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Findings: 3 x 3 cm triangle mass is seen on the left side, cranial to the upper pole of the left kidney, and inferior to the splenic vein and tail of pancreas. The mass is isodense with normal adrenal, with a low density in the middle. This mass initially was thought to be a tumor of the adrenal. On closer examination, the normal adrenal on the left side is seen as a separate well defined structure just inferior to this mass. The mass is an extension from the stomach, possibly a diverticulum.
Diagnosis: Normal adrenals bilaterally, with part of the stomach mimicking a left sided adrenal mass.
Discussion: Anatomy - The normal right adrenal is located above the upper pole of the right kidney, posterior to the inferior vena cava and close to the posterior segment of the right lobe of the liver. The long axis of the gland is parallel to the right crus of the diaphragm. The long axis of the gland is in an almost sagittal plane. The entire sagittal plane is usually seen in a single sagittal cut in CT or MR imaging.
The normal left adrenal is situated anteromedially to the upper pole of the left kidney, just above the left renal vein. It is posterior to the splenic vessels and at the level of the pancreatic tail. The fundus of the stomach is situated anterior and cranial to the tail of the left adrenal. The axis of the left adrenal is not parallel to the diaphragm.
On cross sections, the shape of the adrenals shows considerable variation. On transverse and coronal section, the adrenals are usually depicted as linear, inverted Y shaped structures. On the left side often, it is described as inverted V, because of the shortening of one of the limbs. Shortening of any one of the limbs can produce a variety of different configurations. Transverse sections through the adrenals show different shapes at different levels. A characteristic star shaped appearance is often called the "seagull sign". In the sagittal plane, both the right and left kidneys show a dorsal curvature.
Other anatomy mistaken for adrenals - The appearance of a mass in the adrenals can be simulated by other normal or diseased anatomy, due to their proximity. This entity is often referred to as an adrenal "pseudomass". On the right side it can be simulated by the inferior vena cava, gall bladder and tumors of the upper pole of the right kidney. On the left side, it can be simulated by a pancreatic mass, aneurysm of the splenic artery, tortuous splenic vessel or varices, accessory spleen, retroperitoneal spleen, gastric diverticulum, retroperitoneal pulmonary sequestration and a normal or abnormal upper pole of the left kidney.
Differential diagnoses - Hyperfunctioning adrenal masses are primary aldosteronism (Conn’s syndrome), Cushing’s syndrome, androgen producing tumors and pheochromocytomas. Non-hyperfunctioning adrenal masses are non-hyperfunctioning adenomas, myelolipomas, cysts, hemorrhage, neuroblastoma, lymphoma, metastases and granulomatous inflammation.
References:
Gross MD, et al in "Endocrine Imaging" by Martin P Sandler et al, 1992:271-349.
Schwartz et al. "Gastric Diverticulum Simulating an Adrenal Mass:
CT Appearance and Embryogenesis", AJR, 146:553-554.
Dunnick RN in "Radiology, Diagnosis-Imaging-Intervention"
by Taveras JM, Ferrucci JT, revised ed 1996, vol. 4, ch 82 "The adrenal gland".
Korobkin M, et al. "Adrenal Imaging"; Seminars in Ultrasound, CT, and MRI; 1995,
16(4), p317-330.
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