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polycystic kidney disease, duplication, hydronephrosis, ethanol sclerotherapy

Teaching Objectives Endometriomas and ovarian hemorrhagic cysts are common ovarian masses that may appear similar on MRI. Differentiating between them is important for clinical management. The purpose of this poster is to outline the key imaging features that can help distinguish between these two entities on MRI. This exhibit intends to be a helpful tool for radiology residents and radiologists. Review of the topic Hemorrhagic cysts usually result from hemorrhage into a corpus luteum or other functional cysts, whereas endometriomas result from endometrial tissue that grows into ovaries. Endometriomas typically appear as well-defined cystic lesions with homogeneous high signal on T1 and low signal on T2-weighted images owing to the presence of deoxyhemoglobin and methemoglobin (shading sign), which is very suggestive of an endometrioma. Finding a “T2 dark spot” sign is specific for chronic hemorrhage and is useful in diagnosing endometriomas. Endometriomas may have wall enhancement on post-contrast images. The presence of an enhancing mural nodule is suggestive of malignant transformation. Ovarian hemorrhagic cysts may have variable signal intensity on both T1 and T2-weighted images due to the presence of blood products at various stages of degradation. They are usually hyperintense on T1 and T2- weighted images and do not show loss of signal on T1 fat-suppressed sequences, which is important for differentiating it from a mature cystic teratoma of the ovary. Hemorrhagic cysts may have a thickened cyst and do not enhance on post-contrast images. Conclusion Differentiating endometriomas from ovarian hemorrhagic cysts on MRI can be challenging, but careful assessment of the lesion's features on MRI can help differentiate these entities. Proper identification of these lesions is important for appropriate clinical management.

Acute and Chronic Kidney Disease (CKD) are still important causes of morbi-mortality. Due to important limitations of laboratorial markers like microalbuminuria and serum creatinine, other techniques have been studied over the last decades. We provide a pictorial review with MR images from our institution, depicting the Diffusion-weighted imaging (DWI) features of acute kidney disease (including Acute Pyelonephritis (APN), hydronephrosis, abscesses, hematomas and sediment) and CKD. DWI assesses restriction to water molecules diffusion, as well as blood microcirculation and tubular flow, being a promising biomarker of the renal microstructure. Changes on renal perfusion, glomerular and tubular flow can thus modify both renal DWI signal and Apparent Diffusion Coefficient (ADC). APN, CKD, and obstruction typically exhibit restriction to water diffusion, with corresponding low cortical ADC values. Hematomas, abscesses and sediment also exhibit restriction and tend to appear particularly bright at high b values. In the set of acute infection, the lack of ionizing radiation makes DWI very attractive during pregnancy and childhood. Also, Diffusion Tensor Imaging (DTI), by measuring fractional anisotropy, provides an even better characterization of the renal microstructure, particularly in CKD, being able to depict alterations earlier than conventional blood biomarkers. After adequate standardization of these sequences, still under investigation, the need for biopsy and contrast administration can be obviated, highlighting DWI not only as a diagnostic tool but also as way to follow-up and guide treatment decisions. The importance of DWI goes well beyond tumor detection, particularly in the kidney. It is an increasingly recognized biomarker of renal function and fibrosis, namely in CKD. The role of DWI in APN and obstruction has also been explored and its imaging findings should figure in the checklist of the urogenital radiologist.