestation), this duct is open and functions like allantois. [6]

However, at the beginning of the second trimester of pregnancy, when the fetal bladder begins to descend into the pelvic cavity, the urachus stretches, and by the sixth month of intrauterine development, the lumen in it disappears with the formation of the median umbilical ligament (median umbilical ligament) between the peritoneum and the transverse fascia of the anterior abdominal wall.

In cases where the middle part of the rudimentary tubular structure (between the navel and the bladder) does not overgrow, a closed cavity is formed in the remaining lumen, lined with a transitional epithelium - a urachus cyst, the walls of which consist of muscle fibers, and inside there may be liquid and exfoliated epithelium. [7]

Symptoms urachus cysts

Urachus abnormalities - unless inflammation occurs - are often asymptomatic.

For many, the first signs may appear when it is bacterially infected with cysts of Staphylococcus, E. Coli, Pseudomonas or Streptococcus. [8]

In infants, the size of the cystic formation present in the umbilical region can increase tenfold, and this causes symptoms such as more frequent urination, flatulence, discomfort in the retroperitoneal space, which are manifested by anxiety and crying of the child. And in newborns with such an anomaly, the umbilical cord becomes wet and does not heal for a long time.

Read also -  Cyst in a child: main types, localization, causes and symptoms

With a significant size of the cyst in adults, it manifests itself as a constant feeling of fullness in the abdominal cavity and overcrowding of the bladder, problems with bowel function arise. During pregnancy, a urachus cyst can manifest itself in women who complain of pulling pains below the navel, aggravated by movement.

Cysts can open through a fistula in the navel, and their contents can also come out as a  discharge from the navel .

With an inflamed cyst, abdominal pains appear below the navel (especially severe during bowel movements) and fever; the area near the navel turns red and may swell; possible pain during urination and / or hematuria (blood in the urine). [9]

A suppurating cyst of the urachus can rupture - with the release of purulent exudate through the navel or getting it inside the bladder or abdominal cavity. In the first case, pyuria is observed, and in the second there is a threat of  peritonitis .

Complications and consequences

Infection of the cyst and its inflammation are fraught with serious consequences and complications, in particular, its suppuration, which was mentioned above, as well as the formation of an umbilical fistula.

The result of a prolonged outflow of purulent exudate can be  omphalitis of the navel .

A long-term complication of cysts is malignancy, the incidence of which, according to clinical data, does not exceed 0.01%.

Diagnostics urachus cysts

Diagnosis begins with examination and palpation of the abdominal wall. Blood and urine tests may also be prescribed to check for a bacterial infection.

Instrumental diagnostics of cystic formation of the urachus is carried out using imaging methods: sonography (ultrasound) of the abdominal cavity and suprapubic region of the abdomen (bladder), computed tomography (CT), magnetic resonance imaging (MRI). Cystography is also performed.

The urachus cyst is visualized on ultrasound in the form of an extra-abdominal mass with low echogenicity, located between the skin and the anterior abdominal wall, below the navel - along the midline of the abdomen. The contents of an inflamed cyst may appear patchy.

Differential diagnosis

Differential diagnosis is carried out with a cyst of the mesentery or vitelline duct, hernia - the umbilical or anterior abdominal wall, with a diverticulum of the bladder or ileum (Meckel's diverticulum), with inflammation of the pelvic organs.

Treatment urachus cysts

As a rule, the presence of an asymptomatic urachus cyst does not need medical intervention. It's another matter if it increases or is accompanied by some symptoms. And the third situation is when the cyst becomes inflamed. And in the last two cases, treatment is necessary. [10]

And this is a surgical treatment, which consists in draining and  removing the cyst  (for small sizes - laparoscopically). [11], [12]

Prevention

To date, it is impossible to prevent a congenital anomaly of the fetal urinary duct.

Forecast

The long-term prognosis for a urachus cyst - unless it becomes infected - is considered favorable.