Presentation
Hematuria. History of renal stones.
Patient Data
There a round, enhancing mass in the anterior dome of the bladder, which appears associated with the urachus. On the non-contrast images, a small non-obstructive calyceal stone is incidentally noted in the right kidney.
It is quite easy to overlook this subtle finding on axial images, but much more obvious on sagittal reformats. This patient likely had an urachal diverticulum and not a fully patent urachus, as the remainder of the obliterated urachus looks normal on sagittal images. It is essential to look at the bladder in all three planes when working up hematuria, as subtle mass may only be well appreciated in a single plane.
Finally, it is worth noting that the mass is also visible on the non-contrast images. Often when using narrow window/level settings, a subtle (or not-so-subtle) bladder mass may be visible on a more commonly performed non-contrast "renal stone protocol" CT when a patient is being worked up for hematuria, potentially diagnosing the disease at an even earlier time. Careful evaluation of the bladder is essential, even on non-contrast CT's, particularly in higher-risk patients.
Case Discussion
Primary adenocarcinoma of the bladder is rare. Although it is most classically associated with bladder exstrophy and patent urachus, two-thirds of cases are non-urachal (favoring the bladder base) and only one-third urachal. Risk factors include chronic mucosal irritation and urinary diversions. Patients can present with hematuria, irritative symptoms, mucus in the urine, or umbilical discharge.
Most cases of urachal adenocarcinoma occur near the bladder, with the remainder along the course of the urachus. These are distinguished by the prominent extravesicular components of the mass and often contain calcifications. They are typically large at presentation (mean 6 cm), high grade, and have diffusely invaded the bladder wall at diagnosis. Extravesicular spread and metastases are common.
Due to the location, urachal adenocarcinoma usually presents late and has a poor prognosis. Aggressive surgical excision is often performed including the posterior rectus fascia, peritoneum, and abdominal wall. In this case of pathology-proven adenocarcinoma, the patient was treated with partial cystectomy instead of more aggressive surgery, due to the small size and lack of invasion of adjacent structures.
Squamous cell and urothelial carcinoma can also occur in the urachus, but less frequently than adenocarcinoma. Metastatic adenocarcinoma to the bladder is more common than primary disease, and typically a late manifestation of cancer.
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