Case Author(s): J. Philip Moyers, MD , 10/2/95 . Rating: #D2, #Q4

Diagnosis: Soft tissue abscess involving left superior and inferior pubic ramus

Brief history:

Decreased ambulation on the left lower extremity.


Anterior flow images of the pelvis

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View second image(bs). Anterior delayed images of the pelvis

View third image(xr). Anterior plaim film of the pelvis

View fourth image(mr). Axial MR images and intraoperative ultrasound image of the same area

Full history/Diagnosis is available below

Diagnosis: Soft tissue abscess involving left superior and inferior pubic ramus

Full history:

Patient had prior documented E coli urinary tract infection four weeks before this study. The patient currently presents with a 1-3 week history of decreased ambulation of the left lower extremity. The patient currently has an increased white cell count and a moderately increased sedimentation rate. Plain film of the pelvis suggests an obstruction in the inferior pubic ramus medial to the ischial pubis synchondrosis. The patient was referred for three-phase bone scintigraphy to evaluate for osteomyelitis.


5.1 mCi Tc-99m MDP i.v.


The anterior radionuclide angiogram demonstrates increased flow in the region of the left groin. Immediate static images also demonstrate increased activity in the left superior and inferior pubic region. The combination of findings of increased flow and a destructive lesion in the left inferior pubic ramus prompted an MRI of the pelvis, which demonstrates abnormal tissue which enhances in the left obturator internus. At this time, soft tissue infection with involvement of bone marrow was suggested, but differential diagnosis included rhabdomyosarcoma, Ewingıs tumor, or teratoma. The patient had an endovaginal ultrasound which demonstrated a complex hyperechoic mass in this region.


Three-phase bone scintigraphy includes radionuclide angiogram over the region of interest followed by immediate static images and delayed static images approximately 2-3 hours after the initial injection of radiopharmaceutical. These three-phase scintigraphic techniques improve the specificity of bone scintigraphy. The differential is between osteomyelitis vs cellulitis. However, if soft tissue inflammation is a prominent feature, primary bone involvement may be difficult to distinguish from increased activity in the bone secondary to hyperemia from an overlying simple cellulitis. Possible false- negative studies include an early stage of the disease. Further evaluation for osteomyelitis can be obtained if osteomyelitis is strongly clinically suspected with gallium-67 scintigraphy. If the uptake of gallium in the region of suspected osteomyelitis is greater than the uptake of the bone agent, osteomyelitis is probable. Acute hematogenous osteomyelitis occurs more commonly in children than in adults. These cases usually occur in the metaphysis of the long bones. This is felt to be secondary to the vascular anatomy in the metaphysis of the long bones. Children older than 1 year, but prior to skeletal maturity have no vessels crossing the physeal growth plates. Vessels approaching the physis from the nutrient foramen in the diaphysis of the long bones ramify at the level of the physeal growth plates and undergo a 180 degree bend back towards the diaphysis. At this point, there is turbulence of blood flow, which is postulated to be a cause for the increased incidence of osteomyelitis in the metaphysis. In children less than 1 year of age, a feeding vessel can span the physis and epiphyseal osteomyelitis occurs with a greater frequency in this age group. Sometimes, an antecedent history of trauma can be elicited. The antecedent history of trauma is postulated to be a predisposing factor for osteomyelitis by marrow edema in the end of the bones and an increase in pressure of the marrow space which results in decrease in blood flow in this region. The usual findings of osteomyelitis are increased activity in blood flow, blood pool, and delayed images. However, cold defects can be demonstrated due to increased pressure in the marrow space reducing blood flow, stripping away of periosteum due to pus, and interruption of blood supply by sludge and thrombosis of the nutrient vessels.

References: 1) Mettler FA. Essentials of Nuclear Medicine Imaging. 1991, 3rd edition. 2) Datz FL. Handbook of Nuclear Medicine, Mosby Yearbook Publishers, 1993, 2nd edition.


The patient underwent intraoperative ultrasound in the operating room under anesthesia and transperineal biopsy of the hyperechoic lesion demonstrated by the endovaginal ultrasound. Several passes were made in this patient and findings of necrotic abscess were demonstrated. The patient was placed on antibiotics with prompt improvement of symptoms.

Major teaching point(s):

The three-phase bone scintigraphy identified increased activity in the superior pubic ramus although the inferior pubic ramus was the area questioned on the plain radiographs. Abnormal marrow signal is demonstrated in both the inferior and superior pubic rami on the MRI study. The patient had a documented E coli infection approximately four weeks prior to the bone scintigraphy. Cultures of the abscess demonstrated Staphylococcus aureus, which is the most common cause of osteomyelitis.

Differential Diagnosis List

Soft tissue tumor such as rhabdomyosarcoma or Ewingıs sarcoma might also show increased activity on all three phases of three-phase bone scintigraphy.

ACR Codes and Keywords:

References and General Discussion of Bone Scintigraphy (Anatomic field:Skeletal System, Category:Inflammation,Infection)

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Case number: bs037

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