Radiological findings of renal EMH are various and heterogeneous. Ultrasounds (US), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) have shown some peculiar features that help in differential diagnosis. Ultrasounds and CT imaging represent the first filter through which it is possible to place a diagnostic suspect. EMH in kidney could manifest as parenchymal, intrapelvic or perirenal involvement [4]. The renal extramedullary hematopoiesis is described as solitary or multiple masses situated in the renal parenchyma and/or in hilar region with involvement of perinephric tissues that may also infiltrate and obstruct ureters [5](Fig 3A).

Renal appearance seems to be enlarged, however with a regular morphology, principally due to the perirenal extension, which if it’s bilateral can also mimic lymphoma [2].

At Ultrasounds (US) examination, mesonephric mass mainly appears hypoechoic, with the occasional presence of a parapelvic mass, and can’t show secure differential diagnosis with any renal neoplasm (such as myeloid sarcoma, transitional cell carcinoma and renal lymphoma). Contrast-enhanced Ultrasounds Sonography (CEUS) can be also performed to assess mass vascularization. The renal mass behaviour after contrast enhancement shows poor enhancement during the early phase (less than contiguous parenchyma) that continues to decrease in the late phase of the study [6].

On CT imaging renal EMH could have soft tissue attenuation and mild enhancement post-Contrast-Enhanced Computed Tomography (CECT) [2](Fig 1).

Chronic renal EMH lesions show iron deposition and fat degeneration that give them a heterogeneous contrast-enhanced pattern [7]. Perirenal infiltration may be present, frequently appears as bilateral masses embracing both kidneys without distortion of renal profiles, and if it is significant can cause ureteral stenosis, usually seen on late phase scan after media contrast administration. Parenchymal involvement is a rare location that usually extends to hilar or intrapelvic region and causes obstructive renal failure [6]. In addition, EMH, due to its large blood vessels component, has tendency to bleed. For this reason, Radiologists should consider the option of this pathological condition on imaging, especially if haematological pathologies occur, among other renal lesions before biopsy takes place [1].

MRI is the best imaging modality to characterize tissue and internal content of focal lesions thanks to its multiparametric and multiplanar nature and different sequences used. EMH may also manifest as active or inactive lesions. Active EMH presents poor fat and iron infiltration with higher component of hematopoietic cells. This manifest as intermediate signal intensity on T1-weighted sequences, high signal intensity on T2-weighted sequences and heterogeneous enhancement after contrast media administration. Inactive lesions manifest as iron deposition leading to increased signal intensity on out-of-phases sequences rather than in-phases sequences [7]. Macroscopic fat and iron infiltration appear hypointense on T1 and T2 sequences without significant enhancement after contrast administration [2][5](Fig 2)(Fig 3).