Brian D. Saunders
Melissa M. Boltz
Presentation
A 42-year-old woman was referred for evaluation of a 2.3-cm, left, homogeneous adrenal mass discovered when a computed tomography (CT) scan was obtained on a visit to the emergency room for complaints of nausea and vomiting. During her ER visit, she was noted to have a blood pressure of 160/95. She reported a history of high blood pressure over the past year for which she had been on multiple antihypertensive medications. All laboratory data were normal at that time except for low serum potassium.
Differential Diagnosis
An adrenal incidentaloma is an asymptomatic adrenal tumor found on abdominal imaging performed for another indication. The frequency of incidentalomas is rising with the increased use of CT scanning and other imaging modalities. Currently, between 1% and 4% of all abdominal imaging studies will reveal an incidental adrenal tumor. In adults, incidental adrenal masses have a broad differential diagnosis (Table 1). Adrenal masses may be nonfunctional or functional (hormonally active), and malignant or benign. Although most incidentalomas are benign, a primary adrenocortical carcinoma is one of the most aggressive cancers, and thus this diagnosis must be considered in the differential diagnosis of any adrenal mass. Additionally, approximately 20% of incidentalomas are hormonally functional (albeit many with subclinical phenotypes), and although histologically benign, failure to diagnose and treat these patients results in avoidable morbidity.
TABLE 1. Classification of Adrenal Masses
Workup
The two major issues in managing a patient with an incidental adrenal mass are to evaluate for autonomous adrenal hormone production and to assess the malignant potential, both of which are indications for operative resection. Figure 1 depicts a suggested algorithm for the workup of incidentalomas beginning with a complete history and physical examination with specific reference to history of prior malignancies and signs and symptoms of adrenal hormone excess.
FIGURE 1 • Algorithm for the evaluation of adrenal incidentalomas.
An adrenal protocol CT scan is ideal when assessing adrenal masses. An adrenal protocol CT scan starts with a noncontrast study. The noncontrast scan is followed by the rapid injection of contrast agent, and 60 seconds later, a contrast enhanced CT scan is performed. Then, a delayed contrast (washout) scan is obtained 15 minutes after the initial contrast images. The relative percentage of contrast washout is calculated from the Hounsfield unit values of the contrast and delayed contrast CT scans. Benign adrenal cortical adenomas typically have CT attenuation values of <10 Hounsfield units on noncontrast imaging or washout >60%, which indicates a lipid-rich mass. Tumors with Hounsfield values >10 Hounsfield units are not necessarily malignant. An abdominal MRI is an increasingly utilized and acceptable imaging modality, especially in those patients with contrast allergies or reduced glomerular filtration rates. Review of imaging should account for features that would indicate malignancy, including large tumor size (>4 cm), irregular tumor margins, heterogeneity, hyperdensity, invasion into adjacent structures, lymphadenopathy, or presence of metastasis. Figure 2 shows a 2.3-cm left adrenal mass found on CT scan in this patient.
FIGURE 2 • Axial cut of a CT scan with white circle indicating a 2.3-cm diameter left adrenal mass. Radiodensity of the mass on unenhanced images shows a Hounsfield unit of 0.
Regardless of radiographic appearance, all patients with an incidental adrenal mass should undergo biochemical testing to determine functional status. A comprehensive screening panel should include serum potassium, plasma aldosterone concentration, plasma renin activity, fasting AM cortisol, ACTH, dehydroepi-androsterone sulfate (DHEAS), and plasma-free metanephrines and normetanephrines. Other measures to assess increased cortisol include 24-hour urinary-free cortisol and measurements of salivary cortisol. Urinary catecholamine measurements can also be used to screen for adrenal medullary hyperfunction. If the biochemical workup indicates the tumor is nonfunctional, the size of the tumor and the patient’s medical condition determine further management.
Diagnosis and Treatment
As stated in the case above, this patient had significant and uncontrolled hypertension, concomitant with decreased serum potassium. Further biochemical workup revealed an elevated plasma aldosterone with concurrent low plasma renin activity suggesting aldosteronoma. Additionally, cortisol, DHEAS, and catecholamines were normal. Therefore, adrenalectomy is indicated in this patient with a homogeneous, 2.3-cm, functional adrenal mass.
