Objective:

This evidence report on the Management of the Clinically Inapparent Adrenal Mass was requested by the Office of Medical Application and Research (OMAR) at the National Institutes of Health for a State-of-the-Science Conference. The widespread use of computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound imaging (US) has resulted in the incidental discovery of asymptomatic adrenal masses (also referred to as incidentaloma) that has created a management dilemma.

Search Strategy:

Studies for the review of the primary literature were primarily identified through searches of the English language literature published between 1966 and March 2001 in Medline, BIOSIS, and Embase.

Selection Criteria:

Adrenal incidentaloma can occur in a variety of situations and authors have used a wide range of definitions for this condition. Because incidentaloma is not a specific disease entity, we accepted all studies that used their own definitions. Articles were selected for their relevance to answering five key questions.

Data Collection and Analysis:

The literature search yielded over 5,000 independent citations. We evaluated over 600 articles and included about 200 English language articles in the evidence report. Specific inclusion criteria and methods of synthesis were developed for each of the key questions. Relevant data from each article were abstracted into evidence tables. Information from the evidence tables was synthesized into summary tables describing the findings of each study.

Main Results:

Forty-five studies provided data about the prevalence of incidentaloma or the distribution of adrenal pathologies. Thirty-two studies evaluated diagnostic tests to differentiate adrenal masses. Over 80 studies provided outcome information on adrenal surgery techniques. Thirty-two studies reported prognostic information on patients with adrenal carcinoma after surgical excision, and nine articles reported follow-up results of untreated incidentaloma. Most of these studies were retrospective and the overall methodological quality was low.

Because incidentaloma is not a disease entity, the prevalence of incidentaloma will vary with the circumstances. One study used transabdominal ultrasound for general health examination reported 11 verified adrenal masses out of 41,357 subjects (prevalence 0.027 percent). Combining individual cases from several studies, the prevalence of adenoma among incidentaloma was 41 percent, metastases 19 percent, adrenocortical carcinoma 10 percent, myelolipoma 9 percent, and pheochromocytoma 8 percent, and other mostly benign lesions comprised the remainder of the lesions. The distribution of pathology varies with the definition of incidentaloma applied.

Most of the diagnostic studies were conducted for the purpose of diagnosing adrenal malignancy. In general, unenhanced or immediate enhanced CT had fair test characteristics. Delayed enhanced CT or MRI using the mass to spleen ratio had excellent test performance. Combined unenhanced CT with MRI improved the accuracy in one study. Scintigraphy had fair to excellent sensitivity and specificity. Fine needle aspiration had good to excellent test performance; however, inconclusive biopsies were common. In one small study, DHEAS had perfect sensitivity, but poor specificity.

The clinical outcomes of various surgical adrenalectomy approaches were reassessed. Evidence suggests that laparoscopic adrenalectomy in general results in less blood loss and fewer major complications. The optimal surgical approach may depend on the size and the type of tumor.

Limited follow-up data on patients with untreated incidentaloma found most tumors remain unchanged in size, some tumors disappeared or decreased in size, and about one-sixth of the tumors increased in size but none of these were adrenocortical carcinoma.

Conclusions:

With few exceptions, the overall methodological quality of the studies we examined was low. Future studies of incidentaloma need to broadly cover diverse manifestations of this condition but individual studies should apply rigorous inclusion criteria for each of the manifestations or provide thorough descriptions and careful analyses of well-defined subgroups. Future studies should incorporate rigorous methodologies to properly assess the clinical usefulness of various diagnostic tests and follow-up strategies for adrenal incidentalomas. An international registry of patients with well-documented adrenal incidentaloma may provide the best means of collecting these data.