adrenal glands applied anatomy and adrenalectomy

adrenal glands applied anatomy

1. Adrenal gland – applied anatomy Dr Thana Ram Patel Assistant Professor Department of General Surgery Dr SN Medical College , jodhpur

2. Adrenal / suprarenal glands paired, mustard-colored structures that are positioned superior and slightly medial to the kidneys in the retroperitoneal space They are flattened and roughly pyramidal (right) or crescent shaped (left), weighing approximately 4 g each. The adrenals are among the most highly perfused organs in the body, receiving 2000 mL /kg/min of blood, after only the kidney and thyroid.

3. embryology In most respects, the cortex and medulla can be considered two completely distinct organs that happen to colocalize during development. The two portions have disparate embryologic origins. The primordial cortex arises from the coelomic mesodermal tissue near the cephalic end of the mesonephros during the fourth to fifth week of gestation. Biosynthetic activity can be detected as early as the seventh week. Cortical cell mass dominates the fetal adrenal at 4 months of development, and steroidogenesis is maximum during the third trimester. The adrenal medulla arises from the ectodermal tissues of the embryonic neural crest. It develops in parallel with the sympathetic nervous system, beginning in the fifth to sixth week of gestation. From their original position adjacent to the neural tube, neural crest cells migrate ventrally to assume a para -aortic position near the developing adrenal cortex. There, they differentiate into chromaffin cells that make up the adrenal medulla

4. This course of embryologic development yields certain surgically relevant sequelae . Both cortical and medullary tissue can be found at extra-adrenal sites (Fig. 40.2). The range of potential sites is wider for chromaffin tissue than for cortical tissue. Pheochromocytomas may arise in extra-adrenal sites more commonly than previously believed. When they are extra-adrenal, pheochromocytomas are also termed “ paragangliomas .”

5. Anatomy relationships The right adrenal gland abuts the posterolateral surface of the retrohepatic vena cava. The right adrenal fossa is bounded by the right kidney inferolaterally , diaphragm posteriorly , and bare area of the liver anterosuperiorly . The left adrenal gland lies between the left kidney and aorta, with its inferior limb extending farther caudad toward the renal hilum than the right adrenal. The other relationships of the left adrenal gland are the diaphragm posteriorly and the tail of the pancreas and splenic hilum anteriorly . Each adrenal gland is enveloped by its proper capsule, in addition to sharing Gerota fascia with the kidneys. The adrenal capsules are immediately associated with the perirenal fat.

6. vasculature Knowledge of the macroscopic vascular anatomy of the adrenal glands is essential to proper surgical management. It is important to conceptualize that although the arterial supply is diffuse, the venous drainage of each gland is usually solitary. The arterial supply arises from three distinct vessels—superior adrenal arteries from the inferior phrenic arteries, small middle adrenal arteries from the juxtaceliac aorta, and inferior adrenal arteries from the renal arteries. Of these , the inferior is the most prominent and is commonly a single identifiable vessel. The right adrenal vein is typically as short as it is wide (0.5 cm) and drains directly into the vena cava.The left adrenal vein is approximately 2 cm long and drains into the left renal vein after joining the inferior phrenic vein. This configuration presents a surgical challenge . In up to 20% of individuals, the right adrenal vein may drain into an accessory right hepatic vein or into the vena cava, at or near the confluence of such a vein. Vigilance about this variant and others (Fig. 40.3) may reduce the likelihood of intraoperative venous hemorrhage during right adrenalectomy .

7. histopathology The cortex is approximately 2 mm thick and composes more than 80% of the mass of the gland. It is made up of three layers (Fig. 40.4). The outer zona glomerulosa is a thin layer of relatively small cells with moderately eosinophilic , lipid-poor cytoplasm. It has an undulating inner border and normally does not form a complete circumferential layer. Most of the adrenal cortex is formed by the zona fasciculata , a middle layer composed of long radial columns of large, clear, lipid-laden cells. The inner zona reticularis is made up of small nests of compact, eosinophilic cells. The adrenal medulla consists of clusters and short cords of chromaffin cells, which are large, polyhedral, and packed with basophilic secretory granules. Catecholamines within these granules yield a brown reaction when treated with chromium salts, giving the cells their name. In contrast to the cortex, the adrenal medulla is richly endowed with autonomic nerve fibers and ganglion cells. Sympathetic fibers synapse directly with the chromaffin cells, constituting an interface between the nervous and endocrine systems.

