Isolated adrenal post-traumatic haematoma: CT and MRI findings

Clinical History

A middle-aged man with history of hypertension and previous prostatectomy was involved in a motorbike accident. He was discharged from another hospital with fractured 10th right rib, absent haemoperitoneum, increased leukocyte count and creatine-phosphokinase.
Six days later, he suffered from fever and haematuria.

Imaging Findings

At our hospital, repeated ultrasound (Fig. 1) confirmed the absence of haemoperitoneum, and detected a 4x2 cm ovoid mass in the anatomic site of the right adrenal gland, which appeared isoechoic compared to the liver parenchyma. This finding of uncertain traumatic origin was further investigated using CT (Fig. 2): the well-demarcated right adrenal lesion measured 44-46 Hounsfield Units precontrast attenuation, did not enhance internally, and showed minimal peripheral and septal enhancement on multiphasic contrast-enhanced CT acquisition.
Three days later, unenhanced MRI (Fig. 3) was performed to confirm the hypothesis of adrenal haematoma and exclude pre-existing underlying tumour: the adrenal lesion showed mildly heterogeneous hyperintense T2-signal, markedly high T1 signal intensity consistent with extracellular methaemoglobin, and thin peripheral low-intensity rim, without solid-type components.
The lesion, consistent with isolated traumatic adrenal haemorrhage, persisted stable at further follow-up CT (Fig. 4) two weeks later.

Discussion

Albeit rare, traumatic adrenal injury (TAI) is increasingly recognized with the widespread use of multidetector CT in traumatized patients. Since the small-sized adrenals are deeply embedded in retroperitoneal fat, TAI requires major blunt force and occurs with variable incidence (between 0.15% and 4%) according to the severity of blunt trauma. Rarely isolated, TAIs most usually have associated injuries of the ipsilateral ribs, kidney, liver, spleen, thoraco-lumbar spine. Proposed TAI mechanisms include: a) acute increase of intra-adrenal venous pressure from compressed inferior vena cava; b) crushing between spine and surrounding organs; and c) deceleration shearing of small adrenal arterioles. Unilateral in the vast majority, TAIs affect the right gland in 77-90% of cases since the shorter right adrenal vein eases venous congestion damage [1-5].
Specific symptoms and signs of TAI are generally absent in the setting of polytrauma. Albeit it may be sonographically detected [6, 7], TAI is often missed in emergency conditions [8]. The CT hallmark (accounting for 80% of cases) is a 2-4 cm hyperattenuating (mean 52-55 Hounsfield units) round or oval haematoma which expands or distorts the adrenal gland. Less common alternative appearances include adrenal obliteration by irregular haemorrhage, peri-adrenal haemorrhage, and uniform high-attenuating adrenal swelling. Contrast extravasation from adrenal vessels is uncommon. Associated findings include peri-adrenal fat stranding, diffuse retroperitoneal blood, and compression of adrenal gland by adjacent traumatic lesions [1-4, 9].
During non-operative management, haematomas decrease in size and attenuation over time, and generally resolve without sequelae. An appealing alternative to repeated CT, MRI provides panoramicity and the possibility to avoid contrast media, without ionising radiation. Borrowing from experience with cerebral haemorrhage, MRI allows detection and characterisation of adrenal haematomas with variable signal features according to haemoglobin oxygenation. Blood is T1-hyperintense in both the early (2-7 days) and late subacute (7-14 days) phases, in the latter T2-hyperintense because of extracellular methaemoglobin. Chronicity is indicated by progressive haemosiderin hypointensity developing from the periphery [5, 10].
Another concern is the possibility of an underlying adrenal mass predisposing to bleeding after minor trauma. Coupled with functional testing for hormonally active tumours, appropriate imaging follow-up is warranted in unexplained cases of adrenal haemorrhage. MRI is particularly robust in the differentiation between haematoma and pre-existent benign or malignant lesions [1, 5, 9].
Most TAIs are managed conservatively, with transarterial embolisation reserved for enlarging haematomas. Surgery for associated thoraco-abdominal lesions is required in approximately 25% of polytraumatized patients with TAI [1-3].

Differential Diagnosis List

Final Diagnosis

Post-traumatic haematoma of the right adrenal gland.

URL:	https://www.eurorad.org/case/13820
DOI:	10.1594/EURORAD/CASE.13820
ISSN:	1563-4086