Fever of obscure origin. Diagnosis and treatment based on a series of sixty cases

A Rationale for the Use of F18-FDG PET/CT in Fever and Inflammation of Unknown Origin

This review focuses on the diagnostic value of hybrid F18-FDG Positron Emission Tomography/Computerized tomography (PET/CT) in fever of unknown origin (FUO) and inflammation of unknown origin (IUO). Due to the wide range of possible causes both FUO and IUO remain a clinical challenge for both patients and physicians. In addition, the aetiology of IUO shows the same variation in diseases as the FUO spectrum and probably requires the same diagnostic approach as FUO. There are numerous historically used diagnostic approaches incorporating invasive and non-invasive, and imaging techniques, all with relative high specificity but limited sensitivity. This hampers the generalization of these diagnostic approaches. However, recently published reports show that F18-FDG PET/CT in FUO and IUO has a high sensitivity and a relative non-specificity for malignancy, infection and inflammation. This makes F18-FDG PET/CT an ideal diagnostic tool to start the diagnostic process and to guide subsequent focused diagnostic approaches with higher specificity. In addition, F18-FDG PET/CT has a relative high negative predictive value. Therefore F18 FDG PET/CT should be incorporated in the routine diagnostic work-up of patients with FUO and IUO, preferably at an early stage in the diagnostic process.

Fever of unknown origin in a Mediterranean survey from a division of internal medicine: report of 91 cases during a 12-year-period (1991-2002)

Despite the availability of all advanced diagnostic tools, fever of unknown origin (FUO) remains a diagnostic challenge for physicians. The objective was to define, through a retrospective study, the categories of the diseases of Sicilian patients admitted at the Department of Clinical Medicine and Emerging Diseases, University of Palermo, Italy, for classical FUO. Using the registration system for patients admitted from 1991 to 2002, 508 charts of patients admitted because of fever were reviewed. Of these, only 91 patients fulfilled the criteria for classical FUO. The origin of FUO was diagnosed in 62 (68.1%) patients. Infection was the most common cause of FUO with 29 cases (31.8% of total of FUO), neoplasms accounted for 13 cases (14.2%), collagen vascular disease for 11 cases (12.0%), and miscellaneous for 9 cases (9.8%). Undiagnosed FUO were 29 (31.8%) and, of them, 22 cases were followed-up for 2 years. A definite diagnosis could be established only in 8 cases, 13 subjects completely recovered and 4 of them died. In the 73.4% of cases, the FUO have been the result of misleading factors in the diagnostic approaches as made by the physician. The results of our study are similar to those already reported by other authors in other populations, with infections as first, neoplasm as second, and collagen vascular diseases as third most important causes of FUO. In our study the prognosis for undiagnosed FUO cases was good, but a definite diagnosis could be established only in few cases. Therefore, further multicentric, prospective studies of good design are required.

The spectrum of diseases causing fever of unknown origin in Turkey: a multicenter study

OBJECTIVE

The purpose of this trial was to determine the spectrum of diseases with fever of unknown origin (FUO) in Turkey.

METHODS

A prospective multicenter study of 154 patients with FUO in twelve Turkish tertiary-care hospitals was conducted.

RESULTS

The mean age of the patients was 42+/-17 years (range 17-75). Fifty-three (34.4%) had infectious diseases (ID), 47 (30.5%) had non-infectious inflammatory diseases (NIID), 22 (14.3%) had malignant diseases (MD), and eight (5.2%) had miscellaneous diseases (Mi). In 24 (15.6%) of the cases, the reason for high fever could not be determined despite intensive efforts. The most common ID etiologies were tuberculosis (13.6%) and cytomegalovirus (CMV) infection (3.2%). Adult Still's disease was the most common NIID (13.6%) and hematological malignancy was the most common MD (7.8%). In patients with NIID, the mean duration of reaching a definite diagnosis (37+/-23 days) was significantly longer compared to the patients with ID (25+/-12 days) (p=0.007). In patients with MD, the mean duration of fever (51+/-35 days) was longer compared to patients with ID (37+/-38 days) (p=0.052).

CONCLUSIONS

Although infection remains the most common cause of FUO, with the highest percentage for tuberculosis, non-infectious etiologies seem to have increased when compared with previous studies.

Fever of unknown origin and cancer: a population-based study

BACKGROUND

Fever of unknown origin is associated with cancer, but the tumour types most commonly involved and the prognostic implications of this relation have not been studied. We aimed to assess the risk of cancer and survival after hospital admission for fever of unknown origin in a nationwide Danish follow-up study.

