53-year-old male with sepsis and history of osteomyelitis with a rectal exam concerning for sacral osteomyelitis. The coccyx is absent, presumably related to prior resection. There is ulceration of the soft tissues posterior to the distal sacrum to the left of midline which courses distally along the gluteal crease toward the perineum. There is a thin collection of rim-enhancing fluid along the ulceration which contains gas and may communicate with the skin surface. The inflammation abuts the fifth sacral segment and extends anterior to the S5 segment and also into the spinal canal to the level of S2/S3 as well as along the right S2 and S3 nerve roots. The S5 segment shows low signal intensity on T1-weighted images, increased signal intensity on T2-weighted images, and enhances after contrast administration compatible with the suspected history of osteomyelitis. There is relatively mild signal abnormality and enhancement within the S4 segment that could reflect osteomyelitis or simply reactive edema. The bone marrow signal intensity of the remainder of the sacrum appears normal, as does the signal intensity of the remainder of the bones of the pelvis. Note is made of multiple sinus tracts within the perineum compatible with the patient's history of perineal fistulas related to the patient's known history of Crohn's disease. There is also a linear focus of T2 signal abnormality extending to the bladder concerning for fistula formation. Again seen are postoperative changes of proctectomy with a right lower quadrant colostomy, appearing similar to the prior study. A Foley catheter is in place. A pigtail catheter is identified within the bladder. There is gas density within the pelvis, particularly along the right iliopsoas muscle, better seen on the patient's recent CT examination. There is an ovoid collection of high signal intensity on both T1 and T2-weighted images, posterior to the psoas muscle at the level of the lumbosacral transition, which may represent a small hematoma. There is edema within the subcutaneous fat of the right flank which is nonspecific. Overall the subcutaneous edema has improved when compared to the prior study. There is mild intramuscular edema within the right proximal hip musculature that does not enhance following contrast administration. There is mild nonspecific and nonenhancing edema of the abductor musculature of the left hip. A small amount of fluid is identified within both hips, within normal limits.
1. Soft tissue ulceration as described above with inflammation extending along the anterior aspect of the lower sacrum as well as into the sacral spinal canal. Signal abnormality and enhancement of the S5 segment is compatible with osteomyelitis with possible osteomyelitis of the S4 segment as well.2. Gas density within the pelvis is better seen on the patient's recent abdomen/pelvis CT examination. Please see the discussion above for additional details.