The abdominal area is often mapped into four quadrants or nine regions to help medical professionals accurately pinpoint the origin of discomfort or pain. A sensation felt on the body’s left side, above the hip bone and extending toward the back, corresponds to the anatomical location known as the left flank or the left upper quadrant (LUQ) of the abdomen. This region houses several organs, and any physical sensation there provides an important clue about the state of these internal structures.
Anatomical Location and Primary Organs
The region on the left side above the hip is associated with the left upper quadrant (LUQ) and the left lumbar region, extending toward the flank. The flank is the soft area on the side between the last rib and the top of the hip. The two primary internal organs located here are the spleen and the left kidney.
The spleen is nestled high in the LUQ, tucked under the left rib cage, and is generally non-palpable unless enlarged. It is positioned close to the stomach and the diaphragm. The left kidney is situated lower and further back in the retroperitoneal space, behind the abdominal lining. Spanning from the lower ribs toward the hip bone, the kidney is a frequent source of sensations felt in the left flank area. The left adrenal gland sits atop the kidney. The descending colon, part of the large intestine, also runs down the left side of the abdomen. Pain originating from the stomach, the tail of the pancreas, or the splenic flexure of the colon can also be felt in this vicinity.
Functions of the Spleen and Left Kidney
The spleen and the left kidney carry out distinct processes necessary for survival. The spleen functions primarily as a blood filter and a component of the immune system, containing specialized red and white pulp tissues.
The Spleen
The red pulp filters blood, identifying and removing old or damaged red blood cells (culling). It also acts as a reservoir, holding a reserve of blood and platelets that can be released during a hemorrhage. The white pulp is packed with immune cells, including B- and T-lymphocytes. This gives the spleen an active role in fighting infections by producing antibodies and removing antibody-coated bacteria from the bloodstream.
The Left Kidney
The kidney is a filtration system that maintains the body’s internal balance. Its main function involves filtering waste products, excess salts, and water from the blood to produce urine. Beyond waste removal, the kidney regulates fluid balance and electrolyte levels, ensuring a stable chemical environment. The kidneys also produce hormones that regulate blood pressure and stimulate red blood cell production. Specialized cells release the enzyme renin to manage blood pressure, and the hormone erythropoietin signals the bone marrow to increase red blood cell production.
Common Causes of Discomfort in the Left Flank
Discomfort or pain in the left flank requires investigation, as causes range from minor issues to conditions needing immediate medical attention. Kidney issues are a frequent source of pain due to the organ’s location and function. Kidney pain is typically a dull ache that does not change with movement, unlike muscle soreness.
Kidney and Urinary Issues
The passage of a kidney stone, a hard deposit of minerals and salts, causes intense, sharp pain known as renal colic as it moves through the urinary tract. Infections, such as pyelonephritis (a bacterial infection of the kidney), also cause flank pain, often accompanied by fever, chills, or painful urination.
Digestive and Colon Issues
Because of the large intestine’s proximity, digestive problems often mimic flank pain. Severe constipation, a buildup of stool in the colon, causes cramping or aching sensations along the left side. Diverticulitis, the inflammation of small pouches in the colon lining, is a common cause of flank pain, especially in older adults. Even gas trapped in the splenic flexure of the colon can result in sharp, temporary discomfort.
Spleen and Musculoskeletal Issues
Issues involving the spleen are less common but can be serious. An enlarged spleen (splenomegaly), resulting from infections or blood disorders, may cause a feeling of fullness or discomfort in the upper left abdomen. Trauma, such as a direct blow, can lead to a ruptured spleen, which is a medical emergency due to the risk of significant internal bleeding. Musculoskeletal factors, such as a pulled muscle or strain from heavy lifting, can also cause a persistent ache that worsens with movement. Any persistent, severe, or sudden pain, especially if accompanied by fever or blood in the urine, requires prompt evaluation by a healthcare professional.