The organ located at the bottom of the back is the kidney. The kidneys are a pair of bean-shaped organs that filter waste products from the blood and produce urine. They are located just below the ribs toward the middle of the back, on either side of the spine. The kidneys play a vital role in regulating blood pressure, electrolyte balance, and red blood cell production. When the kidneys are not functioning properly, waste products and excess fluids can build up in the body, leading to serious health complications. Understanding the anatomy and physiology of the kidneys is key to maintaining good kidney health.
Anatomy of the Kidneys
The kidneys are contained within the renal fascia, a tough outer capsule of connective tissue. Inside each kidney is the renal cortex and renal medulla:
Renal Cortex
The renal cortex is the outer portion of the kidney. It contains all of the nephrons, which are the functional units of the kidney responsible for blood filtration and urine production. Each kidney contains over 1 million nephrons. The renal cortex also contains renal corpuscles and renal tubules.
Renal Medulla
The inner portion of the kidney is called the renal medulla. It contains 8-18 renal pyramids which contain bundles of nephrons that filter blood and produce urine. The tips of the renal pyramids, called renal papillae, point toward the renal pelvis which collects urine and funnels it to the ureters.
Functions of the Kidneys
The main functions of the kidneys include:
- Filtering waste products from the blood
- Balancing electrolytes in the body
- Regulating blood pressure
- Stimulating red blood cell production
- Maintaining bone health
Let’s look at each of these key kidney functions in more detail:
Filtering Blood
One of the main jobs of the kidneys is to filter waste products and excess fluid from the blood. Blood enters the kidneys via the renal arteries and passes through a network of tiny blood vessels in the nephrons. Important substances like water, glucose, and minerals are reabsorbed back into the bloodstream while metabolic waste is filtered out. The filtered waste forms the urine that collects in the renal pelvis and flows to the bladder via the ureters.
Regulating Electrolytes
Electrolytes like sodium, potassium, calcium, magnesium, chloride, and phosphate must be maintained at proper levels in the blood for normal cellular function. The kidneys play an important role in regulating these electrolytes by either excreting excess electrolytes in the urine or reabsorbing needed electrolytes back into the bloodstream.
Maintaining Blood Pressure
Specialized cells in the kidneys release renin, an enzyme that triggers a series of chemical reactions that can raise blood pressure. The kidneys also regulate blood volume by adjusting how much water is excreted or retained by the body. These mechanisms help maintain normal blood pressure.
Stimulating Red Blood Cell Production
When the kidneys detect low oxygen levels in the blood, they secrete erythropoietin, a hormone that stimulates the production of red blood cells in the bone marrow. This helps increase oxygen delivery throughout the body.
Supporting Bone Health
The kidneys convert vitamin D into its active form, which helps the body absorb calcium from food. Calcium is essential for building and maintaining strong bones. The kidneys also balance calcium and phosphate levels in the blood to prevent mineralization defects.
Kidney Location
The kidneys are located in the posterior abdominal cavity, outside the peritoneal lining, on either side of the vertebral column. More specifically:
- They lie against the posterior abdominal wall, just above the waistline.
- The right kidney sits just below the liver, while the left kidney sits below the diaphragm.
- The kidneys are surrounded by fat for protection and insulation.
- They extend from the level of the 12th thoracic vertebra to the 3rd lumbar vertebra.
The exact location and orientation of each kidney varies slightly from person to person. Generally speaking, the left kidney sits a bit higher than the right kidney since the large liver crowds the right kidney downward. The left kidney is also typically slightly smaller than the right kidney.
Kidney Position Relative to Other Organs
Here is the kidney position relative to nearby organs:
- Posterior to the kidneys are the psoas major muscles and the diaphragm.
- The adrenal glands sit on top of each kidney.
- The liver is superior to the right kidney.
- The spleen sits laterally on the left side next to the left kidney.
- The pancreas sits just inferior to the left kidney.
- The intestines and colon border the medial and lateral aspects.
- The kidneys are anterior to the transversus abdominis muscles.
Knowing the position of the kidneys relative to other organs assists with medical diagnosis and surgical approaches.
Kidney Pain Location
Since the kidneys reside in the posterior abdominal cavity deep beneath the ribs, kidney pain is often felt in the middle to upper back, sides, or abdomen. Common areas kidney pain radiates include:
- Flank area – Pain felt on the side over the kidneys, often radiating to the front abdomen or lower back.
- Lower back – Kidney pain commonly radiates upward along the spine into the lower back.
- Abdomen – Pain may be felt in the front of the abdomen over the kidneys.
- Groin – Kidney pain can radiate down into the groin area.
