CME article 11

Imaging in Adrenal hemorrhage: Review & Protocol
Introduction US-CT-MRI  Other Investigations Conclusion References
Dr. Ashok Raghavan, Manipal Hospital, Bangalore

INTRODUCTION

Nontraumatic hemorrhage of the adrenal gland is uncommon. The causes of such hemorrhage can be classified as stress, hemorrhagic diathesis or coagulopathy, neonatal stress, underlying adrenal tumors, and idiopathic disease.

Stress
Adrenal hemorrhage is associated with stress caused by surgery, overwhelming sepsis, burns, or hypotension. Bilateral massive adrenal hemorrhage is particularly associated with a stressful critical illness, in patients who have received anticoagulant therapy. Adrenal hemorrhage is associated with fulminant meningococcemia (Waterhouse-Friderichsen syndrome), Pseudomonas infection, or infection with other gram-negative bacteria. A number of other stress-related predisposing factors have been associated with adrenal hemorrhage including pregnancy, cardiovascular disease, and administration of adrenocorticotropic hormone or steroids.

Neonatal Stress
Adrenal hemorrhage is more common in neonates than in older children or adults and is the most common adrenal mass in neonates. Such hemorrhage sometimes occurs prenatally and may be the result of a difficult labor or delivery, particularly in infants of diabetic mothers or infants who are large for their gestational age. Adrenal hemorrhage may also result from asphyxia, hypoxia, septicemia, or hemorrhagic disorders (eg, disseminated intravascular coagulopathy, hypoprothrombinemia). Neonatal adrenal hemorrhage may be discovered incidentally during US performed for other reasons. The disorder is more frequent on the right side (70% of cases), a phenomenon that has been attributed to compression of the adrenal gland between the liver and kidney.


IMAGING

US is the examination of choice in neonates with suspected adrenal hematoma. Initial US typically reveals a complex, echogenic mass. If the mass is large, the kidney may be displaced inferiorly. Regression of the mass over a period of weeks is shown on serial US scans (Fig 1 & 2).    

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Fig 1 (subacute stage)

Fig 2: Wall calcification noted


Hemorrhage of the adrenal gland occurs secondary to both traumatic conditions and nontraumatic conditions. Nontraumatic adrenal hemorrhage is uncommon and may be associated with a variety of conditions. The large majority of patients with adrenal hemorrhage do not have clinically obvious signs of adrenal insufficiency, and the diagnosis is usually made incidentally at imaging performed for another reason. Acute primary adrenal insufficiency associated with massive bilateral adrenal hemorrhage is rare but life threatening. In the critical care setting, the clinical manifestations of adrenal insufficiency are often nonspecific; coexistent disease and ongoing supportive therapy may mask its presence. Hemorrhage into an adrenal cyst or neoplasm may cause acute onset of symptoms and signs in a patient without discernible risk factors and necessitate radiologic evaluation.

The appearance of an adrenal hematoma in a patient without an underlying adrenal condition depends on the age of the patient and the age of the hematoma.

Computed Tomography
Unilateral or bilateral adrenal hematomas can be demonstrated with CT. Nontraumatic hematomas characteristically appear round or oval, an appearance similar to that of traumatic hematomas. Stranding of the periadrenal fat is evident as well. Periadrenal hemorrhage with extension to the perinephric space may be seen. The attenuation value of such a lesion depends on its age. Acute to subacute hematomas contain areas of high attenuation that usually range from 50 to 90 HU. An adrenal hematoma may calcify after 1 year. An organized chronic hematoma appears as a mass with a hypoattenuating center with or without calcifications. Such masses are termed adrenal pseudocysts (Fig 3).