METHODS

We linked the Danish national registry of patients and the nationwide cancer registry, and assessed cancer risk for 43,205 patients discharged for the first time from Danish hospitals after admission for fever of unknown origin during 1977-97. We compared cancer frequency with that expected on the basis of cancer incidence in the general population, and survival of patients with cancer who had had fever of unknown origin with that of controls (ie, patients with cancer matched for cancer site, age at time of cancer diagnosis, and year of cancer diagnosis).

FINDINGS

Median follow-up was 6.3 years (IQR 2.7-12.3). During the first year of follow-up, 399 cancers were diagnosed in those who had had fever of unknown origin (standardised incidence ratio 2.3 [95% CI 2.1-2.5]). These individuals had an increased risk of developing cancer--in particular haematological malignant disease; sarcoma; and cancers of the liver, brain, kidney, colon, and pancreas. After 1 year of follow-up, individuals had an increased risk of developing haematological malignant disease and cancers of the liver, brain, and kidney. A slightly higher proportion of people diagnosed with cancer within 1 year of hospital discharge after fever of unknown origin had distant metastases compared with controls (101 [34%] of 294 vs 819 [28%] of 2907; prevalence ratio 1.2 [95% CI 1.0-1.4], and had worse survival than did controls (mortality rate ratio 1.4 [95% CI 1.2-1.6]).

INTERPRETATION

Hospital admission for fever of unknown origin is a marker of occult cancer and is associated with a poor outlook.

The Utility of a Bone Marrow Biopsy in Diagnosing the Source of Fever of Unknown Origin in Patients With AIDS

A bone marrow (BM) aspiration and biopsy is often believed to be a needed diagnostic procedure in the work-up of patients with fever of unknown origin (FUO), especially in the setting of AIDS. Is it worthwhile to proceed with this invasive diagnostic method? Clinical information obtained on 104 patients in whom AIDS had been previously diagnosed and who had been admitted with a presumptive diagnosis of FUO was retrospectively analyzed. Seventy-two cases met the inclusion criteria. A BM aspiration and biopsy had a low sensitivity as a diagnostic tool even in patients who had abnormal hematologic parameters. BM biopsy was also not helpful in diagnosing non-Hodgkin lymphoma (NHL) cases in this study. Although the incidence of NHL has risen since the emergence of HIV, the predominant types of lymphoma seen in AIDS patients are intermediate/high-grade lymphomas rather than low grade, and consequently, the incidence of BM involvement is low, decreasing the sensitivity of a BM biopsy as a diagnostic tool. These observations were validated in this study. The majority of BM biopsies in this series revealed diagnostic features of infections. This observation can likely be related to the high prevalence of HIV/AIDS patients in this community and opportunistic infections associated with this disease.

Fever of unknown origin in Israel

INTRODUCTION

Fever of unknown origin (FUO) is still a diagnostic challenge for the family physician and the internist. In the last decades a few reports have emphasized a changing pattern in the prevalence of the 3 main categories of FUO: infections, malignancies and collagen diseases.

AIMS

a. to find out if the changing pattern among the main diagnoses in patients with FUO is comparable to previous reports.

MATERIAL AND METHODS

Medical files of patients that were admitted in two 450 beds rural Israeli hospitals were checked by two physicians. All files of patients with either the diagnosis of FUO, or files of patients with fever that were hospitalized for a week or longer in internal medicine departments were reviewed.

RESULTS

101 files of patients fulfilling the criteria of FUO were found. Surprisingly 54.5% of them had infectious diseases, 7.9% had malignant disease and only 2% had collagen disease.

CONCLUSIONS

a. Infectious diseases are still the leading cause of FUO among Israeli patients. b. The prevalence of infectious and malignant diseases is comparable to other studies, however the low rate of connective tissue diseases in our study is unusual. c. The rate of undiagnosed FUO was remarkably high (32.7%), although all these patients recovered during hospitalization and probably had self limited infectious (viral) disease.

