We reviewed patients who admitted to the ED with spontaneous , non-traumatic, renal hemorrhage, in a University Hospital and referred for imaging and we present the most characteristic imaging appearances, due to common and uncommon causes.

Clinical manifestation was acute, atypical, abdominal pain and an unexplained drop in Hemoglobin (Hb) and Hematocrit (Ht) levels.

• Angiomyolipomas (AMLs) : are a mesenchymal, bening neoplasm of the kidneys and one of the most common causes for WS. On CT, classic AMLs appear as heterogeneous masses with evidence of macroscopic fat, while on MRI, renal AMLs show high signal on T1W images and signal loss on fat-saturated sequences. Larger tumors (>4 cm) have a higher risk to spontaneous rupture. [2]
• Renal cell carcinoma (RCC) is the second most common tumor causing WS, appearing as an heterogeneous, hypervascular soft tissue mass with areas of hemorrhage and necrosis. [5,6]
• Few cases of WS in patients with anticoagulant therapy have been reported in the literature. Hemodialysis patients , due to chronic renal disease, are at an increased risk of bleeding, due to an association between uremia and platelet dysfunction. [3]
• Spontaneous rupture of simple or haemorrhagic cysts are a rare entity that can lead to WS. The size of the cyst, renal infection or calculi are predisposing factors of rupture. On CT, the ruptured, haemorrhagic cyst appears hyperdense with associated perinephric hematoma. [2]
• Renal vascular anomalies (renal aneurysms, pseudoaneurysms, fistulae or thrombosis) compromise another category of uncommon causes of WS, as well as vasculitis , such as Polyarteritis nodosa and Wegener vasculitis, in which CT and DSA are the imaging modalities of choice. [1,5,6]

Imaging goals in a suspected case of WS includes identification and characterization of renal hemorrhage, while detecting the possible cause of bleeding. However, large-volume hemorrhage at patient presentation may obscure the diagnosis of an underlying neoplasm.

US is usually the first imaging modality , in the ED to detect the perinephric / subscapular hematoma – hemorrhage , as an iso/hyper or hypoechoic fluid collection in the subscapular or the Morrison´s space, often compressing the renal parenchyma. However, US is less sensitive than CT and DSA in detecting the possible cause of renal hemorrhage.

In cases of hemodynamically unstable patients, CT is the gold standard, due to its speed and high diagnostic accuracy. CT protocol for a suspected hemorrhage includes a non-contrast CT , an arterial phase (CTA), a venous phase (CTV) and sometimes an excretory phase. The multiphasic CT illustrates the subscapular and/or perinephric hemorrhage as high-attenuation (40- 70 Hounsfield units) perirenal collections on unenhanced CT with active contrast extravasation , in cases of ongoing bleeding. Density of blood is strongly dependent on the age of the blood. Multiplanar reformations from axial CT images, such as coronal and sagittal ones, are extremely helpful to identify small renal lesions and to detect the underlying pathology of spontaneous perinephric hemorrhage. In addition, maximum intensity projection (MIP) images are extremely useful in assessing vascular causes of WS.

Super selective renovascular catheterization and embolization contributed to the control of active bleeding in unstable patients , while avoiding unnecessary emergent radical surgery. Hemodynamically stable patients were managed conservatively with a continuous monitoring of their vital signs, Ht / Hb levels and regular, imaging follow – ups. US and CT- CTA were used for follow – up evaluation.