Papillary morphology in adult human kidneys and in baby and adult pig kidneys.

The morphology of the renal papillae was studied by inspection in a series of: (1) Hampshire/Duroc piglet kidneys; (2) Danish Landrace adult pig kidneys, and (3) kidneys obtained at necropsy from adult patients. In both man and pig two main types of papillae were found: (1) a single or 'simple' papilla which drains one renal lobe, and (2) a fused or 'compound' papilla which drains two or more renal lobes. Compound papillae were found most frequently in the Hampshire/Duroc kidneys and least frequently in the human kidneys. In all three groups compound papillae were found most frequently in the upper pole. Intrarenal backflow during retrograde pyelography in the piglet kidney at intrapelvic pressures of 30-35 mm Hg (moderate) and of 70-75 mm Hg (high) was related to the morphology of the individual papilla. Both types of papilla could be divided into an open type containing at least two round or oval orifices of the papillary ducts and a closed type with small, often slit-like orifices. At moderate intrapelvic pressure intrarenal backflow occurred mainly in the open compound papillae whereas at high intrapelvic pressure it occurred in nearly all open compound papillae and in about 50% of the open simple papillae. It is concluded that papillary morphology plays an important role in the predominant upper polar occurrence of intrarenal backflow/intrarenal reflux during micturition cystography and in the higher frequency of intrarenal backflow in the mid-zone than in the lower pole in adult human beings.