Anatomical terminology provides a precise language for describing the human body. The flank refers to a specific portion of the torso frequently referenced in medical contexts. Understanding the flank’s exact location and the structures it covers is important for general knowledge and the accurate assessment of symptoms. This area serves as a superficial landmark for several deep-lying structures, which explains its significance in medicine.
Defining the Flank Anatomically
The flank is the fleshy area located on the side of the body, situated between the lower margin of the rib cage and the upper ridge of the hip bone. This region is present bilaterally, on both the right and left sides of the body. Anatomically, it is bordered superiorly by the 12th rib and inferiorly by the iliac crest, the palpable upper edge of the pelvis.
The term “flank” is often used interchangeably with designations like the lateral lumbar region or the loin. In the nine-region division system of the abdomen, the flank corresponds to the left and right lumbar regions. It forms a transition zone between the abdominal cavity anteriorly and the dorsal (back) region posteriorly. The skin and superficial tissues here are relatively pliable, reflecting the lack of solid bone structure immediately beneath the surface.
Key Internal Structures Protected by the Flank
The flank provides a superficial shield for a complex arrangement of muscle and internal organs. The deep musculature includes the strong sheets of the abdominal oblique muscles and the quadratus lumborum muscle, which anchors the pelvis to the spine and lowest rib. These muscle layers provide flexibility for movement while offering support for the torso.
Deep to the muscular wall, the flank overlies the retroperitoneal space, the area behind the abdominal lining. The kidneys are the primary organs situated within this space, positioned on either side of the spine, usually just below the rib cage. The ureters, which carry urine from the kidneys to the bladder, also descend through this region.
The suprarenal (adrenal) glands sit atop the kidneys, making the flank a superficial landmark for their location. The protection offered by the thick muscle layers is important because these organs are not encased in bone like the heart or lungs. Injury to the flank can potentially impact these deep organs.
Clinical Importance and Common Flank Pain
The flank is a medically significant area because pain originating here often signals an issue with the underlying urinary tract. Flank pain is a common complaint that alerts clinicians to potential pathology in the kidneys or ureters. The most frequent cause of acute, severe flank pain is nephrolithiasis (kidney stones), which causes discomfort as they obstruct the flow of urine and distend the collecting system.
Another source of flank pain is pyelonephritis, a bacterial infection of the kidney, typically an upward extension of a urinary tract infection. This pain is often accompanied by systemic symptoms like fever and chills. Flank pain can also be musculoskeletal, arising from a simple muscle strain or injury to the lumbar muscles from heavy lifting or sudden twisting movements.
The flank is utilized as a surgical access point, particularly for procedures involving the kidney. Surgeons use a flank incision to approach the retroperitoneal space, offering a direct route to the kidney while avoiding the main abdominal cavity and its contents. The precise anatomical location of the flank guides the diagnosis and treatment of conditions affecting the urinary system and surrounding structures.