The kidneys are bean-shaped organs whose primary function is the continuous filtration of blood to remove metabolic waste and excess fluid. Like many organs, the kidney has a distinct upper and lower end. These rounded ends are referred to in anatomy as the superior pole and the inferior, or lower, pole. The precise position of the lower pole is defined by specific anatomical landmarks.
General Location of the Kidneys
The kidneys are situated high within the abdominal cavity, against the muscles of the posterior wall. They lie in a space known as the retroperitoneum, meaning they are behind the lining of the abdominal cavity, anchored firmly against the back.
The kidneys generally span the area from the twelfth thoracic vertebra (T12) down to the third lumbar vertebra (L3). The right kidney is positioned slightly lower than the left due to the large size of the liver above it. The superior pole of each kidney is tucked beneath the eleventh and twelfth ribs, which offer substantial bony protection.
Precise Position of the Lower Pole
The lower pole marks the most inferior extent of the kidney, often correlating to the level of the third lumbar vertebra (L3). This segment is found in the lower back, roughly parallel to the top of the hip bone (iliac crest). The inferior pole is pointed more laterally and slightly forward compared to the superior pole, giving the organ a slight rotational tilt.
Because the lower pole extends beyond the protection of the rib cage, it is the most physically accessible portion of the organ. This makes it a significant landmark for medical professionals during physical examinations. The lower pole can sometimes be felt, or palpated, during a deep breath when the kidney descends slightly.
Clinical Relevance of the Lower Pole
The anatomical location and orientation of the lower pole have important consequences for medical intervention. The collecting system within the lower pole, known as the lower calyx, is particularly susceptible to the lodging of kidney stones. Due to gravity and the often narrow angle of the lower calyx, stones that enter this area are significantly less likely to pass spontaneously than those located higher up.
The lower pole region accounts for a considerable percentage of all kidney stone cases. Its location also makes it the most common access point for percutaneous nephrolithotomy, a minimally invasive surgical procedure. This procedure involves creating a small tract through the skin of the back to reach the kidney, and the lower pole is often chosen because it offers the clearest path.