Kidney pain location depends on which kidney is affected and the type of disease or injury:
Right Kidney Pain
Pain originating from the right kidney is typically felt in the:
- Right flank area
- Right lower back
- Right abdomen, especially near the navel
Left Kidney Pain
The left kidney pain pattern is commonly felt:
- On the left side flank
- Left lower back
- Left upper quadrant of the abdomen
Always see a doctor for persistent kidney pain since it can indicate an underlying medical condition needing treatment.
Protecting Kidney Health
Some tips to keep your kidneys healthy include:
- Drink plenty of fluids to stay hydrated.
- Maintain normal blood pressure and blood sugar levels.
- Eat a balanced, healthy diet low in sodium.
- Avoid overusing pain medications like ibuprofen that can harm kidneys.
- Don’t smoke or quit if you do.
- Exercise regularly.
- Get regular medical checkups to monitor kidney function.
Reporting any kidney problems early to your doctor provides the best chance for effective treatment. Some people are born with just one kidney or have higher kidney disease risk due to family history. Protecting kidney health is essential for maintaining overall wellbeing.
Kidney Disease
There are various types of kidney disease that can impair proper kidney function:
Chronic Kidney Disease (CKD)
CKD is a gradual, progressive loss of kidney function over time. Risk factors include high blood pressure, diabetes, and smoking. Early CKD has no symptoms but may later cause fatigue, swelling, and shortness of breath as kidney failure develops.
Glomerulonephritis
This group of disorders damages the tiny filtering units inside the kidneys, causing protein or blood in the urine along with fluid retention and waste buildup. It may be caused by infection, autoimmune disease, or genetics.
Polycystic Kidney Disease
PKD causes fluid-filled cysts to develop in the kidneys, enlarging the kidneys and damaging surrounding tissue and blood vessels. The inherited disease often leads to kidney failure.
Urinary Tract Infections (UTIs)
Bacteria entering the urinary tract can infect the bladder as cystitis or travel up to infect one or both kidneys (pyelonephritis). This causes abdominal pain, painful urination, and fever that requires prompt antibiotic treatment.
Nephrolithiasis
Mineral crystal deposits forming in the kidneys create stones that can obstruct urine flow. Kidney stones cause excruciating pain when passing through the urinary tract. Smaller stones may pass naturally while larger ones may require surgery.
Wilms Tumor
This rare kidney cancer mainly affects young children. Early warning signs may include swelling or a hard lump in the abdomen as the tumor grows. It is often curable with surgery and chemotherapy.
Talk to your doctor if you notice any symptoms of kidney problems so appropriate tests and treatment can be started if needed.
Kidney Function Tests
Doctors use certain tests to evaluate how well your kidneys are working:
Blood Tests
A blood test can measure levels of waste products like creatinine to estimate your glomerular filtration rate or GFR. This reveals how efficiently your kidneys are filtering. Higher than normal levels indicate reduced kidney function.
Urinalysis
Examining your urine sample under a microscope checks for protein, blood, or excess waste that could signal kidney damage. The urine may also be tested for specific chemicals and its appearance evaluated.
Imaging Tests
Your doctor may order imaging like an ultrasound, CT scan, or MRI to get a detailed view of the size, shape, and internal structure of your kidneys. This helps detect any abnormalities.
Kidney Biopsy
Removing a small sample of kidney tissue with a needle allows a pathologist to examine the tissue under a microscope. This biopsy helps diagnose specific kidney diseases.
Regular testing enables early diagnosis and treatment of kidney dysfunction before it becomes advanced or life-threatening.
Kidney Anatomy
Here is a table summarizing the key anatomical structures of the kidneys:
| Anatomical Structure | Description |
|---|---|
| Renal Cortex | Outer region of kidney containing nephrons that filter blood. |
| Renal Medulla | Inner region containing renal pyramids which collect filtered fluid. |
| Nephrons | Microscopic structures that filter blood and produce urine. |
| Renal Pelvis | Basin that collects urine from pyramids and funnels it to ureters. |
| Renal Artery | Branch of aorta that supplies kidneys with oxygenated blood. |
| Renal Vein | Drains deoxygenated blood from kidneys back to heart. |
| Ureter | Tubes that carry urine from kidneys to bladder. |
Having a solid understanding of renal anatomy aids medical students and health professionals in providing care for kidney-related conditions.
Conclusion
In summary, the kidneys are a vital pair of organs located at the rear of the abdominal cavity that filter waste from the blood while maintaining fluid and electrolyte balance. Many crucial body functions depend on healthy kidneys free of disease and injury. Anatomically, the kidneys contain over a million nephrons that produce urine after filtering blood routed to them by the renal arteries. Kidney pain most often manifests in the back and sides. Doctors use blood tests, urinalysis, imaging, and biopsies to monitor kidney health. Protecting the kidneys from damage through healthy lifestyle choices is key to preserving overall wellbeing.