McDonald and McClellan classification of crossed renal ectopias

The McDonald and McClellan classification is the most commonly used classification of crossed renal ectopia. It divides them into four types based on whether there is fusion or not and whether it is unilateral or bilateral. Crossed fused renal ectopia is then further divided depending on the orientation and position of the fused kidney.

Classification

• A: crossed fused renal ectopia

  • type a: inferior ectopia

    • crossed fusion, the upper pole of the ectopic kidney fuses with the lower pole of the normal kidney

  • type b: sigmoid or S-shaped kidney

    • the hilum of the ectopic inferior kidney faces laterally and that of the normal kidney faces medially

  • type c: lump kidney

    • both kidneys fuse over a wide margin with the ureter of the ectopic kidney crossing midline

  • type d: L-shaped kidney

    • the ectopic kidney is inferior and horizontally oriented and fused with the lower pole of the normal kidney

  • type e: disc or pancake kidney

    • extensive fusion of the concave (hilar) surface of both kidneys forming a disc or doughnut-shaped mass

  • type f: superior ectoipa

    • crossed fused, the ectopic kidney is placed above the normal kidney and fused with its upper pole

• B: crossed renal ectopia without fusion

• C: solitary crossed renal ectopia

• D: bilaterally crossed renal ectopia

History and etymology

James H McDonald and Don S McClellan, American urologists, published their classification in 1957 ¹.