This article describes the theory of the formation of the vacuum phenomenon (VP), the detection of the VP, the different medical causes, the different locations of the presentation of the VP, and the differential diagnoses. In the human body, the cavitation effect is recognized on radiological studies; it is called the VP. The mechanism responsible for the formation of the VP is as follows: if an enclosed tissue space is allowed to expand as a rebound phenomenon after an external impact, the volume within the enclosed space will increase. In the setting of expanding volume, the pressure within the space will decrease. The solubility of the gas in the enclosed space will decrease as the pressure of the space decreases. Decreased solubility allows a gas to leave a solution. Clinically, the pathologies associated with the VP have been reported to mainly include the normal joint motion, degeneration of the intervertebral discs or joints, and trauma. The frequent use of CT for trauma patients and the high spatial resolution of CT images might produce the greatest number of chances to detect the VP in trauma patients. The VP is observed at locations that experience a traumatic impact; thus, an analysis of the VP may be useful for elucidating the mechanism of an injury. When the VP is located in the abdomen, it is important to include perforation of the digestive tract in the differential diagnosis. The presence of the VP in trauma patients does not itself influence the final outcome.

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A 74-year-old man was attacked by a wild boar while on his way home from his farm in the daytime in winter 2017 on the rural Izu peninsula. He did not provoke the boar; however, hunters were hunting animals in the mountains near the farm around the same time. The boar bit his left leg, and the man fell to the ground. The boar continued biting the man's left leg, and the man delivered a few kicks to the boar's face with his right leg. The boar then bit his right foot and ran away. The man was taken to a hospital, and a physical examination revealed 3 bite wounds on his left leg and right foot. The wounds were irrigated with sterilized saline and closed with sutures under local anesthesia. He received antibiotics and a tetanus toxoid booster. The next day, his wounds were found to be infected, and pus was drained from them. After these treatments, his wounds healed successfully. Animal bite wounds are frequently contaminated. Accordingly, in addition to early proper wound treatment, close observation of the wound is required for both the early detection of any signs of infection and early medical intervention, including appropriate drainage of pus and irrigation as necessary.

Objective: This study aimed to retrospectively determine which laboratory data on arrival for patients with mamushi bites was useful to predict the severity of mamushi bites.Materials and Methods: The subjects were divided into the following two groups: the mild group included subjects with mamushi bites Grades I and II, while the severe group included subjects with mamushi bites Grades III, IV, and V. The subjects’ variables were compared between the two groups.Results: There were no significant differences between the two groups regarding the levels of hematocrit, total protein, alanine aminotransferase, aspartate aminotransferase, creatinine phosphokinase, blood urea nitrogen, creatinine, and international normalized ratio of prothrombin time on arrival. Moreover, white blood cell count and platelet count on arrival in the mild group were significantly lower than those in the severe group. Furthermore, activated partial thromboplastin time on arrival was significantly higher in the mild group than in the severe group. Multivariate analysis using white blood cell count and platelet count and level of activated partial thromboplastin time revealed the following significant prognostic indicators of severity of mamushi bites: white blood cell count (Log Worth, 2.1; p<0.01) and platelet count (Log Worth, 1.6; p<0.05).Conclusion: White blood cell count and platelet count on arrival of patients with mamushi bites are considered significant prognostic indicators in determining the severity of mamushi bites.

Introduction-In 2011, our hospital on the Izu peninsula began to hold meetings to discuss how to manage patients with decompression illness (DCI) to establish a cooperative medical system. We retrospectively investigated the influence of these meetings and the changes subsequently effected. Methods-A medical chart review was retrospectively performed to investigate all cases between January 2005 and December 2017 in which the transport of patients with DCI via a physician-staffed helicopter emergency medical service (HEMS) was attempted. The patients were divided into 2 groups: the preprogram group and the postprogram group. Results-There were 63 patients in the preprogram group and 65 in the postprogram group. There were no cases in which a patient's symptoms deteriorated during transportation by the HEMS. The frequency of dispatch to the scene for direct evacuation in the postprogram group (86%) was greater than that in the preprogram group (74%), but the difference was not statistically significant (P=0.09). In the postprogram group, the duration of activities at the scene or the first aid hospital was significantly shorter in comparison to the preprogram group (P=0.01). Conclusions-This retrospective study revealed simultaneity between the introduction of the yearly meetings and a reduced duration of the HEMS staff's activity at either the scene or the first aid hospital.