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Fig 3: Chronic adrenal hematoma (adrenal pseudocyst)

Ultrasonography
US is the modality of choice for initial and follow-up evaluation of a flank mass in a neonate. In neonates, the normal adrenal glands are clearly visualized at US and consist of a hypoechoic cortex and a thin, echogenic medulla. The pattern of echogenicity of an adrenal hematoma depends again on its age. An early-stage hematoma appears solid with diffuse or inhomogeneous echogenicity. As liquefaction occurs, the mass demonstrates mixed echogenicity with a central hypoechoic region and eventually becomes completely anechoic and cystlike. Calcifications may be seen in the walls of the hematoma as early as 1–2 weeks after onset and gradually compact as the blood is absorbed. Color Doppler and power Doppler imaging allow confirmation of the avascular nature of the mass.

MR Imaging
An adrenal hematoma can be imaged and its age can be determined with MR imaging (Fig 4 & 5).

In the acute stage (less than 7 days after onset), the hematoma typically appears isointense or slightly hypointense on T1-weighted images and markedly hypointense on T2-weighted images due to a high concentration of intracellular deoxyhemoglobin, which leads to preferential T2 proton relaxation enhancement.

In the subacute stage (7 days to 7 weeks after onset), the hematoma appears hyperintense on T1- and T2-weighted images.

In the chronic stage (7 weeks after onset), a hypointense rim is present on T1- and T2-weighted images due to preferential T2 proton relaxation enhancement, which is attributed to hemosiderin deposition and the presence of a fibrous capsule. Calcifications are not evident on MR images.

MR imaging is often used to determine whether blood is the sole component of the hematoma, a finding that most likely indicates a benign cause. Such evaluation is performed with a combination of T1-weighted, T2-weighted, and gadolinium chelate–enhanced images. The blooming effect has proved useful in identifying blood and in monitoring hemorrhage as it progresses from liquid methemoglobin to hemosiderin.

 

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Fig 4

Fig 5

OTHER INVESTIGATIONS

Radiography : Suprarenal masses are rarely appreciable on plain radiographs unless curvilinear or eggshell calcifications are present. Ipsilateral atelectasis and small pleural effusions may be seen at the lung bases.

IVU: A large adrenal hematoma appears as a relatively lucent suprarenal mass; urography is helpful in distinguishing an adrenal mass from the adjacent kidney, which may be displaced inferiorly.

Angiography: Angiography is rarely used to evaluate an adrenal hematoma. Angiography can demonstrate the vascular supply of an adrenal mass and occasionally shows the contour of an adrenal cyst and hematoma or neovascularity in a tumor associated with a hematoma, but the findings are not diagnostic.

Nuclear Medicine: An adrenal hematoma typically appears as a photopenic suprarenal mass with inferior displacement of the associated kidney.

Percutaneous Needle Aspiration, Biopsy, and Drainage: In most cases, the presence of the typical imaging features of hemorrhage obviates fine-needle aspiration. CT- or US-guided percutaneous aspiration and drainage are usually indicated when an adrenal abscess is suspected.

CONCLUSION

Computed tomography (CT), ultrasonography (US), and magnetic resonance (MR) imaging play an important role in diagnosis and management. CT is the modality of choice for evaluation of adrenal hemorrhage in a patient with a history of stress or a hemorrhagic diathesis or coagulopathy (anticoagulant therapy). CT may yield the first clue to the diagnosis of adrenal insufficiency secondary to bilateral massive adrenal hemorrhage. US is the modality of choice for evaluation of neonatal hematoma, and MR imaging is helpful for further characterization. MR imaging is also useful in the diagnosis of coexistent renal vein thrombosis. When an adrenal abscess is suspected, percutaneous aspiration and drainage under imaging guidance should be performed. Hemorrhage into an adrenal cyst or tumor can cause acute onset of symptoms and signs in a patient without discernible risk factors for adrenal hemorrhage. A hemorrhagic adrenal tumor should be suspected when CT or MR imaging reveals a hemorrhagic adrenal mass of heterogeneous attenuation or signal intensity that demonstrates enhancement.

REFERENCES

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Dr. Ashok Raghavan, Manipal Hospital, Bangalore