A urachal remnant is a leftover piece of a tube-like structure that was supposed to close before birth but didn’t fully disappear. This tube, called the urachus, originally connected the bladder to the belly button during fetal development. In most people it degrades into a thin, fibrous cord with no function. When it fails to close completely, the remaining tissue is called a urachal remnant, and it sits in the midline of the abdomen between the top of the bladder and the navel. About 0.063% of adults have one, and most never know it until imaging picks it up or it becomes infected.
How the Urachus Develops and What Goes Wrong
During fetal life, the urachus serves as a channel between the developing bladder and the umbilical cord. By the time a baby is born, this channel normally collapses and transforms into the median umbilical ligament, a small band of tissue buried in the abdominal wall that serves no active purpose. When that collapse is incomplete, some portion of the original tube persists as a hollow or partially open structure. The leftover tissue can take several forms depending on which section stayed open and which closed off.
The Four Types of Urachal Remnants
Urachal remnants are classified into four categories based on which part of the tube remains open:
- Patent urachus (about 50% of cases): The entire tube stays open from the bladder to the belly button. This creates a direct channel that can leak urine from the navel. It is usually diagnosed in newborns, but milder forms occasionally escape detection until adulthood.
- Urachal cyst (about 30%): The tube closes at both ends but stays open in the middle, forming a fluid-filled pocket. Because it is sealed off, it tends to sit silently until it becomes infected or is found incidentally on a scan.
- Urachal sinus (about 15%): The tube closes at the bladder end but stays open at the belly button end, forming a blind pouch that drains toward the navel. It often shows up as recurring periumbilical inflammation or discharge.
- Vesicourachal diverticulum (about 5%): The tube closes at the belly button end but stays open where it meets the bladder, creating a small outpouching from the bladder dome. Up to 50% of these contain calcifications visible on imaging.
What It Feels Like When Symptoms Appear
Most urachal remnants in adults produce no symptoms at all. They are frequently discovered by accident during a CT scan or ultrasound ordered for something else. When they do cause trouble, infection is almost always the trigger.
The hallmark symptom of an infected urachal remnant is purulent (pus-like) discharge from the belly button, often paired with redness, tenderness, and lower abdominal pain centered around the navel. One reported case described the pain as a 7 out of 10. Fever and a palpable midline mass below the navel can also develop. A patent urachus may leak clear or urine-like fluid from the belly button even without infection.
Because these symptoms are uncommon, they are frequently misdiagnosed as superficial skin infections, umbilical dermatitis, or simple abscesses, particularly in people with obesity or diabetes. A useful clinical clue: lower midline abdominal pain combined with belly button discharge should raise suspicion for a urachal problem, while pain alone without discharge is more likely caused by conditions like appendicitis or a urinary tract infection.
How It Is Diagnosed
Ultrasound is typically the first imaging test. It can show a fluid-filled or tube-shaped structure sitting in the midline above the bladder that should not be there. A urachal cyst appears as a small pocket of fluid that does not connect to the navel. A sinus looks like a narrow tube running toward the belly button. A patent urachus shows a continuous channel between bladder and navel.
CT scans with contrast provide more detail and are better at revealing complications like infection, abscess formation, or calcification. MRI adds further information when there is concern about malignancy, because it can characterize the tissue inside the remnant more precisely. For a patent urachus, a voiding cystourethrogram (an X-ray taken while the bladder is emptying) can confirm that contrast dye travels from the bladder up through the open channel.
One important limitation: imaging alone is not reliable at distinguishing a benign urachal remnant from a malignant one. One study found that CT had a specificity of only 21% and a negative predictive value of just 43% for identifying cancer. When there is any concern about malignancy, cystoscopy (a camera placed into the bladder) and tissue biopsy are needed to confirm the diagnosis.
When and How Urachal Remnants Are Treated
There is no firm consensus on managing an asymptomatic urachal remnant found by accident. Some experts recommend surgical removal because of the theoretical link between chronic inflammation and malignant transformation. Others take a watch-and-wait approach, noting that these anomalies almost never require intervention and that prophylactic treatment for cancer prevention is not generally advocated. The decision often comes down to the size and type of the remnant, the patient’s symptoms, and the surgeon’s judgment.
When a remnant becomes infected, the traditional approach is a two-stage procedure. First, the abscess or infected cyst is drained and antibiotics are given to clear the infection. After a waiting period of roughly 5 to 14 days (averaging about 12 to 13 days), the remnant is surgically removed along with a small cuff of bladder tissue where the urachus was attached. Some surgeons perform a single-stage excision, removing the infected remnant and bladder cuff in one operation, though this is more commonly done when infection is minimal.
Laparoscopic (keyhole) surgery is the standard approach for removal. Hospital stays in studies of complicated cases have averaged around two weeks, with patients who need bladder cuff removal tending to stay longer and requiring a urinary catheter for an average of about 11 days. Long-term outcomes are excellent. Follow-up studies extending nearly four years have shown no symptom recurrence or voiding difficulties after surgery.
The Cancer Connection
The most serious complication of a urachal remnant is malignant transformation, most often into urachal adenocarcinoma. This is extremely rare, with an estimated incidence of about 1 in 5 million people per year. It accounts for only 0.01% of all adult cancers and 0.34 to 0.7% of all bladder cancers.
The most common warning sign is blood in the urine. Research has found a 17-fold increase in the likelihood of malignancy when hematuria is present alongside a known urachal remnant. Because these tumors are so uncommon, they are often diagnosed at advanced stages. Five-year survival rates range from roughly 38% to 49% depending on the center and stage at diagnosis, with some evidence suggesting that treatment at specialized centers leads to better outcomes.
For people living with a known urachal remnant, the practical takeaway is that cancer risk is vanishingly small but not zero. New blood in the urine, unexplained belly button discharge, or a growing midline mass warrants prompt evaluation.