Pelvic lipomatosis - Detection, mandatory documentation and follow-up

Clinical History

51-year-old lady of African-Caribbean background, presented with complaints of pelvic pain. An ultrasound was performed, which showed a suspicious large pelvic collection. She was referred for a MRI for further imaging.

Imaging Findings

Axial T1w and T2w (Fig. 1c, b), coronal T1w (Fig. 1a, d) and sagittal T2w images (Fig. 1e) show a band of circumferential lobulated tissue surrounding the rectosigmoid colon. The band of tissue shows signal drop out, suggestive of adipose tissue (Fig. 1f). No invasion into perivesical or parametrial tissues are noted. Multiple sigmoid diverticuli are noted.

Discussion

Pelvic lipomatosis represents excessive deposition of fat in the pelvis due to overgrowth of adipose cells particularly in the perivesical and perirectal regions, leading to compression of pelvic organs. Pelvic lipomatosis is more frequently seen in people of African origin [3].

The clinical presentation depends on the level of compression. If it compresses the pelvic vasculature, pedal oedema is seen. If it compresses the rectum/sigmoid then tenesmus and ribbon-shaped stools are seen. If it compresses the urinary bladder then dysuria and hydronephrosis may manifest [1, 3].

In patients with severe obstructive lipomatosis, intravenous pyelogram will show a pear-shaped urinary bladder with dilated ureters [6]. CT findings show areas of symmetric fat density in the pelvic region. On MRI, the fatty area will show T1 and T2 hyperintensity, with signal drop out on the fat suppressive sequence like STIR. In this patient, a band of fatty tissue is seen surrounding the sigmoid colon.

It is important to recognise pelvic lipomatosis as it is linked to obesity, Cushing's disease, diabetes and frequent urinary tract infections [4, 5]. However, the exact aetiology has not yet been established.
Differential diagnosis includes malignant lesion like liposarcoma (mixed with solid enhancing components), pelvic haematomas, abscess and lymphadenopathy.

A conservative approach, the use of symptomatic treatment and follow-up, is indicated in cases with minor symptoms [5]. It is impossible to predict which patients will experience deteriorating renal function, hence follow-up is mandatory to prevent diversion surgeries for urinary tract obstructions [1]. One study has revealed that 40% of patients progress to urinary diversion surgeries in 5 years [7]. A yearly ultrasound appointment to look for obstruction with correlated renal function test is recommended [5]. Patients with abnormal ultrasound or renal functions tests can have MRI imaging to see the extent of progression and especially if they are of the Afro-Carribbean race.

Differential Diagnosis List

Final Diagnosis

Pelvic lipomatosis with non-obstructive features

URL:	https://eurorad.org/case/12084
DOI:	10.1594/EURORAD/CASE.12084
ISSN:	1563-4086