Fever of unknown origin (FUO). I A. prospective multicenter study of 167 patients with FUO, using fixed epidemiologic entry criteria. The Netherlands FUO Study Group

Internal medicine wards in all 8 university hospitals in the Netherlands participated in this prospective study of fever of unknown origin (FUO) from January 1992 until January 1994 in order to update information on the spectrum of diseases causing FUO. We used fixed epidemiologic entry criteria to achieve completeness of enrollment and to avoid unintended selection bias. After entry, immunocompetent patients were included using criteria for FUO according to Petersdorf and Beeson (30). A standardized diagnostic protocol was used, and potentially diagnostic clues (PDCs) and their use in the diagnostic process were prospectively registered. Thus, the criteria of classic FUO have been adjusted to modern times: immunocompromised patients are excluded, and the time-criterion "1 week in hospital without a diagnosis" has been replaced by a quality-criterion stating that certain investigations must be performed as a minimum, and PDCs must be followed adequately for at least 1 week, without a diagnosis being reached. A total of 167 immunocompetent patients with FUO were thus retrieved, of whom 43 (25.7%) had infections, 21 (12.6%) had neoplasms, and 40 (24.0%) had noninfectious inflammatory diseases. No diagnosis was made in 50 patients (29.9%), 37 of whom recovered spontaneously. This study confirms the changing spectrum of diseases causing FUO. Indeed, as shown by another recent study, the group of patients with FUO in whom no diagnosis can be made is expanding, and mostly it concerns self-limiting or benign fevers. Others have suggested that this trend is not really occurring (29). We did not place patients with diseases of unknown origin in the "nondiagnosis" group, and indeed made presumptive diagnoses when necessary. Nevertheless, this category of undiagnosed fevers is increasing. We believe that the higher percentage of undiagnosed cases can be attributed to the greater use of advanced diagnostic techniques attendant on an increased number of self-limited illnesses in patients meeting criteria for FUO. Because of ongoing development in diagnostic techniques and the prospective influence on the spectrum of diseases causing FUO, studies should be performed regularly to update information on this subject. Because the number of outpatient evaluations for FUO is expected to increase, patients seen on an outpatient basis should be included in future studies. To avoid unwanted selection bias, fixed epidemiologic entry criteria should be used to ensure completeness of enrollment. To shorten the period of collecting data, multicentric studies can be done using standardized diagnostic protocols. In patients with recurrent fever or fever lasting longer than 6 months, the chance of reaching a diagnosis is significantly lower, and especially in this group one should exercise the greatest caution to avoid abundant and extensive diagnostic procedures. The diagnostic process in patients with FUO remains an intriguing problem in medicine. Recent microbiologic techniques may be useful as an approach to the relatively large proportion of patients in whom we now fail to make a diagnosis.

Pyrexia of undetermined origin in advanced HIV disease

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The contribution of nuclear medicine to the patient with infection

Nuclear medicine imaging of infection has two major indications: (a) the localization of a focus of infection in patients with fever of unknown origin; in this context the radio-pharmaceutical should be highly sensitive whereas specificity is not so important because subsequent biopsy or morphologically based imaging can be performed; (b) the diagnosis of an infection in patients with localized symptoms, for example after surgery, when normal anatomy is absent or when metal implants prevent computed tomography or magnetic resonance imaging. In these latter cases high sensitivity and to an even greater extent high specificity are mandatory to guide further clinical management (conservative or surgical). All radiopharmaceuticals available to date, such as technetium-99m nanocolloids, gallium-67 citrate, indium-111- and 99mTc-labelled white blood cells, 99mTc-antigranulocyte antibodies, and 99mTc-or 111In-labelled unspecific human immunoglobulin, have different biodistributions and different physical characteristics. The absence of physiological uptake in an organ and the radiation exposure of a patient are reasons to use different radiopharmaceuticals in different clinical situations, adapted to the individual circumstances of the patient.

Fever of unknown origin

The evaluation of an FUO is a significant test of all a physician's clinical skills. The ultimate goal of the physician is to reach a diagnosis and to cure the patient in the best possible situation. Despite such pressure both externally and self-imposed, a physician needs to meticulously follow the patient and logically pursue the available diagnostic tests. To "shotgun" the process, except in the most urgent situation, is to ultimately create more frustration, confusion, and despair among the physician and his patient.

Graves' disease presenting as pyrexia of unknown origin

Fever is a common clinical manifestation of inflammatory processes of the thyroid and thyroid crisis. On the other hand, fever alone as a presenting symptom of thyrotoxicosis, without other manifestations, is extremely rare. A female patient is described in whom fever persisted for two months prior to hospitalization, but without clinical symptoms or signs to lead to suspicion of thyroid disease. After exhaustive investigation it was found that the patient was suffering from hyperthyroidism. Fever disappeared gradually on antithyroid therapy, recurred when the drugs were withdrawn for a rechallenge trial, and cleared up again after renewal. Four other cases of persistent fever as a presenting symptom of hyperthyroidism were found on a review of previous publications. Thyrotoxicosis should, therefore, be included in the differential diagnosis of pyrexia of unknown origin.

