This is information I found. It might help.
Perirenal Hematomas
Subcapsular and perinephric hematomas result from a number of traumatic (biopsy, lithotripsy, or blunt abdominal injury) and neoplastic (renal cell carcinoma or angiomyolipoma) causes [21]. The hematomas can gain access to the anterior and posterior interfascial planes via numerous bridging perinephric septa that consist of fibrous lamellae, which traverse the perirenal space (Fig. 7A,7B,7C). Conversely, these septa may be a conduit of hemorrhage or other rapidly accumulating fluid collections that recruit the interfascial planes and from there, spread into the perinephric space [12].
From this information, I believe that you may need to know where the hemorrhage is originating from. Hope this helped.