interrenal

from The Century Dictionary.

• Situated within the kidneys or the renal organ.
• noun One of two long, slender bodies, lying in the median line of the ureter, which replace the suprarenals in elasmobranchs.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Between the kidneys.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Between the kidneys.
• noun anatomy The interrenal body, an organ found in many fishes.