Relevance of [18F]FDG-PET/CT in the detection of colon pathology, in patients studied by bacteriemia or infectious endocarditis caused by enteropathogenic microorganisms.

PURPOSE: Association between S. gallolyticus infective endocarditis (IE) and malignant lesions of the gastrointestinal tract is well described. We hypothesize that other enteropathogenic microorganisms, such as S. viridans and E. faecalis are also related with colorectal pathology. Our aim is to determine the frequency of focal colorectal FDG deposits, suggestive of tumoral lesions and their correlation with colorectal pathology, in patients with infection caused by different commensal microorganisms of the gastrointestinal tract. METHODS: We retrospectively examined 61 patients diagnosed with bacteremia (BSI) and IE (possible or definite) according to Duke's criteria, caused by enteropathogenic microorganisms, who underwent a full-body [18F]FDG-PET/CT in our institution. We looked for colorrectal FDG deposits and morphological lesions. All IE patients underwent a complete colonoscopy and the histological results were classified into four groups: malignant lesion, premalignant lesion, benign lesion and no lesion. We evaluated the correlation between the findings of the [18F]FDG-PET/CT with the histopathological diagnosis and the involved microorganism. RESULTS: PET/CT detected 20 colorectal FDG deposits (32.79%-OR: 47.28), 2 within bacteriemic patients (16.7%) confirmed as malignant and premalignant lesions and 18 in IE group (36.6%), 17 of them corresponding to colorrectal pathology: 11 malignant, 5 premalignant and 1 benign lesions. In the IE subgroup, the colonoscopy detected colorectal lesions in 51.02% of the patients: 11malignant, 8premalignant and 6benign. We found a higher incidence of colorectal FDG deposits in Streptococcus spp. subgroup. Regarding the anatomopathological colonic findings there was a predominance of patients affected by S. viridans, followed by E. faecalis and S. gallolyticus. CONCLUSION: Patients studied by PET/CT for systemic infection, especially IE, caused by S. viridans or E. faecalis, in addition to S. gallolyticus, show a greater probability of presenting incidental colorectal FDG deposits, mostly corresponding to malignant or pre-malignant lesions. Therefore, it is necessary to carry out an exhaustive search of possible colorectal foci in these exams.

Hypermetabolic abdominal and cervical lymph nodes mimicking Hodgkin lymphoma relapse on FDG PET/CT after adenovirus-vectored COVID-19 vaccine.

Vaccine-associated hypermetabolic lymphadenopathy (VAHL) has been reported as a common post-vaccination side effect, especially with mRNA-based COVID-19 vaccines. Most VAHL cases present normal or enlarged regional lymph nodes close to the injection site, usually with mild-moderate FDG (18 F-Fluorodeoxyglucose) uptake on FDG positron emission tomography (PET)/CT. Here, we describe the case of a 33-year-old woman with past history of Classic Hodgkin Lymphoma (CHL) who underwent follow-up FDG PET/CT 3 days (d) after the first dose of the adenovirus-vectored Oxford-AstraZeneca COVID-19 vaccine. FDG PET/CT showed unexpected small hypermetabolic cervical and abdominal lymph nodes in the same location as at the onset of the disease, suggesting radiological relapse. Considering temporal relationship and other cases of VAHL, a new image was performed 2 months later, which revealed decreased lymph nodes and normalization of FDG uptake. This case illustrates that the possibility of a false-positive should always be considered by physicians in this new context, even when hypermetabolic lymph nodes appear far from the vaccination site.

Prevalence of biliary acid malabsorption in patients with chronic diarrhoea of functional characteristics: a prospective study.

BACKGROUND: Bile acid malabsorption occurs in up to one third of patients with chronic diarrhoea of functional characteristics. The gold standard test for its diagnosis is the 75Selenium homocholic acid taurine (75SeHCAT) test. The aim of this work is to confirm previous data suggesting that bile acid malabsorption, diagnosed by 75Se-HCAT test, is the underlying cause of diarrhoea in a significant proportion of patients previously diagnosed with a functional disorder. In addition, we have analysed the clinical response of bile acid sequestrants in those patients with a bile acid diarrhoea diagnosis. METHODS: This is a prospective, single-centre study including consecutive adult patients diagnosed with chronic diarrhoea of unknown origin and with functional characteristics; systematic rule out of common causes of chronic diarrhoea was performed before bile acid malabsorption evaluation by 75SeHCAT scanning. A retention percentage less than 10% was considered positive. Clinical response to cholestyramine was further evaluated in those patients with a positive diagnosis of bile acid diarrhoea RESULTS: 38 patients (20 male, mean age 37.5 years) were finally included. Twenty (52.6%) patients included had a positive 75SeHCAT test. Median body mass index was significantly higher in those patients. We did not find significant differences in other clinical or biochemical variables 75SeHCAT-positive and 75SeHCAT-negative groups. Only 6 of 17 (35.3%) patients responded to cholestyramine treatment; 10 patients did not have response or withdraw the drug due to adverse events. Logistic regression analysis showed that none of the included variables was a predictor of clinical response to cholestyramine. CONCLUSIONS: Bile acid malabsorption occurs in a high proportion of patients suffering from chronic diarrhoea with functional characteristics. Systematic investigation of bile acid malabsorption should be included in the diagnostic algorithms of patients with chronic watery diarrhoea in the routine clinical practice. Absence of response to cholestyramine does not rule out bile acid diarrhoea.

