Female, 64 years old, with right lateral thigh pain status post L4-5 TLIF and PSF. Findings are seen compatible with posterior instrumented fusion from L4 to L5. Also noted is right-sided laminotomy for placement of interbody bone graft at L4-5. Within the laminotomy defect, there is a fluid collection measuring 27 x 23 x 23 mm which is T2 hyperintense and T1 hypointense. This collection appears to extend slightly into the discectomy defect. This collection encroaches upon the spinal canal causing effacement of the right aspect of the thecal sac and the right L4-5 neural foramen. The soft tissues surrounding this collection are not particularly edematous or inflamed.Spinal alignment is anatomic on this examination. Vertebral body height and morphology are within normal limits. Apart from mild degenerative endplate signal changes at L4 and L5, and a Schmorl's node superiorly at L2, no significant marrow signal abnormality or edema is detected.As above, there is a moderate narrowing of the spinal canal at L4-5 with moderate narrowing of the right neural foramen. Elsewhere, no significant spinal canal or neuroforaminal compromise is seen.
Findings are redemonstrated compatible with posterior instrumented fusion and interbody fusion at L4-5.Within the right L4-5 laminotomy defect, a fluid collection has developed causing encroachment on the spinal canal and neural foramen. This collection is favored to represent a seroma, with pure hematoma and CSF pseudomeningocele considered less likely possibilities. Lack of surrounding inflammation would argue against an infected collection.