Malignant Supravesical Mass in Urachal Remnant

Case History: A 20-year-old female was admitted with a two-month history of abdominal pain, constipation, weight loss, and discharging sinus tract with history of appendicectomy with pelvic abscess 9 months prior. Biopsy showed adenocarcinoma.

Further ultrasonography and contrast CT scan abdomen with per rectal positive contrast were performed.

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Figure 1. A, Ultrasonography with curvilinear probe showing heterogeneously hypoechoic mass lesion (arrowhead) with internal air foci (star) and posterior infiltration into sigmoid colon (arrow).

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Figure 1. B, Ultrasonography with linear probe showing same finding with linear sinus tract (star) formation in the anterior abdominal wall.

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Figure 2. A, Plain Axial CT scan showing heterogeneously hypodense lesion in pelvic cavity. Linear tract of positive rectal contrast with few air foci.

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Figure 2. B, Plain Axial CT scan showing superficial extension of lesion with sinus tract formation.

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Figure 3. Contrast Enhanced Axial CT scan showing heterogeneous enhancement with posterior sigmoid colon involvement.

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Figure 4. Contrast enhanced sagittal CT scan showing heterogeneous enhancement of supravesicle lesion with two sinus tract formations in anterior abdominal wall, inferior lesion involves dome of urinary bladder (solid arrow) with air foci in bladder and sigmoid colon extension posterior.

CECT Abdomen Findings
There is an ill-defined heterogenously enhancing soft tissue density mass lesion in the pelvis infraumbilical (supravesical) region in midline with few internal, nonenhancing, hypodense necrotic areas and little air foci within.

• Superiorly, it extends up to the umbilical region and shows loss of fat plane with small bowel loops.
• Inferiorly, it infiltrates into the dome of urinary bladder. There are air foci within the urinary bladder.
• Anteriorly, it shows infiltration of both rectus abdominis muscles.
• Posteriorly, it lies in close relation with the uterus, however, fat plane appears preserved.
• On plain scan, contrast filled linear hyperdense tract of approximately 2.5 cm with 2 mm diameter, it is tracking posteriorly and communicating with sigmoid colon.
• There is infiltration into the sigmoid colon in the form of segment circumferential asymmetric wall thickening.
• There are three linear tracts along the anterior abdominal wall and are noted as communicating to the above mentioned lesion and appear to extend up to the skin and subcutaneous tissue.

Discussion

• The urachus is an embryologic remnant of the fetal genitourinary tract seen as a tubular structure extending in the midline between the dome of the bladder and the umbilicus that usually involutes before birth and remains in adults as the median umbilical ligament.

Various Pathology Involving Urachal Remnant

• Congenital Urachal Anomalies: There are four types of congenital urachal anomalies:
• Patent urachus (most common)
• Umbilical-urachal sinus
• Vesicourachal diverticulum
• Urachal cyst

Acquired Urachal Remnant Diseases

• Infection: Urachal tract remnants that abnormally remain patent are often subject to infection. Furthermore, these infected remnants are frequently confused with a wide spectrum of midline intraabdominal or pelvic in?ammatory disorders at clinical examination and with malignant tumors at imaging.
• Tumors
• Benign urachal neoplasms: adenomas, fibromas, fibroadenomas, fibromyomas, and hamartomas are extremely rare.
• Malignant urachal neoplasm are also rare, representing less than 0.5% of all bladder cancers.

Although the normal urachus is most commonly lined by the transitional epithelium, urachal carcinoma predominantly manifests as adenocarcinoma (90% of cases). It is believed to arise from malignant transformation of columnar or glandular metaplastic epithelium, and mucin production is found in up to 75% of cases on histological analysis.

These tumors can be silent because of their extra peritoneal location, and, consequently, usually present at an advanced stage, and often show local invasion or metastases to the pelvic lymph nodes, lung, brain, liver, or bone. Hematuria, dysuria, abdominal pain, and umbilical discharge are the most common symptoms.

The diagnostic evaluation for urachal carcinoma should include a careful history and physical examination. A urine analysis with cytology may be helpful. Although carcinoma of the urachus can occur in any site along the urachal tract, the most common locations are the dome of the bladder and the umbilicus.

US may demonstrate a supravesical complex cystic mass. CT or MR confirm the US ?ndings and provide more information about local extent of the disease, pelvic lymph-node involvement, and systemic metastases. On CT, urachalcarcinoma is usually seen as a midline mass anterosuperior to the dome of the bladder that can be solid, cystic, or mixed. In 60% of cases, low-attenuation components are seen, representing mucin content. Like other mucinous adenocarcinomas, urachal carcinomas may produce calci?cations, which may occur in 50%-70% of cases, and are considered nearly pathognomonic for urachal adenocarcinoma. On MR imaging, a mass with increased signal intensity is usually seen on T2-weighted images because of the presence of mucin within the tumor.

The radiologic differential diagnoses include benign urachal tumors that may mimic malignancy, like adenomas, fibromas, fibromyomas, and hamartomas, infected urachal remnants, and other malignant tumors like adenocarcinomas of nonurachal origin, transitional cell carcinomas, and metastases originating from primary lesions of the colon, prostate, or female genital tract .

Primary treatment of localized disease includes wide local excision of the urachus, umbilicus, and surrounding soft tissue combined with partial or radical cystectomy and bilateral pelvic lymphadenectomy. A cystoscopy is necessary to evaluate whether the carcinoma has penetrated the urothelium of the bladder and a transurethral biopsy should be performed, if possible.

References
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5. Mengiardi B, Wiesner W, Stoffel F, et al. Case 44: adenocarcinoma of the urachus. Radiology. 2002;222:744-747.
6. Henly DR, Farrow GM, Zincke H. Urachal cancer: role of conservative surgery. Urology. 1993;42:635-639.