Acute experimental osteomyelitis and abscesses: detection with MR imaging versus CT

Acute experimental osteomyelitis and abscesses were induced in the proximal tibia and surrounding soft tissues, respectively, in 67 New Zealand white rabbits. Fifty-three rabbits were injected with a Staphylococcus aureus solution and 26, with sterile saline in tibial medullae and/or surrounding soft tissues. Contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging were performed 7 days after inoculation. Immediately after imaging, the animals were killed and necropsy was performed. MR imaging was more sensitive than CT in the detection of osteomyelitis (94% vs 66%, P less than .025) and abscesses (97% vs 52%, P less than .001). MR imaging was equally specific as CT in the exclusion of osteomyelitis (93% vs 97%, chi 2 = 0) but less specific than CT in the exclusion of abscesses (77% vs 100%, P less than .025). The overall accuracy of MR imaging was somewhat, although not significantly, greater than that of CT in the detection of both osteomyelitis (93% vs 80%) and abscesses (87% vs 75%).     

Gas distribution in intraabdominal and pelvic abscesses on CT is associated with drainability

OBJECTIVE: Intraabdominal and pelvic abscesses are treated by percutaneous image-guided drainage, under sedation or general anesthesia. This study attempts to determine if the CT features of gas distribution are associated with "drainability." Our premise was that gas may be trapped deep in a collection as bubbles, if the material is thick. Gas may rise to the surface if the material is thin, forming either an air-fluid level or superficial bubbles. MATERIALS AND METHODS: Patients with intraabdominal and pelvic abscesses were identified by the interventional radiology database, after research ethics board approval. Patients without prior CT were excluded. The imaging and clinical records were analyzed retrospectively. Intracollection gas distribution was recorded as superficial bubbles, deep bubbles, or air-fluid levels. Collections were classified accordingly: type 1, air-fluid levels; type 2, superficial or deep bubbles and air-fluid levels; type 3, superficial bubbles; type 4, deep bubbles; and type 5, no gas. RESULTS: One hundred five abscesses were examined in 61 patients, ranging in age from 2-17 years. Eight of 8 of type 1, 16 of 16 of type 2, 19 of 21 of type 3, 8 of 13 of type 4, and 43 of 47 of type 5 were drainable. The abscesses of all patients with an air-fluid level were drainable. Of abscesses with deep bubbles, 61.5% were drainable, versus 90.5% of those with superficial bubbles. Of those with superficial gas (superficial bubbles or air-fluid levels), 95.6% were drainable. In comparison with superficial gas, abscesses with deep trapped gas were associated with a longer duration of drainage, longer hospital stay, lower percentage of successful drainage, and higher percentage of residual collections. The difference is significant for drainability (p = 0.0048; p = 0.0331 after statistical adjustment for multiple testing). CONCLUSION: Distribution of gas in an intraabdominal or pelvic abscess is associated with drainability. Abscesses with superficial gas (superficial bubbles or air-fluid levels) have a greater chance of being drained successfully than do abscesses with deep trapped gas.     

CT detection and aspiration of abdominal abscesses.

Computed tomography (CT) is effective in detecting intraabdominal abscesses. Loculations of fluid and extraluminal gas are clearly localized in relation to other organs. Of 22 abscess in this series, CT successfully detected 20; comparative information with gallium, techneticum, and ultrasound scans is presented. In addition to localizing these collections, CT can be used to guide needle aspiration and drainage procedures. Three sizes of needles were used to aspirate specimens and/or provide drainage. This was accomplished successfully in 12 of 14 CT-guided procedures.     

CT of sacral injury

Eighty-eight patients with 188 sacral fractures were examined with computed tomography (CT) and conventional radiography. Four main patterns of sacral injury were defined: sacroiliac diastasis (39%), sacral and/or iliac lip fractures (25%), vertical shear fractures (25%), and comminuted fractures (5%). Initial interpretation of plain radiographs failed to define 29% of the sacroiliac joint diastases, 57% of the lip fractures, 34% of the vertical shear fractures, and 25% of the comminuted fractures. The extent of injury was better delineated with CT, and a more certain diagnosis of sacral injury was possible with CT than with radiography. Because of the higher detection rate and improved imaging of fracture configuration, CT should be performed in all patients with sacral injury.     

Ectopic ovaries associated with absent uterus and pelvic kidney: CT findings

A patient with a congenitally absent uterus and a single pelvic kidney presented with recurrent pain in the left iliac fossa. This proved to be due to a prolapsed left ovary.     

The detection of abscesses with diffusible tracers

In six patients with suspected infection, scintigraphy with diffusible tracers outlined the margins and central portion of an abscess. An animal model was developed to study this process quantitatively. Small inflammatory lesions yielding volumes of pus of 0.1-0.2 mL were shown to have increased blood volume of 0.7 +/- 0.5 mL, increased blood flow by a factor of three and increased extracellular fluid volume of 10 +/- 6 mL. This supports the patient data and indicates that the pathophysiologic features characterising the clinical studies are hyperemia and oedema associated with an abscess. The slow, central area of tracer diffusion corresponded to the presence of pus. Scintigraphy with 99mTc-DTPA is a convenient way of detecting suspected inflammatory lesions and localising collections of pus.     

