Investigation of suspected intra-abdominal sepsis: the contribution of nuclear medicine

Hepato-Biliary Imaging in an Acute Setting: Is There a Role for Nuclear Medicine?

Nuclear medicine (NM) is not commonly considered as a first-line imaging modality in hepato-biliary (HB) emergencies. The aim of this review is to provide an update on the potential of NM for the imaging of HB emergencies. 99mTc-HIDA scintigraphy showed high diagnostic accuracy for acute cholecystitis, thus being particularly useful in patients at high-risk for surgery due to comorbidities and with no clear findings at US or CT. Although limitedly explored, White blood cell (WBC) scan might have a role in case of acute pancreatitis, especially for the imaging of pancreatic leukocyte infiltration and the prediction of pancreatic necrosis. Scientific literature on 18F-FDG-PET/CT in HB acute disease mainly consists of case reports or case series, describing incidental findings in oncological PET/CT scans. In patients with obstructive jaundice, PET/CT has been proposed to disclose and characterize occult tumoral etiology. Further studies are needed to evaluate the clinical usefulness of the various NM approaches in HB acute settings, particularly with respect to the emerging new technologies (eg, PET/MRI) and radiopharmaceuticals.

Diagnostic challenges in postoperative intra-abdominal sepsis in critically ill patients: When to reoperate?

The present paper was done to review common diagnostic techniques used to help surgeons find the most suitable way to diagnose postoperative intra-abdominal sepsis (IAS). The topic was searched on MEDLINE, Embase, and Cochrane Library databases. Collected articles were classified and checked for their quality. Findings of selected research were included in this study and analyzed to find the best diagnostic method for intra-abdominal sepsis. IAS presents severe morbidity and mortality, and its early diagnosis can improve the outcome. Currently, there is no consensus among surgeons on a single diagnostic modality that should be used while deciding reoperation in patients with postoperative IAS. Though it has a high sensitivity for abdominal infections, computed tomography has limited applications due to mobility and time constraints. Diagnostic laparoscopy is a safe process that produces usable images, and can be used at the bedside. Diagnostic peritoneal lavage (DPL) has high sensitivity, and the patients testing positive through DPL can be subjected to exploratory laparotomy, depending on severity. Abdominal Reoperation Predictive Index (ARPI) is the only index reported as an aid for this purpose. Serial intra-abdominal pressure measurement has also emerged as a potential diagnostic tool. A proper selection of diagnostic modality is expected to improve the outcome in IAS, which presents high mortality risk and a limited time frame.

The labeled-leukocyte scan in the study of abdominal abscesses

AIM

The purpose of the present paper was to review the literature over the last 30 years to assess the value of radionuclide imaging, particularly labeled leukocyte scan, as compared to other imaging modalities in the management of abdominal abscesses.

METHODS

A systematic review of the published studies in humans cited in PubMed written in English, French, German, Italian, and Spanish was made.

RESULTS

Ultrasound (US) has lower sensitivity than leukocyte scan (LS), particularly in patients without localizing signs, while CT has higher sensitivity than US, but less than LS. On the other hand, CT had higher specificity than both LS and US.

DISCUSSION

LS is the more sensitive method to localize abdominal abscesses and may guide dedicated US and CT investigations to improve their diagnostic potential. Further diagnostic evolution is expected from the routine use of hybrid SPECT/CT systems.

[Hepatic abscess demonstrated by 67Ga-citrate scintigraphy within a diagnosis of fever of unknown origin]

We report a case of a 63 year old man who was seen in the hospital because of fever having a possible infectious or oncological origin. A 67Ga scintigraphy was performed and showed high pathological accumulation in the hepatic dome. The patient was re-evaluated and studied with other diagnostic tests including a CT scan, coinciding with the findings in the 67Ga-citrate scintigraphy. A correct final diagnosis of liver abscess was made.

[99mTc] liposomes for localizing experimental colitis in a rabbit model

[(99m)Tc] liposomes (TL) and [(111)In]WBCs (WBCs) were compared for imaging colitis in rabbits. At 24 h, liver was the major organ of accumulation (7.8% TL vs 39.7% WBCs), besides blood (44.1% TL vs 24.4% WBCs) and spleen (0.3% TL vs 7% WBCs). The inflamed colon accumulated 37.1 times more of [(99m)Tc] liposomes than the normal colon whereas the ratio was only 15.2 in case of [(111)In] WBCs. The study demonstrates the usefulness of [(99m)Tc] liposomes for imaging inflammatory bowel diseases.

Imaging experimental intraabdominal abscesses with 99mTc-PEG liposomes and 99mTc-HYNIC IgG

OBJECTIVE

To evaluate the accuracy of technetium-99m-labeled polyethylene glycol-coated liposomes (99mTc-PEG liposomes) and technetium-99m-labeled nonspecific human immunoglobulin G (99mTc-HYNIC IgG) for the scintigraphic detection of experimental intraabdominal abscesses in comparison with that of a standard agent, gallium-67 citrate.