8. The microvasculature of the adrenal gland functionally unifies the cortex and medulla. The adrenal arteries arborize extensively before entering the capsule to form a subcapsular plexus. Blood flows centripetally through capillaries in the zona glomerulosa and zona fasciculata before forming a deep plexus within the zona reticularis . From there, steroid-enriched postcapillary blood enters the medulla, where cortisol drives the expression of phenylethanolamine N- methyltransferase . Phenylethanolamine N- methyltransferase is responsible for the conversion of norepinephrine to epinephrine. This microvascular arrangement is essentially a portal system between the cortex and medulla.

9. Adrenalectomy open adrenalectomy , we prefer a transabdominal approach, Laparoscopic transabdominal and posterior retroperitoneoscopic approaches.

10. adrenalectomy An open adrenalectomy is almost exclusively performed when a malignant adrenal tumour is suspected. laparoscopic or retroperitoneoscopic adrenalectomy has become the ‘gold standard’ in the resection of adrenal tumours , except for tumours with signs of malignancy. The more popular approach is the laparoscopic transperitoneal approach , which offers a better view of the adrenal region than open surgery. The lateral transabdominal technique offers a wider operative field and greater versatility, and it is well suited for larger tumors and obese patients. The advantage of the retroperitoneoscopic approach is the minimal dissection required by this extra-abdominal procedure. favor the retroperitoneoscopic approach for tumors smaller than 6 cm, for bilateral tumors, and in patients with a history of extensive prior abdominal surgery

11. open Incision approach

12. Right adrenal Open right adrenalectomy begins with complete mobilization of the right lobe of the liver, including the lateral attachments and the falciform ligament. The adrenal can be exposed by rotating the liver medially or, more commonly, retracting the inferoposterior segments cephalad using long padded retractors (liver, renal vein, Deaver , or Harrington types). The retroperitoneum is entered by performing a Kocher maneuver (Fig. 40.31), and the inferior vena cava is exposed by medial reflection of the duodenum. The plane between the adrenal gland and inferior vena cava is developed first. Vascular structures, which may be numerous in highly angiogenic tumors, are ligated sequentially. The adrenal vein is isolated, securely tied, and divided. Loss of control of the adrenal vein stump may be managed with the application of a side-biting ( Satinsky ) vascular clamp.

13. Left adrenal We prefer to use a subcostal incision, which may be extended across the midline (chevron), with or without a vertical upper midline extension, to achieve wide exposure. The left adrenal can be exposed by entering the lesser sac through the gastrocolic ligament and incising the retroperitoneum inferior to the tail of the pancreas or by rotating the spleen, pancreatic tail, and stomach anteromedially , as laparoscopic adrenalectomy . The splenic flexure of the colon is mobilized inferiorly, and the plane medial to the adrenal gland is developed. The adrenal vein is isolated, tied in continuity, and divided. The small adrenal arteries can be ligated or electrocoagulated and the specimen removed after circumferential dissection is completed.

14. Laparoscopic Lateral Transabdominal Adrenalectomy Right Adrenal Left adrenal

15. Right adrenal During right adrenalectomy , the left-hand page of the open book is made up by the kidney and adrenal tumor and the right-hand page is composed of the bare area of the liver (Fig. 40.26). To gain access to the appropriate plane, the right triangular ligament of the liver must first be completely mobilized and the liver allowed to rotate anteromedially . On the right side, the colon usually lies well inferior to the operative field.

16. When developing the space between the adrenal gland and inferior vena cava from superior to inferior, the surgeon must be mindful of adrenal vein variants. The right adrenal vein is a potentially perilous structure to manage because it is short, wide, variable, and confluent with thin-walled, large-capacitance vessels (the inferior vena cava in more than 80% of cases, followed by the renal vein and, uncommonly, the right hepatic vein) that can bleed briskly if directly injured (e.g., by the cautery ), lacerated from undue traction on adjacent structures, or sheared by clips. A significant second adrenal vein may be found in up to 10% of patients. By methodically dissecting one layer at a time and moving from superior to inferior, all potential adrenal vein variants can be encountered in a controlled fashion (Fig. 40.27).

