Osteomyelitis pubis with entero-articular fistula

Case contributed by Joshua Yap

Presentation

Right groin pain for 1 month. Previous cystectomy and ileal conduit formation.

Patient Data

Age: 85 years
Gender: Male

Pelvic Xray

x_ray

Pelvic xray demonstrates cortical destruction of the pubic symphysis with focal osteopenia suggestive of osteomyelitis. Contrast is present within the ileal conduit from a recent CT study. A left hip prosthesis, aortoiliac stent and pelvic surgical clips are in situ.

CT abdomen and pelvis

ct

CT demonstrates gas within and adjacent to the pubic symphysis concerning for infection. There is no discrete collection however the right adductor muscles are thickened and ill-defined. A previous cystectomy with ileal conduit formation is noted. A right iliac endoleak (Type 2) and moderate hiatus hernia are also demonstrated.

MRI pelvis - 1 week later

mri

MRI performed 1 week later demonstrates symmetrical and diffuse marrow edema involving the pubic symphysis and bilateral superior pubic rami. There is associated patchy loss of fatty marrow signal and avid contrast enhancement of the pubic symphysis. There is also a small amount of fluid within the pubic symphysis with inferolateral extension into the right adductor longus muscle where it forms a 9.3 x 3.2 cm multiloculated collection consistent with an abscess. Some extension into the left adductor longus muscle is also demonstrated. There is minimal subchondral irregularity within the pubic symphysis.

There is surrounding global inflammatory change involving the pelvic floor muscles with a small amount of pelvic free fluid.

Appearances are in keeping with septic arthritis and osteomyelitis of the pubic symphysis with an associated intramuscular abscess on a background of a diffuse inflammatory process consistent with radiation change.

Pubic symphysis arthrogram

Fluoroscopy

The adductor longus abscess was aspirated and grew polymicrobial bowel flora. A pubic symphysis arthrogram was therefore performed to assess for an enteric fistula.

An 18G needle was inserted into the pubic symphysis under ultrasound and fluoroscopic guidance and water-soluble contrast injected. Contrast filled a loop of ileum posterior to the pubic symphysis via a narrow tract extending superiorly from the joint. Contrast also filled the right adductor collection.

A fistula between the pubic symphysis and ileum was confirmed.

Case Discussion

Osteomyelitis pubis is a rare condition and can be difficult to distinguish from osteitis pubis, a non-infectious inflammatory process. Though rarer still, a secondary entero-articular fistula should be considered when intra-articular and intra-muscular gas is present without an overlying soft tissue defect. This was further supported by cultures positive for bowel flora. The fistula was occult on oral contrast CT and could only be confirmed via a fluoroscopically-guided arthrogram.

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