The flank area is a common anatomical reference used in medicine to describe a specific region of the torso. It serves as an important landmark for healthcare professionals because it covers internal structures. When these structures are diseased or injured, they commonly cause discomfort or pain in this location. Understanding the boundaries of the flank helps recognize when symptoms indicate an issue with the protected organs.
Defining the Flank Area
The flank is located on the side of the body, wrapping from the lateral abdomen toward the back. Anatomically, it is known as the lumbar region. This soft area is situated between the lower margin of the rib cage and the top of the hip bone (iliac crest). It forms the lateral boundary of the lower back, extending from the spine outwards.
To visualize the flank, imagine the area below the ribs and above the pelvis, on the side of the body. Clinically, the flank is divided into the right and left lumbar regions during physical assessment. Pain felt here can often be traced back to the organs housed underneath.
Essential Anatomy Beneath the Flank
The flank area protects several significant internal structures, which helps in understanding the origins of flank pain. The most prominent organs beneath the flank are the kidneys. They sit high in the abdominal cavity, against the back muscles and just below the rib cage. These organs are retroperitoneal, meaning they lie behind the lining of the abdominal cavity, with one kidney on each side of the spine.
The flank region is heavily layered with musculature that forms the core and back. This includes the oblique muscles of the abdomen and deep back muscles like the quadratus lumborum. The flank also overlies portions of the large intestine: the ascending colon on the right and the descending colon on the left. The lower ribs (typically the 11th and 12th) provide bony protection to the upper flank.
Why Flank Pain Occurs
Pain in the flank region frequently occurs because of issues affecting the structures it contains, making it a relevant symptom in medical diagnosis. One common and intensely painful cause is the presence of kidney stones (renal calculi). As these solid deposits travel from the kidney into the ureter, they cause an obstruction that leads to classic, often radiating, flank pain, known as renal colic.
Kidney infections, or pyelonephritis, also manifest with flank pain, often accompanied by fever and a burning sensation during urination. This condition develops when a urinary tract infection travels upward from the bladder to the kidney tissue, causing inflammation and tenderness. Musculoskeletal issues are another frequent cause, as the muscles in the region are prone to strain, contusion, or spasm. Heavy lifting, sudden movements, or poor posture can injure the oblique or back muscles, resulting in a dull, aching discomfort that worsens with movement.