17. The adrenal vein must be dissected out delicately, definitively ligated (usually with two clips on the patient’s side), and then divided. Loss of control of the adrenal vein stump should be avoided; should this occur, conversion to an open procedure may be necessary. A conceptual contrast between left and right adrenalectomy is that left adrenalectomy centers on identification of the correct plane of dissection and right adrenalectomy centers on the avoidance of venous bleeding. Of note, the junction of the inferior vena cava and right renal vein is frequently difficult to identify. In vivo, the transition is a gradual curve rather than the 90-degree takeoff depicted in anatomy texts. Therefore, it cannot be used as a reliable anatomic landmark for identification of the adrenal vein. After control of the vein, the remaining mobilization of the right adrenal gland is straightforward because the inferomedial limb generally does not reach as far down toward the renal hilum as on the left side.

18. Left adrenal The lateral attachments of the spleen are taken down first, with the goal of rotating the left upper quadrant viscera anteromedially . Care must be taken to avoid a capsular tear of the spleen, which may arise from undue tension on a congenital or acquired adhesive band. Splenic mobilization is continued until the greater curvature of the stomach becomes visible at its apex, at which point the spleen and tail of the pancreas are allowed to fall anteriorly with rightward tilting of the table and gentle use of the fan retractor, if necessary. It is critical to achieve the correct plane of dissection precisely during this part of the procedure because the tail of the pancreas and splenic vessels are potentially vulnerable to injury. In patients with large or inferiorly positioned tumors, the splenic flexure of the colon must be mobilized caudally by dividing the splenocolic ligament.

19. We use an open book technique, which involves developing the cleft-like plane just medial to the adrenal gland and lateral to the aorta (Fig. 40.25). The left-hand page of the book is composed of the spleen, tail of the pancreas, and greater curvature of the stomach. The right-hand page of the book is made up by the kidney and adrenal tumor. The left crus of the diaphragm is a useful landmark that leads the surgeon to the left inferior phrenic vein. As mentioned in the anatomy section of this chapter, the left inferior phrenic vein courses along the medial aspect of the left adrenal gland before joining with the left adrenal vein. By developing the cleft of the open book, moving from superior to inferior, the adrenal vein is encountered at the inferomedial aspect of the adrenal gland. The small adrenal arteries that lie within this plane can be handled with energy-based coagulation.

20. The left adrenal vein is carefully dissected out, aggressively coagulated or clipped, and divided. The inferior tip of the left adrenal gland may extend low, approaching the renal hilum within millimeters. However, because the left adrenal vein is rather long (2 cm), it is generally not necessary to expose the renal vasculature during left adrenalectomy . Many patients have a superior pole renal artery branch that approaches the inferior aspect of the left adrenal gland. Injury to this structure must be carefully avoided by keeping dissection close to the adrenal capsule while the specimen is elevated away from the medial aspect of the superior pole of the left kidney. The adrenal gland is liberated by completing dissection circumferentially and posteriorly , taking the specimen off of the superior pole of the kidney and posterior abdominal wall. These attachments are deliberately divided last because they aid in suspending the adrenal gland on the lateral-superior wall of the operative field, providing exposure of the medial vascular plane during the critical initial portion of the procedure. The tumor is placed into a resilient catchment device, morcellated , and extracted. If noncutting trocars are used, only the skin will need to be closed

21. Posterior Retroperitoneoscopic Adrenalectomy lean patients with tumors smaller than 4 cm in diameter can be managed by a novel single-access technique The retroperitoneal approach has several advantages, including avoidance of mobilization of the solid organs that is necessary with transabdominal approaches, elimination of the need for repositioning during bilateral adrenalectomy , and avoidance of anterior adhesions in patients with extensive prior abdominal surgery.

22. A prone position is used, with supports placed under the lower chest and pelvic girdle so that the abdomen is allowed to hang anteriorly Three ports are placed inferior to the twelfth rib using a direct cut-down technique for initial access. Relatively high insufflation pressures of 20 to 28 mm Hg are used and have caused no complications in regard to air emboli, hypercapnia , or clinically significant soft tissue emphysema. The working space is initially created by bluntly dissecting the retroperitoneal contents anteriorly away from the ports.

23. The upper pole of the kidney is mobilized and reflected inferiorly to expose the adrenal gland. Mobilization of the adrenal gland begins near the paraspinous muscles, at the inferomedial aspect of the gland. This is where the left adrenal vein is almost always encountered early in the procedure . On the right side, the vein is encountered slightly later as dissection proceeds superiorly . The small adrenal arteries that run within the medial vascular space are coagulated. After the superior apex of the adrenal gland is mobilized, dissection proceeds circumferentially to include the periadrenal fat.