Urachal Cyst
A urachal cyst is a fluid-filled sac that forms along the urachus, a tubular structure that connected the developing bladder to the umbilical cord (belly button) in the fetus and normally closes off and becomes a fibrous cord (called the median umbilical ligament) before birth. When part of the urachus fails to close completely, a small portion may persist as a cyst, typically located between the top of the bladder and the umbilicus. Most urachal cysts are small and cause no symptoms, and many are identified incidentally on imaging done for other reasons. Some become infected, cause abdominal or umbilical symptoms, or, rarely, develop malignant transformation. Evaluation typically combines imaging (ultrasound, CT, or MRI), clinical assessment, and, in selected cases, cystoscopy or biopsy.
What is it?
During fetal development, the urachus is a tubular structure that connects the top (dome) of the developing bladder to the umbilical cord. It carries fluid between the fetal bladder and the placenta during a specific phase of development. Before birth, the urachus normally closes off and shrinks down to become a fibrous cord called the median umbilical ligament, which runs from the top of the bladder to the umbilicus (belly button) in the midline of the lower abdomen. When part of the urachus fails to close completely, various types of urachal remnants can persist into childhood or adulthood.
There are four main types of urachal remnants, and understanding them helps clarify what a urachal cyst is.
A patent urachus is a complete failure of the urachus to close, with an open channel between the bladder and the umbilicus. This is typically identified in infancy because of leakage of urine from the umbilicus.
A urachal sinus is an outward-opening remnant, in which the umbilical end of the urachus remains connected to the surface but the bladder end has closed. This may present with drainage from the umbilicus.
A vesicourachal diverticulum is an inward-opening remnant, in which the bladder end remains open (creating a small pouch at the dome of the bladder) but the umbilical end has closed. This may cause urinary stasis at the diverticulum and, in some patients, recurrent infections.
A urachal cyst is a closed fluid collection anywhere along the urachal remnant, with both the bladder and umbilical ends of the involved segment closed off. Urachal cysts are the most common type of urachal remnant identified in adults, and their location—typically in the midline between the top of the bladder and the umbilicus, within the space behind the abdominal wall muscles and in front of the peritoneum (the space of Retzius or preperitoneal space)—is characteristic.
Most urachal cysts are small (often 1 to a few centimeters in size) and cause no symptoms. Many are identified incidentally on ultrasound, CT, or MRI performed for unrelated reasons. Because the bladder dome sits behind the pubic bone and the urachal remnant runs upward from there toward the umbilicus, urachal cysts can occur anywhere in this midline path. Their appearance on imaging is typically that of a well-defined, thin-walled fluid collection.
When symptoms occur, they most often relate to infection. A urachal cyst can become infected (typically with bacteria that reach it through nearby structures or hematogenously), leading to a urachal cyst abscess. Symptoms then include lower abdominal or umbilical pain, redness, swelling, and tenderness in the midline lower abdomen or around the umbilicus, discharge from the umbilicus (which may be purulent), fever, and general symptoms of infection. Infected urachal cysts can occasionally rupture into surrounding tissues or, less commonly, into the bladder or umbilicus. Recurrent infections are also possible.
Less commonly, urachal cysts can present with other symptoms such as a palpable mass in the lower abdomen or, in rare cases, symptoms related to pressure on nearby structures. In children, urachal remnants may be identified in the setting of persistent umbilical discharge or recurrent umbilical infections.
Malignant transformation of urachal remnants into urachal cancer is rare but well recognized. Urachal cancer typically arises from a urachal remnant at the dome of the bladder and is most commonly an adenocarcinoma (arising from glandular cells that can develop in urachal remnants), though other types can occur. Urachal cancer accounts for a small proportion of all bladder cancers overall. It often presents with blood in the urine, mucus in the urine (particularly with adenocarcinomas), a palpable mass, or, in some cases, umbilical discharge. Any concerning features of a urachal remnant on imaging—such as a solid mass, thickened irregular walls, calcifications, unusual enhancement patterns, or growth over time—warrant careful evaluation for possible malignancy.
Diagnosis is based on imaging. Ultrasound is often the first-line imaging test and can identify urachal cysts as fluid collections in the characteristic midline location. CT with and without contrast provides detailed anatomical information and can help distinguish urachal remnants from other conditions such as bladder diverticula, hernias, or intra-abdominal cysts. MRI can also be useful and is an option for patients in whom radiation should be minimized or when detailed soft tissue characterization is needed. The diagnosis of a urachal cyst is typically straightforward when the imaging appearance and location are characteristic.
When infection is suspected, blood tests including complete blood count, inflammatory markers, and, if applicable, blood cultures may be obtained. Urinalysis and urine culture help assess for associated urinary tract infection. Additional testing is guided by the clinical context.
