F-18 FDG positron emission tomographic imaging in bilateral iliopsoas abscesses

Evaluation of therapeutic response of tuberculoma using F-18 FDG positron emission tomography

BACKGROUND

Monitoring the response to antituberculosis (anti-TB) treatment can be difficult in patients with tuberculoma. We have retrospectively assessed the ability of F-18 fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) to evaluate the response to anti-TB treatment in patients with tuberculoma.

METHODS

Two patients with tuberculoma underwent repeat PET scans during anti-TB treatment. Changes in maximal standard uptake value (SUV) of the tuberculoma on PET images were analyzed between 2 scans. Initial PET scans were performed before the start of anti-TB treatment (T0), and later scans were performed after completion of treatment (T1).

RESULTS

In a 57-year-old female patient with clinical TB, maximal SUV of tuberculoma on PET scan decreased from 2.6 (at T0) to an undetectable value (at T1) at an interval of 187 days. In a 60-year-old woman with biopsy-proven TB, maximal SUV of tuberculoma on PET scan decreased from 4.8 (at T0) to 1.1 (at T1) at an interval of 192 days.

CONCLUSION

PET scans may be useful for monitoring responses to anti-TB treatment in patients with tuberculoma.

Psoas abscess - not as rare as we think?

OBJECTIVE

Iliopsoas abscess (IPA) is a rare condition with a reported worldwide incidence of 12 new cases per year with primary abscesses now predominating. The presentation is often vague and the diagnosis not considered.

METHOD

The medical records of 15 consecutive patients presenting to our hospital in a 3-year period with IPA were reviewed. Demographic data, presenting features, predisposing factors and the investigations performed were recorded. Abscesses were classified as primary or secondary and the treatment provided and eventual outcomes were analysed.

RESULTS

Fifteen patients (eight males) were included. Nine patients were pyrexial on admission, 14 were anaemic and all had raised inflammatory markers. Only five patients presented with the classical triad of pain, fever and limp. The median time to diagnosis was 3 days with a median hospital stay of 27 days (range 7-243 days). Fourteen patients were diagnosed by computed tomographic scan. Three patients were treated with antibiotics alone whilst 11 received percutaneous drainage (PCD) as well. Of these, five had recurrence following initial drainage, needing further PCD procedures but none needed open drainage. Only one patient underwent open drainage initially. The mortality rate was 20%.

CONCLUSION

The incidence of IPA is probably under-reported. The vague presentation leads to delays in diagnosis and increases morbidity and a high index of suspicion is the key to early diagnosis. Percutaneous drainage with antibiotics is the first line of treatment although recurrence rate is high. Open drainage allows simultaneous treatment of underlying pathology in secondary abscesses.

Cold tuberculous abscess identified by FDG PET

We report FDG PET of two cases of cold abscess due to Mycobacterium tuberculosis. Case 1 had colon cancer; FDG PET showed high FDG uptake in the colon lesion and low uptake in the inguinal lesion. The latter was a tuberculous cold abscess confirmed by CT/MRI and biopsy. Case 2 received radiotherapy for lung cancer and presented with suspected vertebral metastasis. Further studies revealed tuberculosis of the vertebra and a tuberculous cold abscess in the iliopsoas muscle. FDG PET showed moderate uptake in the third lumbar spine and low uptake in the abscess center of iliopsoas lesion. Both tuberculous cold abscesses showed moderate FDG uptake in the capsule and low uptake in the center. These features are unique compared with non-tuberculous abscess and typical tuberculosis lesions, which are characterized by high FDG uptake. Pathologically, tuberculous cold abscess is not accompanied by active inflammatory reaction. Our findings suggested that the FDG uptake by tuberculous lesion varies according to the grade of inflammatory activity. The new diagnostic features of tuberculous cold abscess may be useful in the evaluation of such lesions by FDG PET.

Applications of fluorodeoxyglucose-PET imaging in the detection of infection and inflammation and other benign disorders

FDG-PET has great potential in the evaluation of a variety of inflammatory and infectious disorders and possibly other benign disorders. FDG-PET is very helpful in the evaluation of chronic osteomyelitis, sarcoidosis, FUO, and differentiating toxoplasmosis from lymphoma in the central nervous system in HIV-positive patients. The assessment of efficacy of FDG-PET in the evaluation of arthroplasty-associated infection, large-vessel vasculitis, and other inflammatory and infectious disorders is ongoing but seems quite promising at this time.