Isolated pelvic fluid in males on outpatient magnetic resonance imaging examinations: Differences in incidence based on age

Purpose: Determine the incidence and amount of isolated pelvic fluid in males, stratified by age, on outpatient pelvic magnetic resonance imaging (MRI) examinations performed for lower back or extremity pain.

Methods: After institutional review board approval, 161 pelvic MRIs performed on males for musculoskeletal or neurologic indications over an 18-month period were retrospectively reviewed for isolated pelvic fluid by 2 radiologists. Patients with a potential etiology for the fluid were excluded. Volume and maximal 2-dimensional measurements of fluid were calculated. Statistical analysis included logistic regression,Wilcoxon ranksum, and w2 tests.

Results: Twenty (44.4%) of 45 patients 5 to 29 years old, 5 (10%) of 50 patients 30 to 49 years old, and 4 (6.1%) of 66 patients older than 50 years had isolated pelvic fluid (P < 0.001). Mean volume of fluid was 2.5 mL; 97% (28/29) had less than 10 mL. Mean maximal 2-dimensional measurement was 2.1 cm2; 93% (27/29) had less than 6 cm2.

Conclusions: Isolated fluid is greater than 7 times more common on outpatient pelvic MRIs in males younger than 30 years compared with men older than 49 years. Fluid rarely exceeded 10 mL or 6 cm².