CT detection of serious internal and skeletal injuries in patients with pelvic fractures

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the percentage of patients with known pelvic fractures who have additional findings of intraabdominal injury, as diagnosed at abdominal computed tomography (CT), and to determine if patients with specific types or patterns of fractures are more likely to have additional injuries. MATERIALS AND METHODS: The authors reviewed the medical records of 200 consecutive patients (125 women, 75 men; age range, 4-86 years) who had been admitted to a level 1 trauma center with osseous pelvic injury secondary to blunt trauma and who had undergone abdominal CT examinations. Abdominal CT findings in these patients were classified as negative, positive, or minimal and correlated with mechanism of pelvic fracture. RESULTS: Sixty-five (32%) of the 200 patients had negative CT findings, 43 (22%) had findings attributable to the trauma but required no follow-up, and 92 (46%) had positive findings that required nonsurgical management or exploratory laparotomy. Additional pelvic fractures were identified in 63 (32%) patients. The highest prevalence of additional injuries was in patients with Malgaigne fractures (four of 15, 27%) or bilateral pubic rami fractures (six of 18, 33%). CONCLUSION: CT examinations revealed that 135 (68%) of 200 patients with pelvic fractures secondary to blunt trauma had concomitant internal or skeletal injuries and that 92 (46%) patients had injuries severe enough to require nonsurgical management or exploratory laparotomy. Patients with bilateral pubic rami fractures or Malgaigne fractures were particularly prone to additional injuries; therefore, abdominal CT examinations are recommended in these patients.     

CT characteristics of traumatic sacral fractures in association with pelvic ring injuries: correlation using the Young-Burgess classification system

Purpose

The purpose of the study is to determine the incidence of sacral fracture patterns on CT imaging of pelvic trauma patients with correlation with mechanism of injury and pelvic ring injury pattern using the Young-Burgess classification system.

Materials and methods

This is a retrospective review of all pelvic CTs with pelvic fractures performed at our level 1 trauma center during a 4-year period from July 2010 to June 2014.

Results

Sacral fractures were very common in pelvic trauma patients, being present in 60% of patients presenting to our institution with pelvic fractures. Longitudinal fractures were almost always associated with additional pelvic ring injuries. Denis zone 1 fractures had the highest association with lateral compression pelvic ring injuries. Denis zone 2 and 3 fractures were seen with increased frequency in AP compression and vertical shear injuries. A third of transverse sacral fractures occurred in isolation, with isolated transverse sacral fractures typically occurring in the low (S3–S5) sacrum. Almost half of combined transverse and longitudinal sacral fractures occurred without an additional pelvic fracture present. Sacral avulsions almost always occurred as part of a pelvic ring fracture pattern, most commonly in AP compression injuries. Coccyx fractures frequently occurred in isolation, but were commonly seen in vertical shear injuries when associated with a pelvic ring injury pattern.

Conclusion

Avulsion fractures and longitudinal fractures of the sacrum are almost always associated with anterior pelvic ring injury. Conversely, transverse fractures of the lower sacrum and combined longitudinal and transverse sacral fractures are prone to occur in isolation.

     

Deep pelvic abscesses: transrectal drainage with radiologic guidance.

Transrectal catheter drainage was performed under radiologic guidance in eight patients with deep pelvic abscesses during a 7-month period. One patient underwent two procedures. In five patients, the abscess could not be palpated at rectal examination. Seven procedures were performed with fluoroscopic guidance. Transrectal ultrasound was performed in conjunction with fluoroscopy for two procedures. Medium to large (8-14-F) locking catheters were used in seven procedures, and small (5-F) nonlocking pigtail catheters were used in two. The catheter was left in place for 3 days or less in all but one patient, in whom the catheter was left in place for 20 days. Five abscesses were drained through the anterior or anterolateral rectal wall and four, including one repeat drainage, through the posterior rectal wall. No complications occurred as a direct result of transrectal drainage. Successful initial drainage was established with clinical improvement in all cases. Two patients eventually required surgery, one for continued bleeding into an infected hematoma and one for abscess recurrence after tube dislodgment. Transrectal drainage performed with radiologic guidance is a safe, feasible procedure; is well tolerated by patients; and is relatively easy to perform with the techniques described.     

Differentiation between pelvic abscesses and pelvic tumors with diffusion-weighted MR imaging: a preliminary study

PurposeUse diffusion-weighted magnetic resonance imaging (MRI) in differentiating pelvic abscess from pelvic cystic tumor.Materials and methodsPatients with pelvic abscess (n=23) or pelvic cystic tumor (n=15) who underwent diffusion-weighted MRI were reviewed.ResultsPelvic abscesses showed hyperintensity on diffusion-weighted MRI and hypointensity on apparent diffusion coefficient (ADC) map. The mean ADC values of fluid in pelvic abscess and pelvic tumors were 0.73±0.15×10^?3 and 2.27±0.45×10^?3 mm²/s, respectively. Pelvic abscesses had significantly lower ADC values than pelvic cystic tumors (P<.001).ConclusionDiffusion-weighted MRI provides a noncontrast method for interpreting pelvic cystic lesions.     

