Blebbing of apical cytoplasm of renal tubular epithelial cells Tubular cross section with round/irregular cytoplasmic protrusion, shaped like the Greek capital letter Omega (or it may be more vertically elongated Omega), pinched off from apical membrane without apparent closure of the lumen, involving over 50 percent of the tubular cells in cross section. The feature can be further classified into proximal or distal tubule. Abnormal renal tubular epithelial morphology