Anatomy of the Adrenal Glands, Kidney, Ureter, and Pelvis

KRISTIN C. TURZA

SAM D. GRAHAM JR.

ADRENAL

The adrenal glands are paired and located high in the retroperitoneum, on the anterior craniomedial aspect of the kidney (Figs. 1.1, 1.2 and 1.3). Distinct in appearance from the surrounding fat and pancreas by their golden color, the adrenals each weigh approximately 4 to 5 g. Glandular weight and size may change with prolonged illness or prolonged adrenocorticotropic hormone (ACTH) stimulation. The atrophic gland is thin and pale compared to the normal or hyperplastic gland. The left gland has a semicircular or crescent shape. The right gland has an inverted pyramidal or V shape. The adrenal gland consists of the cortex and medulla and arise from mesodermal (cortex) and ectodermal (medulla) elements in the medial aspect of the coelomic cavity.

FIGURE 1.1 The anatomic relationship of the adrenal glands to the aorta and inferior vena cava. Multiple arterial vessels entering the glands indicate the rich arterial supply, while a single central adrenal vein illustrates the limited and relatively constant venous damage.

Embryology

The cortex and medulla each have a unique embryologic derivation. The coelomic mesoderm, specifically the dorsal cells of the blastema cord at the medial aspect of the mesonephric bodies, gives rise to the cortex. Of note, the ventral cells of these bodies are the origin of the interstitial cells of the testis or the theca cells of the ovary. The medulla is derived from neural crest cells, which migrate from the same primordial neural crest giving rise to the sympathetic chain. The 8-week embryo has massive adrenals, approximately the size of the kidney, and they remain enlarged and very vascular until birth. Rapid regression occurs in the adrenal size during the first month. The large adrenal size with hypervascularity may predispose to adrenal hemorrhage in the newborn as well as misdiagnosis
for Wilms tumor or neuroblastoma. The medullary tissue within the gland imparts a unique tripartite structure of the head (most medial), body, and tail (most lateral). Each adrenal gland resides within the Gerota fascia with the kidney. However, in the case of renal ectopy, the adrenal remains in its natural position.

FIGURE 1.2 An anterior view of the abdomen illustrating the anatomic relationship of the adrenal glands to the surrounding gastrointestinal tract and organs.

Ectopic adrenal tissues may develop in certain locations of the body. Although rare, they may undergo neoplastic changes or hyperplasia. Ectopic adrenal tissues in most cases consist of cortex only; rarely do they contain cortex and medulla. The embryologic relationship in the urogenital ridge predisposes to adrenal ectopy in the retroperitoneum, the testis, the spermatic cord, and the region of the celiac ganglion.

Vascular Anatomy

The arterial supply remains variable; the main sources include primarily the branches from the aorta, inferior phrenic artery, and renal artery. The multiple small-caliber arterial branches must be appreciated for hemostasis during surgery. Controlling the venous drainage, although less variable, can be challenging, especially when operating on large adrenal masses, which may obscure visualization. The right adrenal vein is short and empties directly into the inferior vena cava (IVC) in its most posterolateral aspect. Bleeding from this site can be profuse and even life-threatening if not identified and controlled immediately. The left adrenal vein comparatively is smaller than the right and exits anteroinferiorly, draining into the ipsilateral renal vein.

FIGURE 1.3

Contiguous Structures

Preventing intraoperative injury to contiguous structures rests on the surgeon having a thorough knowledge of the anatomic relationships of the adrenal gland (see Fig. 1.2). The right adrenal gland lies superior to the upper pole of the right kidney, posterolateral to the IVC. Dissection of the right adrenal gland is limited medially by the duodenum and superiorly by the right hepatic lobe. Access to the right adrenal gland is more easily obtained by entering the retroperitoneum behind the liver. The right hepatic lobe can be mobilized from the colon and diaphragm by transecting the triangular, coronary, and hepatocolic ligaments, allowing visualization of the right adrenal gland just superior to the upper pole of the right kidney. Mobilization of the duodenum is also required for easier identification of the right adrenal vein. This step is critical when resecting large pheochromocytomas because early access to the adrenal vein is essential. Using the Kocher maneuver, the duodenum can be retracted medially, enabling access to the IVC and thorough dissection of the right adrenal vein. With the right adrenal vein controlled, an avascular plane is developed laterally on the gland resulting in quick and bloodless removal. The main arterial trunks and small-caliber arteries can be easily controlled with electrocautery and/or surgical clips.

The left adrenal gland is usually more medial than the right, and it lies on the upper pole of the left kidney, just lateral to the aorta. The left adrenal gland lies in close contact with the spleen and stomach, and it is crossed on its anteroinferior surface by the body of the pancreas and splenic artery and vein.
A special technical effort must be made to prevent inadvertent injury to the tail of the pancreas and/or capsule of the spleen. Releasing the splenocolic ligament allows free mobilization of the spleen, and gentle blunt dissection allows medial mobilization of the left abdominal viscera and adequate exposure of the left adrenal gland. The left adrenal vein is usually isolated in the anteroinferior aspect of the gland, and control of this vein is usually less of a problem, with minimal blood loss (see Fig. 1.3). The lowest extent of this gland is close to the renal vessel, which remains at risk of injury during adrenalectomy.

KIDNEY

The abdominal wall is composed of three layers of muscle and fascia that are derived from the same embryonic muscle sheets as the intercostal muscles. Each muscle is invested by its own layer of deep fascia and innervated by intercostal nerves. The external oblique fibers are oriented anteriorly and inferiorly, attaching posteriorly to the iliac crest, and the anterior fibers attach to the linea alba in the midline (Fig. 1.4A). The internal oblique fibers are oriented anteriorly and superiorly (Fig. 1.4B). Posteriorly, the internal oblique fibers attach to the lower four ribs and anteriorly they attach to the linea alba. In the upper abdomen, the internal oblique fascia splits to enclose the rectus muscle, whereas inferiorly, the fascia only covers the rectus muscle anteriorly. The ilioinguinal and iliohypogastric nerves are found in the internal oblique fascia anterior to the internal oblique muscle. The transversus abdominis are horizontally oriented fibers that attach to the linea alba (Fig. 1.4C). The ribs are supported by the intercostal muscles and fascia, as well as the costovertebral (costotransverse) ligament, which must be divided if the rib is to be retracted inferiorly (Fig. 1.5).

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