Nuclear medicine in vasculitis

Polycystic Liver Disease: Pathophysiology, Diagnosis and Treatment

Polycystic liver disease (PLD) is a clinical condition characterized by the presence of more than 10 cysts in the liver. It is a rare disease Of genetic etiology that presents as an isolated disease or assoc\iated with polycystic kidney disease. Ductal plate malformation, ciliary dysfunction, and changes in cell signaling are the main factors involved in its pathogenesis. Most patients with PLD are asymptomatic, but in 2–5% of cases the disease has disabling symptoms and a significant reduction in quality of life. The diagnosis is based on family history of hepatic and/or renal polycystic disease, clinical manifestations, patient age, and polycystic liver phenotype shown on imaging examinations. PLD treatment has evolved considerably in the last decades. Somatostatin analogues hold promise in controlling disease progression, but liver transplantation remains a unique curative treatment modality.

Serial non-invasive assessment of antibody induced nephritis in mice using positron emission tomography

Mouse models of experimental anti-glomerular basement membrane (anti-GBM) nephritis provide an analytical tool for studying spontaneous lupus nephritis. The potential of Positron Emission Tomography (PET) was evaluated using 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) as a probe to monitor the progression of anti-GBM induced nephritis in a mouse model. The imaging results were compared to conventional measures of renal function and pathological changes. Serum and urinary vascular cell adhesion molecule-1 (VCAM-1) levels were used as measures of endothelial cell activation and inflammation. Following a challenge with anti-glomerular antibodies, mice exhibited peak changes in serum creatinine, proteinuria, and glomerulonephritis score at 14 days post-challenge (p.c.). In contrast, VCAM levels peaked at day 7 p.c. On dynamic PET images (0–60 min) of day 7, kidneys of the anti-GBM nephritis mice demonstrated a unique pattern of FDG uptake. Compared to the time activity curve (TAC) prior to challenge, a rightward shift was observed after the challenge. By day 10 p.c., kidney FDG uptake was lower than baseline and remained so until the study ended at 21 days p.c. During this time frame measures of renal dysfunction remained high but VCAM-1 levels declined. These changes were accompanied by an increase in kidney volume as measured by Computed Tomography (CT) and intra-abdominal fluid collection. Our results suggest that FDG-PET-CT can be used as a non-invasive imaging tool to longitudinally monitor the progression of renal disease activity in antibody mediated nephritis and the magnitude of renal FDG retention correlates better with early markers of renal inflammation than renal dysfunction.

[Imaging procedures in rheumatology: imaging in vasculitis]

In small vessel vasculitides, imaging studies aid in determining disease extent and activity, localization for biopsy, and for disease monitoring. They do not directly delineate the vasculitic lesion. Imaging studies focus on the upper and lower respiratory tract. Cranial magnetic resonance imaging (MRI) shows upper respiratory and retrobulbar granuloma in Wegener's granulomatosis. Furthermore, MRI depicts both mastoiditis and mucosal inflammation of the ear, nose, and throat. It is sensitive but not specific for the detection of cerebral vasculitis. Computed tomography (CT) reliably detects osseous facial lesions. Chest radiography in two planes remains the standard method of investigation for the lower respiratory tract. High-resolution CT aids in detecting further interstitial pathologies. Medium-sized vasculitides frequently occur with aneurysms. The classification criteria for polyarteritis nodosa involve the angiographic detection of visceral aneurysms. Patients with Kawasaki disease may develop coronary aneurysms that may be described by echocardiography or angiography according to diagnostic criteria. In large-vessel vasculitides such as temporal arteritis (giant cell arteritis) and Takayasu arteritis, MRI, MR-angiography, CT, CT-angiography, and duplex sonography delineate characteristic homogenous wall thickening with or without stenoses in the aorta and other arteries. There is a high correlation with angiography and positron emission tomography. Duplex sonography of the temporal arteries has a high sensitivity and specificity for the diagnosis. Data on temporal artery MRI in giant cell arteritis have recently been published.

Imaging studies in the diagnosis and management of vasculitis

The term vasculitis encompasses a number of distinct clinicopathologic disease entities. Final diagnosis should be supported by histologic study in most cases. However, different imaging modalities offer the potential for an early visualization of inflammatory vascular abnormalities, provide some diagnostic clues, and allow for an adequate assessment of therapeutic response. This review discusses recent advances in imaging techniques and refinements in vascular imaging methods, as well as a brief mention of research modalities that are increasingly used in studies of pathogenesis or in the assessment of disease progression.

Diagnosis of renal and hepatic cyst infections by 18-F-fluorodeoxyglucose positron emission tomography in autosomal dominant polycystic kidney disease

BACKGROUND

Infection of a renal or hepatic cyst is a serious complication of autosomal dominant polycystic kidney disease (ADPKD). Although crucial for successful management, early diagnosis is difficult, largely because of nonspecific symptoms and limitations of conventional imaging techniques. Because of an increased metabolic rate, inflammatory cells take up large amounts of glucose. 18-F-fluorodeoxyglucose (FDG), therefore, represents a promising agent for detection of cyst infections using positron emission tomography (PET).

METHODS

The authors studied the results of 7 FDG PET scans in 3 ADPKD patients suspected of renal or hepatic cyst infection. Two PET scans were performed in patient A (PET 1 and 2), one PET scan was performed in patient B (PET 3), and 4 PET scans were performed in patient C (PET 4, 5, 6 and 7).

RESULTS

FDG PET identified the infected cysts in 2 episodes of renal cyst infection (PET 2 and 3), 2 episodes of hepatic cyst infection (PET 6 and 7), and 1 episode of both renal and hepatic cyst infection (PET 1). In patient C, FDG PET was normal after 6 weeks of antibiotic treatment for hepatic cyst infection (PET 4) and again at a time when hepatic cyst infection was suspected, but eventually colchicine intoxication was diagnosed (PET 5).

CONCLUSION

In these patients, FDG PET proved very helpful in diagnosing and in excluding renal and hepatic cyst infections. It is concluded that FDG PET is a promising new imaging technique enabling early identification of renal and hepatic cyst infections in ADPKD patients.

Diagnosis of vasculitis

Vasculitis is a process that results from the inflammation of blood vessels and can occur de novo or secondary to a variety of diseases or drugs. Clinical presentation depends on the size and distribution of vessels involved. Anti-neutrophil cytoplasmic antibodies (ANCA) have been shown to have variable sensitivity in making the diagnosis of specific vasculitic syndromes, therefore histological confirmation may be necessary. Angiography is a useful tool in evaluating disease of large and medium-sized vessels that are inaccessible or potentially dangerous to biopsy. New imaging modalities are becoming more useful in diagnosing vessel wall changes, particularly in large-vessel vasculitides. In clinical practice it is not always possible to classify or apply a specific label to a patient with vasculitis, but for appropriate patient management it is important to define the extent and severity of disease and to exclude underlying secondary causes.