BACKGROUND

Scintigraphic imaging techniques can be very useful for the rapid and accurate localization of intraabdominal abscesses. Two newly developed radiolabeled agents, 99mTc-PEG liposomes and 99mTc-HYNIC IgG, have shown to be excellent agents for imaging experimental focal infection, but have not yet been studied in the detection of abdominal abscesses.

METHODS

Intraabdominal abscesses were induced in 42 rats using the cecal ligation and puncture technique. Seven days later, randomized groups of rats received 99mTc-PEG liposomes, 99mTc-HYNIC IgG, or 67Ga citrate intravenously. The rats were imaged up to 24 hours after the injection. The biodistribution of the radiolabel was determined by counting dissected tissues ex vivo. Macroscopic intraabdominal abnormalities and focal uptake on the images were independently scored on a semiquantitative scale.

RESULTS

99mTc-PEG liposomes provided the earliest scintigraphic visualization of the abscess (as soon as 2 hours after the injection vs. 4 hours for the other two agents). Liposomes, IgG, and gallium all showed similarly high absolute uptake in the abscess. Focal uptake of liposomes and gallium correlated best with the extent of the macroscopic abnormalities.

CONCLUSIONS

99mTc-PEG liposomes and 99mTc-HYNIC IgG performed at least as well as the standard agent, 67Ga citrate, in the detection of experimental intraabdominal abscesses, with obvious advantages such as lower radiation exposure and more favorable physical properties. Of the two technetium agents, the liposomes seemed to be superior, providing the earliest diagnostic image and the best correlation with the inflammatory abnormalities. In addition, the preferential localization of radiolabeled PEG liposomes holds promise for targeted delivery of liposome-encapsulated drugs.

The technetium white cell scan as an initial imaging investigation for evaluating suspected childhood inflammatory bowel disease

BACKGROUND

The technetium white cell scan (WCS) may be a useful investigation for patients with inflammatory bowel disease (IBD). In a retrospective study we assessed the use of the WCS as an initial imaging investigation in evaluating children with suspected IBD.

METHODS

Over a 3-year period, 60 WCS were performed on 55 patients (25 boys, median age 12.1 years, age range 1.5-18 years) with known or suspected IBD. There were two clinical groups: those with previously diagnosed IBD (histologically and radiologically) and in clinical relapse (13 patients), and newly presenting patients with suspected IBD (42 patients).

RESULTS

Eighteen scans were performed on the 13 patients presenting with relapse. Seventeen were positive and one patient, subsequently shown to have an inactive stricture, had a negative scan. Seven of the 42 newly presenting patients had abnormal scans, confirmed to be due to IBD by a combination of histology and barium examinations. Of the remaining 35 scans, three were abnormal and 32 were normal. None of these patients were subsequently proven to have IBD. These results show that in detecting active IBD, a positive WCS has a 100% sensitivity (24/24) and a 91% specificity (32/35) in the diagnosis of IBD.

CONCLUSIONS

Our results show that the WCS is very useful as an initial imaging investigation in evaluating patients with suspected IBD to select patients for further investigation.

Diagnosing sternal wound infections with 99mTc-labeled monoclonal granulocyte antibody scintigraphy

BACKGROUND

Postoperative mediastinitis is a serious complication of thoracic operations. The diagnosis can sometimes be difficult, especially in cases with subacute clinical presentation. The aim of this study was to assess the clinical use of granulocyte scintigraphy and tomography in the diagnosis of postoperative wound infection and mediastinitis.

METHODS

Twenty-nine patients after cardiothoracic operations were included, of whom 5 patients with a normal postoperative course formed the control group. We injected technetium 99m-monoclonal antigranulocyte antibodies and performed single-photon emission computed tomography after 4 and 20 hours.

RESULTS

Twenty-three patients had both the early and the later scan; the remaining 6 had only the early scan. Seven scans indicated infection: 3 cases of mediastinitis, 2 cases of superficial wound infection, 1 case of infection in a synthetic aortic graft, and 1 case of osteitis. All were verified by bacterial culture. There was one false-negative scan; this patient had only the early registration and then was explored.

CONCLUSIONS

This method when combined with the tomographic scan option is able to distinguish between deep and superficial infections. Two registrations must be made for optimal results.

Radioiodinated (aminostyryl)pyridinium (ASP) dyes: new cell membrane probes for labeling mixed leukocytes and lymphocytes for diagnostic imaging

We prepared [125I/131I]iodo-(aminostyryl)pyridinium dyes from tributylstannyl precursors. ASP 7a and 7b labeled leukocytes ex vivo (70-94%) using saline with or without washing plasma from cells. Viability of peripheral blood lymphocytes (PBLs) (dogs, rats) and splenic lymphocytes (rats) labeled with 7a and 7b (71-82%) was unchanged after labeling (> or = 88%). Canine 7b-leukocytes showed higher uptake in inflammatory lesions than did 111In-oxine leukocytes. At 3 h, aspirates contained more radioiodine than 111In (1.65:1 to 22:1) and radioiodine was cell bound. ROI measurements (3 h) gave abscess to contralateral knee ratios of 12.3 and 10.6 for 131I-7b vs. 4.8 and 2.3 for 111In-oxine.