Adenocarcinoma of the urinary bladder is rare and accounts for only ~1% of all bladder cancers (90% are transitional cell carcinomas).

Pathology

Metaplasia of urinary bladder induced by chronic irritation or infection can lead to adenocarcinoma. Pathological types of adenocarcinoma of the urinary bladder are:

1. mucinous adenocarcinoma
2. signet-ring type
3. papillary adenocarcinoma
4. not otherwise specified (NOS)

Bladder adenocarcinoma may be subclassified as primary (two-thirds are non-urachal and one-third are urachal ²) or secondary (metastases).

Aetiology

• persistent urachal remnant (most common)
• cystitis glandularis (itself secondary to bladder outlet obstruction, chronic infection and/or bladder calculi)
• schistosomiasis (bilharziasis), especially where endemic
• associated with bladder exstrophy

Radiographic features

CT

Non-urachal adenocarcinoma

• diffuse bladder wall thickening
• stranding of perivesical fat
• regional lymphadenopathy
• invasion of rectus muscles

Urachal adenocarcinoma

• characteristically in the midline at the dome of the bladder, or along the course of urachus (from the bladder to umbilicus)
  • a midline, infraumbilical soft tissue mass with peripheral calcification is characteristically urachal adenocarcinoma unless proven otherwise (calcification in 70% of cases)
• usually large tumours (5-6 cm) with prominent extravesical component
• mixed solid-cystic appearance in most cases

MRI

Solid components of the tumour are isointense, while cystic mucinous component appears hyperintense on T2W images. Localising a urachal carcinoma may be easier on the sagittal images.

Treatment and prognosis

Due to their extravesical location, urachal carcinomas present very late and thus carry a poor prognosis. Radical cystectomy is considered the treatment of choice. However, en bloc resection of the extravesical component, adjacent peritoneum and the abdominal wall is also needed.