Incomplete sealing of the urachus — a line of connectivity between a fetus and the umbilical cord — can cause a urachal cyst to develop. It can lead to abdominal pain and other symptoms and often affects older children and adults.

The urachus is a part of fetal development. It is a fibrous tube that extends from the upper aspect of a fetus’s bladder to the umbilicus and allows for urine removal.

During development, the urachus eventually seals, changing structure and closing off the portal between the naval and the bladder.

In some cases, a remnant of the original tube may remain and contribute to conditions known as urachal anomalies.

This article explains the symptoms, causes, and complications of a urachal cyst. It also outlines how doctors diagnose and treat the condition.

An infant with a urachal cyst.Share on Pinterest
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A urachal cyst occurs when a pocket forms in a remnant of the urachus, between the bladder and the naval. This fluid-filled sac can vary in size and clinical presentation.

Unlike some other urachal anomalies, a urachal cyst does not connect with the bladder or the naval. It forms in the middle of a urachal remnant after appropriate closure at the bladder and naval ends.

Many people live with urachal cysts unknowingly due to the absence of symptoms.

A urachal cyst is the most common type of urachal anomaly, and is thought to be rare.

It can develop at any age but is most common in older children and adults.

A urachal cyst may be small, uncomplicated, and asymptomatic. When symptoms present, there is often co-occurring infection or other complications.

Symptoms of a urachal cyst may include:

The symptoms of a urachal cyst can vary and may depend on the presence of other complications. Malignancy, severe infection, or other complications, like calculi deposits, can cause additional symptoms, such as:

Experts do not know the exact cause of urachal cysts and other urachal anomalies.

The urachus is present throughout gestation and possibly for a few days after birth. At this time, the urachus shrinks and changes from a tubular channel into a fibrous cord between the bladder and the naval.

Urachal anomalies occur when the urachus does not shrink and change, leaving remnant tissue that allows fluid to accumulate or leak.

The location of the remnant tissue determines which urachal condition someone may experience.

In addition to urachal cysts, three other types of urachal anomalies exist:

  • patent urachus
  • urachal sinus
  • urachal diverticulum

Urachal cysts may not cause discomfort or require medical attention. However, approximately 35% of people with these cysts present with painful symptoms that require treatment.

Infection is one possible complication of a urachal cyst. It occurs from the natural buildup of materials within the cyst and involves several bacterial populations, which can include Escherichia coli (E. coli).

Infected cysts may leak discharge into the abdominal cavity. In some cases, the cysts can rupture. They may drain into the bladder and mimic a urinary tract infection (UTI), cause painful skin discoloration, or result in an abdominal infection known as peritonitis.

Some urachal cysts may enlarge to the point of causing symptoms but never rupture.

If doctors do not completely remove a urachal cyst, cancer may develop. Urachal cancer is a type of bladder cancer. However, less than 1% of bladder cancers occur in the urachus.

The diagnosis of a urachal cyst involves a differential diagnosis to assess and rule out possible conditions.

An older article from 2006 states that urachal cyst symptoms can mimic those of other conditions, such as:

In addition to a physical exam, diagnostic imaging may help identify a urachal cyst and the presence of drainage or discharge into other areas of the body. Imaging tests may include:

Urachal cyst treatment will depend on the status of a cyst and any existing complications, such as rupture or peritonitis.

Treatment for cysts includes one or all of the following options:

  • antibiotics
  • drainage
  • surgical removal

The Urology Care Foundation (UCF) states that doctors should completely remove urachal remnants through surgery. The UCF does not consider draining urachal anomalies with a needle curative because it results in the recurrence of anomalies in approximately one-third of patients.

Surgery to remove a urachal cyst may be done:

Due to the potential for postsurgical infection, doctors often prescribe oral antibiotics before a cyst removal procedure.

If a person develops additional complications, they may need additional treatment.

Urachal cysts are not usually life threatening, and a full recovery is possible after treatment for infection or rupture.

In rare cases, a urachal cyst may lead to life threatening complications, such as urachal cancer or peritonitis.

Peritonitis is a medical emergency, and timely assessment is key to successful treatment.

Urachal cancer is an extremely rare complication of urachal cysts. When it occurs, it may extend into the bladder or other surrounding structures, possibly spreading to other areas of the body.

Due to the rarity of urachal cancer, its outlook depends on each person. There are currently no standardized treatment protocols.

A urachal cyst is a sac-like formation in the abdomen resulting from a congenital anomaly involving the urachus.

When the urachus does not complete its natural structural change, it can allow a fluid pocket to build up in the space between the bladder and the naval.

Many urachal cysts are asymptomatic, but infection or other complications can cause symptoms to present.

Antibiotic therapy, drainage, and surgery may be necessary to completely treat a urachal cyst. In rare instances, abdominal infection or the presence of cancer may pose serious health concerns.