Transvaginal pelvic ultrasonography is indicated for this patient with dermatomyositis, which may be associated with an underlying malignancy, especially in the first 2 years after diagnosis. Malignancy risk may also be higher in the presence of vasculitis (as seen in this patient) or cutaneous necrosis as well as in patients who are of older age at onset. Patients with dermatomyositis have an increased standardized incidence ratio of solid malignancies such as adenocarcinomas of the lung, cervix, ovaries, pancreas, colorectal, stomach, and bladder as well as non-Hodgkin lymphoma. Risk of ovarian cancer may be especially increased. In a population-based study, the standardized incidence ratio was 10.5 for ovarian cancer, highest among all cancers diagnosed. Therefore, obtaining a transvaginal pelvic ultrasonography to look for ovarian pathology, especially ovarian cancer, is recommended for this patient who has worsening dermatomyositis and new-onset ascites on examination.

Chest CT is helpful in diagnosing interstitial lung disease in patients with myositis and in evaluating malignancy; however, this patient has no evidence of respiratory symptoms but does have new-onset ascites, making ovarian cancer a more likely diagnosis.

Although this patient has elevated aspartate aminotransferase, it is likely of muscle origin and abnormal due to active myositis. Liver biopsy is not needed prior to obtaining other noninvasive studies for her abnormal liver chemistry tests and evaluation for ovarian cancer.

The diagnosis of advanced ovarian cancer is usually made by CT- or ultrasound-guided biopsy of a suspicious mass or cytologic examination of ascitic fluid. PET scan is likely to show abnormalities in her abdomen but will not lead to the correct diagnosis and is not cost-effective.

Thigh muscle MRI with specialized (STIR protocol) images may show evidence of actively involved muscle with myositis and support the diagnosis of dermatomyositis. However, this study is not needed in this patient who already has been diagnosed with dermatomyositis and has evidence of the classic rash, weakness, and elevated muscle enzymes.