Indium-111-granulocyte scintigraphy in the evaluation of patients with fever of undetermined origin

32 patients with at least 3 weeks' unexplained fever and no established diagnosis after at least one week's in-hospital evaluation underwent scintigraphy after injection of 111In-labelled granulocytes. Focal infectious processes were correctly identified in 5 patients (1 dental and 4 abdominal infections). In a patient with non-Hodgkin's lymphoma the lymphomas took up 111In-granulocytes. Intestinal activity was observed in a patient eventually diagnosed as Whipple's disease. Apart from these findings, weak and slowly appearing focal tracer accumulations of uncertain significance were seen in 4 cases. So far, no sources of infection have been identified in any of the patients outside the infectious disease group with a negative scintigram during a median follow-up period of 8 months. Our results support the suggestion that the 111In-granulocyte scintigraphy method is a sensitive method for the detection of occult infections, and it may prove useful in the evaluation of patients with protracted fever of undetermined origin.

Dental infection as the cause of pyrexia of unknown origin--two case reports

Two cases of pyrexia of unknown origin are described in which no cause was found despite exhaustive inpatient investigation until occult dental infection was detected: extraction of the teeth involved was followed by resolution of the pyrexia. Dental infection should be considered as an unusual but eminently treatable cause of pyrexia of unknown origin.

Fever of undetermined origin: not what it used to be

Eighty cases of fever of undetermined origin seen at Dallas VAMC from 1979 to 1985 were analyzed. Infectious etiology was the cause in one half, with equal numbers of localized infections or systemic infections. In contrast to older series, viral infections were frequently seen, but tuberculosis and malaria were less commonly noted. Solid tumors were the most frequently diagnosed non-infectious cause of fever. Fevers secondary to malignancy commonly responded to non-steroidal anti-inflammatory agents. Patterns of illness were helpful in defining certain diseases such as adult Still's disease and polymyalgia rheumatica. Diagnostic tests of value are discussed.

[Differential diagnosis in fever of unknown origin: significance of concomitant clinical symptoms]

Between 1978 and 1984, 169 patients were admitted to the hospital for fever of unknown origin which was repeatedly above 38.3 degrees C. After a retrospective analysis of their records the patients were divided into two groups on the basis of the following new criteria. The first group (74 patients) was described as having "monosymptomatic fever", i.e. fever without any other physical signs, whereas the second group (95 patients) had "polysymptomatic fever", i.e. fever with additional physical signs. In 56 patients (76%) of the monosymptomatic group fever had lasted longer than 3 weeks prior to admission. In 86% of these patients case history, physical examination, microbiological tests, serological tests for microorganisms and outoimune antibodies, and microscopic inspections of tissue and/or bone marrow led to a diagnosis. Malignancies, factitious fever and fever of unknown origin were found only in this group. The patients with malignancies were generally older than the rest of the patients (p less than 0.05), and eight of ten patients suffering from connective tissue diseases also had monosymptomatic fever. The incidence of infections in this group was 42% (31 cases), in contrast to 88% (84 cases) in the polysymptomatic group (p less than 0.05). Whereas the latter had significantly more bacterial infections (p less than 0.05), viral infections prevailed in the monosymptomatic group (p less than 0.05). Thus, the etiology of polysymptomatic fever distinctly differed from that of monosymptomatic fever. Since the frequency distribution of etiologies in the monosymptomatic group corresponded to that of the cases of fever of unknown origin in the literature, differentiation into monosymptomatic and polysymptomatic fever might be helpful in determining further diagnostic workup of patients with fever of unknown origin.

Fever in adults. What to do when the cause is not obvious

A fever can be trivial or serious, fleeting or protracted. When the cause is not obvious, a variety of diagnostic testing methods along with some ingenuity on the physician's part will usually be needed. Dr Hurley outlines the approach and discusses the special challenges presented when fever of obscure cause is protracted and when fever occurs in an immunocompromised patient.

Fever of unknown origin: the value of abdominal exploration

The decision to perform exploratory laparatomy in search of the cause of prolonged fever should not be made hastily. The operation is not benign, and before the patient is subjected to it, a meticulous medical evaluation should be made. A number of recently developed diagnostic techniques are invaluable aids to the physician challenged by this diagnostic dilemma.