The use of laparoscopic techniques in surgery of adrenal glands has replaced the traditional open approach and is the preferred procedure for all small, benign tumors. The mortality with the laparoscopic approach is low at 0.2% 1 month after surgery. The overall morbidity rate averages 9% with a higher rate in pheochromocytoma and Cushing’s syndrome. Due to the benefits associated with laparoscopic surgery, open adrenalectomy should be reserved for tumors >8 cm, as well as tumors with obvious findings consistent with malignancy on preoperative imaging.
Prior to operative intervention, medical preparation may be indicated, based on functional status of the tumor. Preoperative control of hypertension in the patient with a pheochromocytoma is necessary. Alpha-adrenergic blockade is achieved using phenoxybenzamine for 7 to 10 days prior to the procedure. In addition, beta-adrenergic blockade is used after alpha-blockade to treat tachycardia and unopposed alpha-blockade. Patients with Cushing’s syndrome should receive stress-dose steroids due to suppression of the hypothalamic–pituitary–adrenal (HPA) axis of the contralateral adrenal gland. For patients with severe hypercortisolism, consideration can be given to administration of an adrenolytic agent, such as ketoconazole or mitotane. In this patient with an aldosteronoma, blood pressure and hypokalemia should be controlled with a competitive aldosterone antagonist such as spironolactone or eplerenone. These agents block the mineralocorticoid receptor, promote potassium retention, and reduce extracellular fluid volume controlling blood pressure.
Surgical Approach for Laparoscopic Adrenalectomy
In patients undergoing laparoscopic left adrenalectomy (Table 2), general anesthesia is induced and an orogastric tube and Foley catheter are inserted with the patient in supine position. Afterward, the patient is placed in the lateral decubitus position with the ipsilateral side up. The table is flexed to widen the angle between the costal margin and iliac wing. Laparoscopic access is obtained with the camera port placed slightly superior and to the left of the umbilicus. The other two working ports are placed two fingerbreadths inferior to the subcostal margin and triangulated with the camera port.
TABLE 2. Key Technical Steps and Potential Pitfalls to Laparoscopic Left Adrenalectomy
After laparoscopic access is obtained, attention is directed toward mobilizing the splenic flexure of the colon and dividing the lateral peritoneal attachments of the spleen and lienophrenic ligament until the fundus of the stomach is in view. The spleen is then reflected medially with mobilization of the tail of the pancreas. A plane medial to the adrenal gland and lateral to the aorta is bluntly created. Then, the inferior phrenic vessels and central adrenal vein are dissected and divided. The inferior and lateral attachments of the adrenal gland are divided to mobilize the gland out of the suprarenal fossa, exposing the capsule of the superior renal pole. The adrenal gland is then placed in a specimen retrieval bag and removed from the abdomen via the camera port site. Maintaining insufflation, the suprarenal fossa is inspected for adequate hemostasis. The ports are then removed, followed by fascial closure of the camera port site, and skin closure.
Should the patient have needed a laparoscopic right adrenalectomy (Table 3) patient setup and positioning is the same as stated above, except the camera port is now located slightly superior and to the right of the umbilicus. After laparoscopic access has been obtained, the lateral attachments of the liver to the diaphragm (triangular ligament) are divided and the right lobe of the liver is retracted medially. Then, a separate medial port is placed to accommodate a laparoscopic retractor for the liver. The peritoneum overlying the medial aspect of the adrenal gland is opened inferior to superior and a plane medial to the adrenal gland and posterolateral to the vena cava is bluntly developed. The remainder of the procedure is performed as outlined for the laparoscopic left adrenalectomy.
TABLE 3. Key Technical Steps and Potential Pitfalls to Laparoscopic Right Adrenalectomy
Sometimes, the adrenal gland is difficult to visualize due to perinephric fat, which is more common in men, obese patients, and those with small tumors. Intraoperative ultrasound may be useful in this situation to determine gland location. In addition, the gland should always be dissected with a rim of fatty tissue attached to its surface. This allows for manipulation of the gland without grasping it, which may tear the gland, causing bleeding. During laparoscopic right adrenalectomy, liver injury can easily occur during retraction causing large hematomas, which may make it impossible to proceed laparoscopically. Additionally, vena cava and other vascular injuries account for up to 7% of the complications of laparoscopic adrenalectomy, necessitating conversion to the open procedure. Consideration should also be given to the possibility of an aberrant adrenal vein, which drains into the right renal vein.
