Ultrasound guidance can be used for very large adrenal lesions and provides the advantage of real-time monitoring of the needle during biopsy; however, CT is usually the imaging guidance modality of choice for adrenal biopsy. CT clearly delineates the anatomic detail of the adrenal gland and adjacent structures. It also demonstrates the position of the biopsy needle within the lesion and can be used to detect procedure-related complications, such as intra-abdominal hemorrhage or pneumothorax, quickly. Non-contrast-enhanced CT is usually adequate for procedure planning and execution. Axial images acquired in 3- or 5-mm thick slices are obtained to confirm the location of the lesion and to plan needle trajectory.

Small-caliber needles (20–22 gauge) provide fine-needle aspirates for cytologic assessment, and cutting needles (18–20 gauge) provide core biopsy samples for histologic analysis. Coaxial technique using a 16–19-gauge guide needle is often used during adrenal biopsy to allow for the acquisition of both fine-needle aspirates and core biopsies. Thin-wall Chiba needles, with a beveled tip, are common guide needles. A Hawkins needle, with interchangeable blunt and sharp stylets, may be useful when the needle path lies in close proximity to major vessels or when artificial paravertebral widening with saline injection is planned.

The adrenal glands are located deep within the upper abdomen, surrounded by lung, liver, kidney, spleen, and pancreas (Fig. 16.1). The presence of these overlying structures can make adrenal gland biopsy technically challenging. Most image-guided adrenal biopsies are performed from a posterior approach. With the patient in the prone position, a direct, vertical approach to the adrenal gland is often not possible without transgressing the pleural space, which is associated with a risk of pneumothorax (Fig. 16.2). To avoid this potential complication, special techniques, such as angled approaches with or without CT gantry angulation, have been developed [22–24]. The triangulation method involves the construction of a right triangle and the use of the Pythagorean theorem and tangent ratios to calculate an extrapleural, extraperitoneal route to the lesion of interest with the patient in the prone position [23] (Fig. 16.3). The point on the skin directly overlying the lesion is marked (Z), and the depth from the skin surface to the center of the lesion is then calculated. This length (B) represents one side of the right triangle. A point on the skin surface, in the same parasagittal plane as point Z, is chosen for the needle entry site. The entry site should be below the posterior pleural reflection, either lower than the 12th rib or the transverse process of the first lumbar vertebra. The length (A) between the skin entry point and point Z represents the second side of the right triangle. The hypotenuse (C), representing the actual needle distance and an extrapleural, extraperitoneal path from the entry site to the center of the lesion, can now be calculated using the Pythagorean theorem for right triangles, (A² + B² = C²). The angle of needle insertion is determined from the tangent ratio of the two sides of the right triangle. Once the ratio is calculated, the angle can be extrapolated from a table of trigonometric ratios. It should be noted that with the angled approach, the entire needle length will not be visualized on a single transverse slice, and successive cephalad scans may be required to locate the needle tip (Fig. 16.4).

Alternatively, with the patient in the prone position, angulation of the CT gantry towards the patient’s feet to create a caudocephalad beam direction can be used to avoid the posterior costophrenic sulcus during adrenal biopsy [22, 24]. With this technique, the biopsy needle is inserted along the plane of the angled CT gantry. Beam angulation then allows for visualization of a direct path to the adrenal lesion without having to perform geometric calculations. Another advantage of this technique is that the entire path of the needle can often be seen on a single transverse slice. Beam angulation between 15° and 25° has been shown to be sufficient for most adrenal lesions.

Other authors recommend a posterior approach to the adrenal gland while the patient is in an ipsilateral decubitus position, with the side of the gland of interest down [14, 25, 26]. In the decubitus position, the dependent diaphragm is elevated, removing the risk of costophrenic sulcus transgression, and allows for a more direct approach to the adrenal gland (Fig. 16.5).

Besides the presence of interposed lung, access to the adrenal gland in the prone position may be hampered by the kidney or vertebral body (Fig. 16.6). Artificial widening of the paravertebral space using the injection of saline is a well-known technique in the biopsy of mediastinal lesions; this technique can also be applied to the biopsy of the adrenal gland [27]. Injecting saline into the posterior paravertebral space results in lateral displacement of the parietal pleura, providing an extrapleural path to the adrenal lesion (Figs. 16.7 and 16.8). When no alternative access to the adrenal gland is available, transrenal adrenal biopsy can be performed [25] (Fig. 16.9).