Leiomyoma of the urinary bladder is a rare benign tumour predominantly found in women, although men can also be affected. The most common presenting complaints are urinary voiding symptoms such as obstruction and irritation.
It exhibits characteristics similar to those of uterine leiomyomas on ultrasound, CT and MRI. Usually characterised as a smooth-walled homogeneous solid mass within the bladder wall.
It is the most common benign neoplasm but accounts for only 0.4 % of all bladder tumours. Leiomyomas occur equally in men and women with a broad age range of 22-78 years 1. Approximately 75% of the patients are young and middle aged 2.
Most are small and asymptomatic and are discovered incidentally. However, large tumours manifest with symptoms such as 1:
- hesitancy, frequency, dribbling
- pressure from mass effect
- urinary obstruction
It is a non-infiltrative smooth muscle tumour lacking mitotic activity, cellular atypia, and necrosis 1. Leiomyomas arise in the submucosa, but growth may be submucosal (7%), intravesical (63%), or extravesical (30%). At cystoscopy, normal bladder mucosa covers the leiomyoma.
Imaging features include either a smooth indentation of the bladder wall or an intraluminal mass. The lesions are smooth, solid, homogeneous masses. Cystic components indicate degeneration. The tumour exhibits characteristics similar to those of their uterine counterpart at US, CT, and MR imaging, with MR imaging being most accurate for tissue characterization 1.
- US examination typically shows a smooth-walled homogeneous hypoechoic solid mass in the bladder with thin echogenic surface 3
- with US it is possible to determine the endovesical, intramural or extravesical nature of the lesion 3
- reveal smooth-walled solid lesion with homogeneous echogenicity
- CT is accurate in detection and localisation of these lesions, by presenting it as hypodense mass 3
- contrast-enhanced CT scan the lesion is shown as a moderately enhancing mass 2
MRI is superior in demonstrating the submucosal origin of the tumour and the preservation of the muscle layer. The imaging characteristics are similar to uterine leiomyomas:
- intermediate signal intensity
- low signal intensity
- degenerated leiomyomas have more heterogeneous signal characteristics; cystic areas have high signal intensity
T1 C+ (Gd):
- contrast enhancement is variable; degenerated areas lack enhancement
Treatment and prognosis
Focal excision of the mass is the treatment of choice. A preoperative suspicion of a leiomyoma is invaluable in alerting the surgeon to the benign nature of the mass and preventing unnecessary radical surgery 1.
A pedunculated intraluminal leiomyoma may be confused with a urothelial lesion or transitional cell carcinoma of the bladder but should be of lower signal intensity on T2-weighted images 1.
- 1. Wong-you-cheong JJ, Woodward PJ, Manning MA et-al. From the Archives of the AFIP: neoplasms of the urinary bladder: radiologic-pathologic correlation. Radiographics. 26 (2): 553-80. doi:10.1148/rg.262055172 - Pubmed citation
- 2. Sudhakar PJ, Malik N, Malik A. Leiomyoma of bladder. Saudi J Kidney Dis Transpl. 2008;19 (2): 232-5. Saudi J Kidney Dis Transpl (full text) - Pubmed citation
- 3. Yung-Wei Lin, Thomas I-Sheng Hwang. Leiomyoma of Urinary Bladder: A Case Report and Literature Review. J Urol Roc Vol.12 No.2, June 2001 PDF (full text)