Clinical utility of (18)F-fluorocholine positron-emission tomography/computed tomography (PET/CT) in biochemical relapse of prostate cancer after radical treatment: results of a multicentre study.

OBJECTIVE: To evaluate (18)F-fluorocholine positron-emission tomography (PET)/computed tomography (CT) in restaging patients with a history of prostate adenocarcinoma who have biochemical relapse after early radical treatment, and to correlate the technique's disease detection rate with a set of variables and clinical and pathological parameters. PATIENTS AND METHODS: This was a retrospective multicentre study that included 374 patients referred for choline-PET/CT who had biochemical relapse. In all, 233 patients who met the following inclusion criteria were analysed: diagnosis of prostate cancer; early radical treatment; biochemical relapse; main clinical and pathological variables; and clinical, pathological and imaging data needed to validate the results. Criteria used to validate the PET/CT: findings from other imaging techniques, clinical follow-up, treatment response and histological analysis. Different statistical tests were used depending on the distribution of the data to correlate the results of the choline-PET/CT with qualitative [T stage, N stage, early radical prostatectomy (RP) vs other treatments, hormone therapy concomitant to choline-PET/CT] and quantitative [age, Gleason score, prostate-specific antigen (PSA) levels at diagnosis, PSA nadir, PSA level on the day of the choline-PET/CT (Trigger PSA) and PSA doubling time (PSADT)] variables. We analysed whether there were independent predictive factors associated with positive PET/CT results. RESULTS: Choline-PET/CT was positive in 111 of 233 patients (detection rate 47.6%) and negative in 122 (52.4%). Disease locations: prostate or prostate bed in 26 patients (23.4%); regional and/or distant lymph nodes in 52 (46.8%); and metastatic bone disease in 33 (29.7%). Positive findings were validated by: results from other imaging techniques in 35 patients (15.0%); at least 6 months of clinical follow-up in 136 (58.4%); treatment response in 24 (10.3%); histological analysis of lesions in 17 (7.3%); and follow-up plus imaging results in 21 (9.0%). The statistical analysis of qualitative variables, corresponding to patients' clinical characteristics, and the positive/negative final PET/CT results revealed that only whether or not early treatment with RP was done was statistically significant (P < 0.001), with the number of positive results higher in patients who did not undergo a RP. Among the quantitative variables, Gleason score, Trigger PSA and PSADT clearly differentiated the two patient groups (positive and negative choline-PET/CT: P = 0.010, P = 0.001 and P = 0.025, respectively). A Gleason score of <5 or ≥ 8 clearly differentiated positive from negative PET. Trigger PSA: mean of 8 ng/mL for positive PET/CT vs 2.8 ng/mL for negative PET/CT; PSADT: mean of 8 months for positive vs 12.6 months for negative. The optimal threshold values were: 3 ng/mL for Trigger PSA level and 6 months for PSADT (Youden index/receiver operating characteristic curve). Analysing these two variables together showed that PSADT was more conclusive in patients with lower Trigger PSA levels. Analysing variables by location showed that only PSADT was able to differentiate between those with disease confined to the prostate compared with the other two locations (lymph nodes and bone), with shorter PSADT in these two, which was statistically significant (P < 0.002). In the patient group with a PSA level of <1.5 ng/mL, 30.8% had the disease, 7% of whom had metastatic bone disease. In the multivariate logistic regression, the risks factors that were clearly independent for those with positive PET/CT were: PSA level of >3 ng/mL, no early RP, and Gleason score of ≥ 8. CONCLUSION: Our results support the usefulness of (18)F-fluorocholine PET/CT in biochemical relapse of prostate cancer after radical treatment, with an overall disease detection rate close to 50%, and it can be recommended as first-line treatment. As mentioned above, besides Trigger PSA levels, there are other clinical and pathological variables that need to be considered so as to screen patients properly and thus minimise the number of nodular lesions and increase the diagnostic accuracy of the examination.

Small rounded B-cell lymphoma of bone presented by limp, with a positive multifocal 99mTc MDP bone scintigraphy pattern and a negative 99mTc HMPAO-labeled leukocytes study.

In this article, we present a rare case of B-cell bone lymphoma in a child with multifocal asymptomatic lesions detected by bone scintigraphy and a chronic clinical history characterized by limping and fever episodes for over a year. Initially, multifocal osteomyelitis was suspected and antibiotic therapy was administered with no clinical improvement. The biopsy of the main lesion in the left distal femur along with bone marrow cytology established the final diagnosis. This rare case illustrates the utility of routinely low cost-effective nuclear medicine studies like whole body bone scan and 99mTc hexamethylpropyleneamine oxime-labeled leukocytes to orientate similar cases to a correct diagnosis.