Despite the high perioperative risk, aggressive surgical intervention for gastrointestinal mucormycosis can help in improving prognosis. When immunocompromised patients who have undergone organ or stem cell transplantation have hematologic malignancies or diabetes mellitus or are on steroids present with an acute abdomen, we must consider the involvement of fungi, especially Mucorales, as well as bacterial causes. However, early diagnosis of gastrointestinal mucormycosis is extremely difficult, as its symptoms and imaging findings are nonspecific. In the past, the disease was often detected during autopsy; however, in recent years, it has been detected earlier more frequently [10]. Nevertheless, gastrointestinal mucormycosis is rarely diagnosed preoperatively and is most often discovered postoperatively, as in our case.

Patients prone to mucormycosis generally have a higher perioperative risk. The patient in our study also had bone marrow suppression due to a hematologic malignancy and was at risk of perioperative infection due to neutropenia and postoperative bleeding due to thrombocytopenia. The mortality rate of surgical intervention is approximately five times higher in patients with hematologic malignancies than in the general surgical population, necessitating careful consideration to determine whether surgical intervention should be performed [11]. However, surgical intervention, in addition to antifungal agents, can improve the prognosis of patients with mucormycosis [12]. Mucormycosis causes vascular invasion, thrombosis, and tissue necrosis, preventing antifungal penetration at the infection site [8, 12]. In some cases, there may be no response to antifungal drugs despite susceptibility to these agents. In such cases, prompt consideration should be given to early surgical intervention aimed at debriding the Mucor-infected site. Although it is desirable to resect as many lesions as possible to increase the efficacy of antifungals, it is difficult to determine the extent of resection. Rapid intraoperative pathology has been reported to be helpful in determining the resection margins [13] and may be useful for mucormycosis of the colon and small intestine. In our case, Mucorales was present at root of the appendix. Although there was a high possibility that Mucorales remained in the cecum, postoperative administration of antifungal agents led to the cure of the disease. Possible reasons for this are that the site of hyphae embolization due to vascular invasion was localized to the appendix and the residual lesions were well penetrated by antifungal agents. This is suggested by the absence of a contrast effect in the appendix on preoperative CT but the presence of a contrast effect in the ileum, cecum, and ascending colon.

Delayed administration of antifungal agents for mucormycosis can significantly increase mortality [14]. In immunocompromised patients presenting with an acute abdomen, antibiotics and antifungals, including L-AMB, should be administered first, with mucormycosis in consideration. If a patient does not respond to drug treatment and there is no improvement in the condition, surgical intervention should be administered promptly. If a diagnosis of mucormycosis is made, surgery should be performed immediately; however, mucormycosis is difficult to diagnose. Moreover, the criteria for considering surgical intervention in cases of undiagnosed but suspected mucormycosis have not been established. Considering the speed of mucormycosis progression, evaluation and treatment must be performed promptly if mucormycosis is suspected.

Although many studies have reported on the efficacy of surgical intervention for the rhinocerebral and pulmonary forms of mucormycosis [15,16,17], reports on surgical intervention for gastrointestinal mucormycosis are limited. However, in the present case, emergency surgery was performed within approximately 4 days of the onset of abdominal pain, which allowed for the control of inflammation, identification of the fungus, and selection of antifungals accordingly. These results suggest the effectiveness of surgical intervention in the treatment of gastrointestinal mucormycosis.