Active ulcerative colitis diagnosed by (18)F-FDG PET/CT in an anti-TNF alpha treated patient with no visible luminal lesions on colonoscopy

PET/MR enterography in inflammatory bowel disease: A review of applications and technical considerations

Positron emission tomography (PET) magnetic resonance (MR) enterography is a novel hybrid imaging technique that is gaining popularity in the study of complex inflammatory disorders of the gastrointestinal system, such as inflammatory bowel disease (IBD). This imaging technique combines the metabolic information of PET imaging with the spatial resolution and soft tissue contrast of MR imaging. Several studies have suggested potential roles for PET/MR imaging in determining the activity status of IBD, evaluating treatment response, stratifying risk, and predicting long-term clinical outcomes. However, there are challenges in generalizing findings due to limited studies, technical aspects of hybrid MR/PET imaging, and clinical indications of this imaging modality. This review aims to further elucidate the possible role of PET/MR in IBD, highlight important technical aspects of imaging, and address potential pitfalls and prospects of this modality in IBDs.

Assessment of incidental focal colorectal uptake by analysis of fluorine-18 fluorodeoxyglucose positron emission tomography parameters

BACKGROUND

Colon and rectal cancers are among the top five cancers worldwide in terms of their incidence and mortality rates. As the treatment options for cure include surgery even in specific advanced-stage cases, the early detection of lesions is important for applying active treatment methods. Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) is an established imaging study for many types of cancers; however, physiologic uptake in the gastrointestinal tract is a frequent finding and may interfere with lesion identification. Nevertheless, as unexpectedly observed focal colorectal F-18 FDG uptake may harbor malignant lesions, further examination must not be avoided.

AIM

To assess the clinical implications of unexpected focal colorectal F-18 FDG uptake by analyzing FDG PET parameters.

METHODS

A total of 15143 F-18 FDG PET/CT scans performed at our hospital between January 2016 and September 2021 were retrospectively reviewed to identify incidentally observed focal colorectal FDG uptake. Finally, 83 regions showing focal colorectal FDG uptake with final histopathological reports from 80 patients (45 men and 35 women with mean ages of 66.9 ± 10.7 years and 63.7 ± 15.3 years, respectively) were eligible for inclusion in the present study. Each focal hypermetabolic colorectal region was classified as malignant, premalignant, or benign according to the histopathological report. PET parameters such as maximum and peak standardized uptake value (SUVmax and SUVpeak), metabolic tumor volume (MTV), mean SUV of the metabolic tumor volume (mSUVmtv), and total lesion glycolysis (TLG) were measured or calculated for the corresponding hypermetabolic regions. Parametric and non-parametric statistical comparisons of these parameters were performed among the three groups. Receiver operating characteristic curves were plotted to identify cut-off values.

RESULTS

The detection rate of incidental focal colorectal uptake was 0.53% (80/15,143). Of the 83 regions with unexpected focal colorectal hypermetabolism, 28.9% (24/83) were malignant, 32.5% (27/83) were premalignant, and 38.6% (32/83) were benign. Overall, 61.4% of the regions had malignant or premalignant lesions. SUVmax, SUVpeak, and mSUVmtv differentiated malignant and/or premalignant lesions from benign lesions with statistical significance (P < 0.05). mSUVmtv3.5 differentiated malignant from benign lesions, with the largest area under the curve (AUC) of 0.792 and a cut-off of 4.9. SUVmax showed the largest AUC of 0.758 with a cut-off value of 7.5 for distinguishing between premalignant and benign lesions. Overall, SUVmax with a cut-off value of 7.6 (AUC: 0.770, 95% confidence interval (CI): 0.668-0.872; sensitivity, 0.686; specificity, 0.688) was a superior parameter for distinguishing between malignant/premalignant and benign lesions or physiologic uptake. No parameters differentiated malignant from premalignant lesions. Moderate or weak positive correlations were observed between the long diameter of the malignant lesions and PET parameters such as SUVpeak and some mSUVmtv.

