There is a version of human anatomy in which the kidneys never climb into place. Instead of settling on either side of the spine, they stay down in the pelvis and fuse into a single flat disc, roughly where the sacrum meets the abdomen. The condition is called pancake kidney, and most people who have it never find out.
A case reported by clinicians in Braga, Portugal, and published in the Indian Journal of Nephrology shows how the anomaly usually surfaces and why the reassuring version is incomplete. A three-month-old boy had an abdominal and pelvic ultrasound because he had acute gastroenteritis. The scan found no kidneys where kidneys belong. A pelvic ultrasound then showed a single discoid renal mass sitting in the midline of the pelvic cavity, 5.5 centimeters across, with normal parenchyma. MRI confirmed it.
