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ObjectiveFever of unknown origin (FUO) can be caused by many diseases, and varies depending on region and time period. Research on FUO in Japan has been limited to single medical institution or region, and no nationwide study has been conducted. We identified diseases that should be considered and useful diagnostic testing in patients with FUO.DesignA nationwide retrospective study.Setting17 hospitals affiliated with the Japanese Society of Hospital General Medicine.ParticipantsThis study included patients ≥18 years diagnosed with ‘classical fever of unknown origin’ (axillary temperature ≥38°C at least twice over a ≥3-week period without elucidation of a cause at three outpatient visits or during 3 days of hospitalisation) between January and December 2011.ResultsA total of 121 patients with FUO were enrolled. The median age was 59 years (range 19–94 years). Causative diseases were infectious disease in 28 patients (23.1%), non-infectious inflammatory disease in 37 (30.6%), malignancy in 13 (10.7%), other in 15 (12.4%) and unknown in 28 (23.1%). The median interval from fever onset to evaluation at each hospital was 28 days. The longest time required for diagnosis involved a case of familial Mediterranean fever. Tests performed included blood cultures in 86.8%, serum procalcitonin in 43.8% and positron emission tomography in 29.8% of patients.ConclusionsWith the widespread use of CT, FUO due to deep-seated abscess or solid tumour is decreasing markedly. Owing to the influence of the ageing population, polymyalgia rheumatica was the most frequent cause (9 patients). Four patients had FUO associated with HIV/AIDS, an important cause of FUO in Japan. In a relatively small number of cases, cause remained unclear. This may have been due to bias inherent in a retrospective study. This study identified diseases that should be considered in the differential diagnosis of FUO.

The present study identified inflammatory markers that should be considered in the differential diagnosis of classical FUO, providing useful information for future diagnosis.

In the present research, the influence of aggregate size on various characteristics (strength, permeability, water retention and water wicking) of small particle size porous concrete was examined. The properties of small particle size porous concrete using small size crushed stone (particle size: 0.6-1.2, 1.2-2.5 mm) were compared with those of ordinary porous concrete using ordinary size crushed stone (5-13 mm). According to the test results, compressive strength of porous concrete was not influenced to a significant degree by aggregate size, while flexural strength became higher with decreasing particle size. Also, it was shown that small particle size porous concrete is superior in water retention and wicking compared to ordinary particle size porous concrete. It should be noted, however, that permeability of small particle size porous concrete was rather low. Further, clarifying the configuration of voids in the porous concrete is essential for the quantitative discussion on the behaviors of water in porous concrete.