Special Intraoperative Considerations
Unexpected finding such as unusual retroperitoneal feeding vessels and tumor invasion into surrounding structures encountered at the time of laparoscopic adrenalectomy would raise the concern of a primary adrenal cancer and therefore, conversion to open adrenalectomy should be performed. Proceeding with the laparoscopic procedure would risk violating the tumor capsule. In addition, tumor manipulation during laparoscopic surgery causes aerosolization of cancer cells via the pneumoperitoneum and leads to seeding of the peritoneal cavity and port sites, which is known as the “chimney effect.”
Surgical Approach for Open Adrenalectomy
Should the patient have findings indicating the need for an open adrenalectomy, either a vertical midline incision or a subcostal incision is made. For conversion from laparoscopic to an open procedure, generally a subcostal incision is made with the patient in the lateral decubitus position. For a left adrenal mass resection via an open anterior approach, the lesser sac is entered. The splenic flexure of the colon is reflected caudad, and the spleen and tail of the pancreas are mobilized to expose the adrenal gland. The inferior phrenic vessels and central adrenal vein are dissected and divided with the remaining soft tissue attachments to complete the adrenalectomy. For adrenocortical cancers, en bloc splenectomy, distal pancreatectomy, nephrectomy, or partial diaphragmatic resection may be necessary.
An open anterior right adrenalectomy requires mobilization of the hepatic flexure of the colon with a partial Kocher maneuver to expose the infrahepatic vena cava. The right lobe of the liver is mobilized by dividing the triangular ligament and retracting it medially to expose the adrenal gland. The lateral and inferior margins of the adrenal gland are then mobilized. The central adrenal vein is divided and controlled with the remaining of the soft tissue attachments divided as well. Large or invasive tumors may require a thoracoabdominal incision to obtain suprahepatic vena caval control. If adrenalectomy is performed for a large adrenal cancer, en bloc resection of the right hepatic lobe, right kidney, or portion of the vena cava or diaphragm may be required.
Postoperative Management
Postoperatively, patients who undergo laparoscopic adrenalectomy typically require less fluid replacement than those undergoing open procedures. Incentive spirometry should be used to prevent postoperative atelectasis and pneumonia. In addition, pharmacologic deep venous thrombosis prophylaxis should be started. A regular diet should be resumed as soon as possible, and the Foley catheter may be discontinued when the patient’s hemodynamics, urinary output, and electrolytes are stable.
In patients with an aldosteronoma, potassium supplementation should be stopped postoperatively and antihypertensives weaned. Patients with a pheochromocytoma should be monitored in an ICU for signs of postoperative hypotension from vascular relaxation as well as hypoglycemia. Alpha blocking medications may be discontinued immediately, beta blockers weaned, and glycemic control initiated if necessary. Patients who underwent adrenalectomy for Cushing’s syndrome should be placed on pharmacologic doses of corticosteroid replacement with a plan to wean to physiologic doses. The HPA axis should be intermittently interrogated with a cosyntropin stimulation test. In the initial postoperative period, they should also be assessed for hypotension, decreased urine output, hyponatremia, hyperkalemia, hypoglycemia, and fever.
Case Conclusion
The patient undergoes successful laparoscopic left adrenalectomy and she is discharged on postoperative day 1. Postoperatively, her oral potassium supplement medications were discontinued immediately and antihypertensives slowly weaned over 2 months. The final pathology report showed the tumor to be a benign cortical aldosteronoma.
TAKE HOME POINTS
· Approximately 20% of adrenal incidentalomas are hormonally functional, and although histologically benign, failure to diagnose and treat these patients results in unnecessary morbidity.
· Adrenal incidentalomas, regardless of radiographic appearance, should be screened to determine their functional status.
· Laparoscopic adrenalectomy is the procedure of choice for small tumors (functional or not) without evidence of malignancy. Open adrenalectomy is indicated for masses >8 cm or obvious radiologic evidence of malignancy.
· The adrenal gland should always be dissected with a rim of fatty tissue attached to its surface so as not to tear the gland, which may cause bleeding that is difficult to control or seed tumor cells.
· Unexpected findings concerning for a primary adrenal cancer during laparoscopic adrenalectomy necessitates conversion to an open procedure.
SUGGESTED READINGS
Nieman LK. Approach to the patient with an adrenal incidentaloma. J Clin Endocrinol Metab. 2010;95(9):4106–4113.
NIH State-of-the-Science Statement on management of the clinically inapparent adrenal mass (“incidentaloma”). NIH Consens State Sci Statements. 2002;19(2):1–23.
Shen WT, Sturgeon C, Duh QY. From incidentaloma to adrenocortical carcinoma: the surgical management of adrenal tumors. J Surg Oncol. 2005;89(3):186–192.