Dromedary hump is a prominent focal bulge on the lateral border of the left kidney caused by splenic impression, which can mimic renal neoplasm. It is similar in appearance to the hump of a dromedary camel and thus the name. It is a benign anatomic variant and exhibits the same imaging characteristics as adjacent renal cortex with normal blood flow pattern on Doppler sonography. On the other hand, malignant lesions are usually heterogenous in echogenicity (though can be perfectly isoechoic to cortex sometimes) and the blood flow tends to be prominent in the periphery of the lesion.
Following Doppler loop shows that a medullary pyramid is extending into the hump with normal blood supply around it. If it was a tumor, the pyramid wouldn’t extend into the mass and the blood flow, if you see would be ‘around the mass’ and not ‘around the pyramid’.
One more case: