The term “upper tract” in medicine refers to the upper urinary tract. This system continuously filters waste materials from the bloodstream to produce urine. The upper tract’s primary job is urine production, a function distinct from other parts of the urinary system responsible for storage and elimination. Understanding its components is the first step in appreciating its role in overall health.
Anatomy and Function of the Upper Urinary Tract
The upper urinary tract consists of the kidneys and the ureters. The kidneys are a pair of bean-shaped organs on either side of the spine below the rib cage. Each is protected by a fibrous membrane called the renal capsule and a layer of fat for cushioning. The right kidney sits slightly lower than the left to accommodate the liver.
Inside each kidney, about a million microscopic filtering units called nephrons perform the filtration. Each nephron contains a glomerulus, a tiny ball of blood capillaries where filtration begins. As blood flows through the glomeruli, waste, excess water, and other substances are filtered out to become urine. The kidneys also regulate blood pressure, control red blood cell production, and balance the body’s fluids and chemicals.
Once urine is produced, it travels through the ureters. These are long, narrow tubes, one connected to each kidney, that transport urine to the bladder. The walls of the ureters contain smooth muscle that contracts in waves, an action known as peristalsis. This process propels urine downward and prevents it from backing up into the kidneys.
Distinguishing the Upper and Lower Urinary Tracts
The urinary system is divided into two regions based on function. The upper tract, comprising the kidneys and ureters, is the production and transport division. Its purpose is to continuously filter blood to create urine and then move that urine away from the kidneys.
In contrast, the lower urinary tract is responsible for storage and elimination, consisting of the bladder and the urethra. The bladder is a muscular, hollow organ in the pelvis that acts as a reservoir for urine. It can expand to hold up to 500 milliliters in adults. When the bladder becomes full, nerves in its wall signal the brain, creating the urge to urinate.
The urethra is a tube extending from the bladder to the outside of the body for expelling urine. This functional separation explains why upper tract conditions often have different and more severe symptoms than those in the lower tract.
Common Conditions of the Upper Tract
Pyelonephritis is an infection of the kidney itself and is more serious than a common bladder infection (cystitis). Because the infection involves the filtration organ, symptoms are often systemic. These can include a high fever, chills, persistent pain in the flank area, nausea, and vomiting.
Kidney stones, or nephrolithiasis, are hard deposits of minerals and salts that form inside the kidneys. They may not cause symptoms until they move into the ureter. A stone traveling into the narrow ureter can cause a blockage, leading to intense pain in the side and back that radiates to the lower abdomen. Other signs include blood in the urine, pain during urination, and a persistent urge to urinate.
A blockage in a ureter can lead to hydronephrosis, the swelling of a kidney from backed-up urine. The accumulated urine puts pressure on the kidney, which can cause damage if the obstruction is not relieved. Symptoms are similar to those of kidney stones, including pain in the side or back, and may also involve changes in urinary habits and nausea.
Maintaining a Healthy Upper Tract
Adequate hydration is an important habit for upper tract health. Drinking sufficient water helps dilute waste products in the urine, which reduces the risk of kidney stone formation. Proper hydration also helps flush bacteria from the urinary system, lowering the chance of an infection reaching the kidneys.
Managing underlying health conditions also protects the upper tract. Chronic conditions like high blood pressure and diabetes can damage the small blood vessels in the kidneys over time, impairing their filtering ability. Controlling blood pressure and blood sugar levels through medication, diet, and lifestyle changes helps preserve kidney function.
Dietary choices also play a role in upper tract health. A balanced diet that is not excessively high in sodium can help manage blood pressure. For those prone to certain kidney stones, a physician may recommend specific modifications, like limiting oxalate-rich foods or animal protein, to reduce stone-forming substances in the urine.