CONCLUSION

Approximately two-thirds (61.4%) of incidental focal hypermetabolic colorectal regions were malignant/premalignant lesions, for which SUVmax was an independent diagnostic parameter. Unexpected suspicious focal colorectal FDG uptake should not be avoided and consideration for further evaluation is strongly recommended not to miss the two-thirds.

FDG-PET/CT in Inflammatory Bowel Disease: Is There a Future?

FDG-PET/CT has potential in inflammatory bowel disease. The literature generally presents good sensitivity and specificity in various settings. At present, the most promising roles are assessment of early treatment response and stricture characterization, whereas general use in the initial diagnostic workup should be reserved for equivocal cases for the time being. However, it is challenging to image the moving and physiologically active bowel with FDG, and available literature is far from ideal. Thus, several issues remain unclarified, and further data are needed to make firm conclusions on the role of FDG and PET/CT in inflammatory bowel disease.

Follicular lymphoma-related colitis resembling ulcerative colitis

Among the various manifestations of colonic involvement in malignant lymphomas, an ulcerative colitis-like appearance is rare. Herein, we describe a case in which extranodal colonic involvement resembled ulcerative colitis in a patient with advanced follicular lymphoma. A 59-year-old Japanese man with diarrhea and body weight loss was referred to our hospital. Computed tomography (CT) revealed systemic lymphadenopathy, splenomegaly, and thickening of the sigmoid colon and rectum walls. ¹⁸F-fluorodeoxy-glucose positron emission tomography (¹⁸F-FDG-PET/CT) revealed intense tubular ¹⁸F-FDG accumulation extending from the rectum to the colon at the hepatic flexure and much weaker accumulation in the systemic lymph nodes, bone marrow, and spleen. The isotope-enriched areas had an ulcerative colitis-like appearance as shown via colonoscopy. The patient was ultimately diagnosed with follicular lymphoma (stage IV A, grade 1) based on a pathological examination of the neck lymph nodes, iliac bone marrow, and colon. After six courses of chemotherapy (R-CHOP), ¹⁸F-FDG-PET/CT confirmed complete remission of the lymphoma including the colonic lesion. This is presumably the first case of ulcerative-like colitis caused by a follicular lymphoma. As a novel approach, the lymphoma-related colitis was detected by comparing the pathology results and the ¹⁸F-FDG-PET/CT results.

Surgical management of ulcerative colitis in the era of biologicals

PURPOSE

Proctocolectomy has been a curative option for patients with severe ulcerative colitis. In recent years, there has been a growing use of medical salvage therapy in the management of patients with moderate to severe ulcerative colitis. We aimed at reviewing the role of surgical management in a time of intensified medical management on the basis of published trial data. The aim was to determine the efficacy of aggressive medical versus surgical management in achieving multifaceted treatment goals.

METHODS

A comprehensive search of Pubmed, Medline, the Cochrane database was performed. Abstracts were evaluated for relevance. Selected articles were then reviewed in detail, including references. Recommendations were then drafted based on evidence and conclusions in the selected articles.

RESULTS

The majority of patients with UC will not need surgery. However, steroid-refractoriness and steroid-dependence signal a subset of patients with more challenging disease. Biological therapy has been shown to achieve short-term improvement and temporarily reduce the need for a colectomy. However, there is a substantial financial and medical price to pay because a high fraction of these salvaged patients will still need a curative colectomy but may be exposed to the negative impact of prolonged immunosuppression, chronic illness, and a higher probability to require 3 rather than 2 operations. Proctocolectomy with ileo-anal pouch anastomosis-performed in 1, 2, or 3 steps depending on the patient's condition-remains the surgical procedure of choice. Even though it has its share of possible complications, it has been associated with excellent long-term outcomes and high levels of satisfaction, such that in the majority of patients they become indistinguishable from unaffected normal individuals.

CONCLUSIONS

The current data demonstrate that use of medical salvage therapy in the treatment of UC will likely continue to grow and evolve. Consensus is being developed to better define and predict failure of medical therapy and clarify the role of the different treatment modalities. For many patients, sacrificing the nonresponsive diseased colon is an underused or unnecessarily delayed chance to normalize their health and life. Biologicals in many instances may have to be considered the bridge to that end.