You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

Since coronavirus disease 2019 (COVID-19) is associated with a hypercoagulable state, especially in critical patients, anticoagulation is used for thromboprophylaxis. Hemorrhagic complications, even uncommon ones such as retroperitoneal hemorrhage, can occur following anticoagulant administration. We present 5 patients with COVID-19 whose clinical course was complicated by spontaneous retroperitoneal hemorrhage. The patients were initially presented with respiratory manifestations of the infection. There was no history or evidence suggestive for traumatic injury. After hospitalization, the patients received supplemental oxygen, antibiotics, enoxaparin or heparin, interferon beta-1b (in three patients), and anticoagulation with subcutaneous injection of enoxaparin (three patients) or heparin (two patients). During the course of hospitalization, the patients showed sudden-onset abdominal pain (three cases), hypotension (three cases), and an acute drop in hemoglobin level. CT scan of the abdomen and pelvis revealed retroperitoneal hemorrhage. For one patient, owing to unstable vital signs and an expanding hematoma, surgical intervention was performed. Others were managed conservatively with discontinuation of anticoagulants, intravenous (IV) fluid resuscitation, and packed red blood cells transfusion. Three patients died due to worsening of the infection and respiratory failure. Retroperitoneal hemorrhage could be a potential complication in COVID-19 patients receiving anticoagulation. Careful monitoring of the vital signs and blood tests like hemoglobin level of such patients is essential.
["Case Report"]