CT detection of retroperitoneal gas associated with gas in intervertebral disks

Three cases are presented with computed tomographic evidence of gas in retroperitoneal soft tissues in association with the so-called "vacuum phenomenon" (Knutsson sign) in lumbar disks. We review the explanations of Knutsson sign and offer an explanation of how extradiscal gas can occur in association with it.     

Dynamic CT features of hepatic abscesses

Forty hepatic abscesses were examined with dynamic computed tomography (CT). A "double target sign," consisting of a hypodense central area surrounded by first a hyperdense ring and then a hypodense zone, seems to be highly suggestive of abscess formation. In 12 cases, the hepatic parenchyma surrounding the lesion demonstrated transient hyperdensity after contrast injection, possibly due to localized hepatic venous obstruction secondary to acute hepatic inflammation. This is similar to the appearance of an arterioportal fistula.     

Pedal abscesses in patients suspected of having pedal osteomyelitis: analysis with MR imaging

PURPOSE: To document the expected frequency, location, and size of pedal abscesses in patients with advanced foot infection. MATERIALS AND METHODS: Images obtained at contrast material-enhanced magnetic resonance (MR) imaging (at 1.5 T) of 161 feet of 51 women and 107 men (mean age, 58.5 years; 82.3% had diabetes) who underwent bone biopsy after MR imaging for possible osteomyelitis were reviewed by two musculoskeletal radiologists working together. Presence, size, and location of abscesses and presence of adjacent skin ulceration were noted. MR imaging criteria for abscess were the following: presence of fluid collection with isointense or hypointense signal on T1-weighted images, fluid-equivalent signal intensity on T2-weighted images, and peripheral rim enhancement. All patients' charts were reviewed for clinical and surgical information. RESULTS: Thirty-two fluid collections compatible with abscesses were found in 29 (18.4%) of the 158 patients; 26 (90%) of these patients had diabetes (P =.38). Abscess size varied from 1 x 0.5 x 0.4 cm to 3.8 x 3.4 x 2.2 cm (mean = 2.6 x 1.5 x 0.9 cm). Abscesses were located in the forefoot (n = 15), hindfoot (n = 7), toes (n = 3), midfoot (n = 4), or in multiple locations (n = 3). Thirty-one abscesses (97%) occurred near a skin ulcer (distance range, 0-9.1 cm; mean, 1.4 cm). Abscesses were significantly more frequent in patients with osteomyelitis (n = 28, 97%) (P <.001) and in feet that had been treated surgically (n = 16, 33%) (P <.002). CONCLUSION: MR imaging revealed abscesses, predominantly in the forefoot, in 18% of patients suspected of having pedal osteomyelitis. Abscesses are significantly more frequent in patients with osteomyelitis and in feet that have been treated surgically.     

MRI and pelvic abscesses: a pictorial review

OBJECTIVE: The purpose of our article was to review the magnetic resonance imaging (MRI) features of pelvic abscesses. Pelvic abscesses account for a wide range of abnormalities from various etiologies. CONCLUSION: MRI is being increasingly used for pelvic exploration. Radiologists must thus be aware of their features and characteristics.     

Specific enhancement of intra-abdominal abscesses with perfluoroctylbromide for CT imaging

Perfluoroctylbromide (PFOB), a radiopaque reticuloendothelial system contrast media for computed tomography, has been shown to accumulate in macrophages. In the current study PFOB was tested in rabbits as an abscess imaging agent. Two abscesses were induced in each of 24 rabbits, one in the liver and the other in the peritoneal cavity. CT of the rabbit abdomen was performed four days later, two days after the administration of 5 gm/Kg of PFOB to 12 of these rabbits. The average enhancement of the wall of liver abscesses was by 140 Hounsfield units (HU) relative to the enhanced liver and peritoneal abscesses by 135 HU relative to the control group. This enhancement was secondary to the intense accumulation of PFOB filled macrophages in the abscess wall. In those rabbits where the liver abscess ruptured, the edges of the peritoneal collections enhanced by 147 HU. Regions of inflammation prior to liquifaction enhanced considerably. These areas could not be detected in the animals not receiving PFOB. Though the liquified center of liver abscesses could be seen in the absence of PFOB, none of the peritoneal abscesses could be detected in the animals not receiving PFOB. In contradistinction, all peritoneal abscesses enhanced considerably following PFOB allowing their prospective localization. In conclusion, PFOB accumulates in abscess walls and areas of inflammation producing marked CT enhancement of liver and peritoneal abscess collections. This enhancement allowed the differentiation of peritoneal abscess collections from adjacent bowel.