Cystoscopy may be used in selected patients, particularly when malignancy is suspected or to evaluate the bladder for related findings. Biopsy is reserved for cases where malignancy is a concern, typically obtained either during surgical management or with image-guided approaches.
Important to Know
Management of urachal cysts depends on the patient’s age, symptoms, imaging findings, and any complications. Care is typically coordinated by primary care clinicians, urologists (or pediatric urologists in children), general surgeons, and, when needed, radiologists, infectious disease specialists, or oncologists.
For infants and children with urachal remnants, care is generally coordinated by pediatric urologists or pediatric general surgeons. Many small, asymptomatic urachal remnants in young children may resolve on their own, and observation is often reasonable. Surgical treatment is considered for symptomatic remnants, persistent or recurrent problems, or specific anatomical situations.
For adults, management of urachal cysts has become increasingly individualized based on the imaging appearance and clinical context.
For small, asymptomatic urachal cysts with a typical benign appearance identified incidentally in adults, observation without surgery is often appropriate. Reassurance about the benign nature of the finding is often the primary management, and no ongoing surveillance imaging is required in the absence of clinical concerns. This represents a shift from earlier practice, in which surgical removal of urachal remnants was often recommended primarily because of the concern for future malignancy. However, given that the lifetime risk of urachal cancer in an incidentally identified small benign-appearing urachal cyst appears to be low, current thinking increasingly favors observation for typical asymptomatic cases.
For urachal cysts with concerning features on imaging—such as a solid component, thickened irregular walls, calcifications, unusual enhancement patterns, larger size, or growth over time—more thorough evaluation is appropriate. This may include additional imaging, cystoscopy, and, when needed, biopsy or surgical excision for definitive diagnosis and treatment.
For infected urachal cysts, treatment typically includes antibiotics directed at the likely and identified organisms, and, in many cases, drainage of the infected collection. Drainage may be performed percutaneously (through the skin, under image guidance) or surgically depending on the specific circumstances. Once the acute infection is controlled, surgical removal of the urachal remnant is often recommended to prevent recurrence, particularly in patients who have had recurrent infections.
For symptomatic urachal cysts with recurrent problems, or for those requiring surgical treatment for other reasons, complete surgical excision of the urachal remnant is typically recommended. The standard surgical approach involves removing the entire urachal remnant from the umbilicus to the bladder dome, along with a small cuff of the bladder at the connection point (partial cystectomy). This can be performed using open, laparoscopic, or robotic-assisted techniques depending on the specific situation, the surgeon’s expertise, and other factors. Complete excision is important because leaving any portion of the urachal remnant behind can result in recurrence or, potentially, malignant transformation.
For confirmed urachal cancer, treatment follows established principles and typically involves partial cystectomy with removal of the entire urachal remnant and the umbilicus (en bloc resection), often with lymph node dissection. Because urachal cancers are frequently adenocarcinomas, treatment principles differ somewhat from typical urothelial bladder cancers, and systemic therapy (when needed) may involve different regimens. Care is best delivered in centers with experience in this rare cancer, and multidisciplinary teams that include urologic oncology, medical oncology, radiation oncology, and pathology are important.
Care during pregnancy in patients with urachal remnants is typically straightforward, though awareness of the anatomical variation is important, particularly if surgery or procedures involving the lower abdomen may be needed. Coordination with obstetrics is helpful.
For patients with a history of urachal remnant surgery or who have been diagnosed with urachal cancer, long-term follow-up is important. The specifics depend on the diagnosis and treatment.
Care is typically coordinated by urologists and, when needed, general surgeons and other specialists. Imaging and clinical findings are interpreted alongside the patient’s symptoms, examination, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding the anatomical variation, the meaning of the specific imaging findings, the rationale for recommended monitoring or treatment, warning signs of complications, and, when relevant, the specific plans for follow-up all contribute to appropriate care. For asymptomatic incidental urachal cysts, clear reassurance about the generally benign nature of the finding and the low likelihood of complications is often important.
Red flag symptoms include severe lower abdominal or umbilical pain, high fever with chills, redness and swelling spreading from the umbilicus or lower abdomen (which may indicate spreading infection or cellulitis), significant purulent drainage from the umbilicus, symptoms of sepsis (severe illness, low blood pressure, rapid heart rate, confusion), significant blood in the urine, symptoms of urinary tract infection with fever, a palpable enlarging mass in the lower abdomen or umbilical area, unintended weight loss, or rapid clinical deterioration. These warrant prompt or urgent medical evaluation, as they may indicate infection, abscess, malignancy, or other serious complications.