The urachus is an embryonic remnant connecting the fetal bladder to the allantois, which becomes the umbilical ligament in adults. Malclosure can result in cell proliferation and malignancy, specifically urachal carcinoma (UrC), a rare cancer that comprises <1% of all bladder cancers. Typically presenting between ages 50–60, UrC is highly aggressive with a poor prognosis; the 5-year overall survival is around 50%, and cancer-specific survival is approximately 35%.

We report a case of a 39-year-old female with a history of asthma and severe left acute pyelonephritis-induced kidney atrophy, who presented to our emergency room with fever, severe abdominal pain, gross hematuria for 3 months, watery diarrhea, and anuria. Physical examination showed abdominal tenderness with rebounding pain. Lab results indicated leukocytosis, elevated CRP, and significant proteinuria. Imaging studies revealed an 11.6 cm mass along the urachus with massive ascites. The patient underwent exploratory laparotomy, partial cystectomy, and umbilical resection, revealing a ruptured mucinous urachal cystadenocarcinoma, classified as Sheldon stage IIIC.

Urachal cancer is rare, occurring in 0.2% of bladder neoplasms, often asymptomatic in early stages. Symptoms like hematuria (80%) and mucinuria (15%) typically appear late, with most diagnoses made after tumor extension to the bladder wall. Early and complete surgical intervention, including lymphadenectomy, is critical for improving survival rates.

Physicians should be vigilant for symptoms like hematuria, suprapubic pain, and bladder wall thickening on imaging. Timely treatment and surveillance can significantly enhance patient outcomes.