Functions of the Renal Pelvis

The kidneys are two small bean-shaped organs, approximately the size of a fist, located just underneath the ribcage on either side of the spine. According to National Kidney Foundation, the kidneys filter up to 200 quarts of blood each day through the nephrons, thus maintaining electrolyte balance and removing some drugs, wastes and excess water from the body 1. The kidneys create urine as they filter the blood, which collects in the renal pelvis, a funnel-shaped structure. The urine then drains down the ureters to the bladder.

Recieves Water and Waste Products

The kidneys are composed of a million filtering units each, called nephrons. According to the National Kidney and Urologic Diseases Information Clearinghouse, each nephron contains a tiny capillary, the glomerulus, attached to a collecting tubule for the filtered wastes and water. The wastes and water form urine, which passes down a series of progressively larger tubules into a structure called a calyx. All the calices together form the funnel-shaped renal pelvis, which first receives the urine which has been filtered through the nephrons and passed down the tubules.

Collection of Urine

After the urine moves down through the series of tubules, it is collected within the renal pelvis. Before reaching the renal pelvis, some water and essential electrolytes, such as:

  • sodium
  • potassium
  • calcium
  • chloride
  • magnesium
  • phosphorus are reabsorbed back into the body

It is essential for the body to maintain an exact balance of electrolytes in order to function properly. The rest of the wastes, including proteins from tissue and muscle breakdown, and the excess water and electrolytes contained in the urine pass down into the renal pelvis for collection. In maintaining water and electrolyte balance, along with the production of the enzyme renin, the kidneys help to regulate blood pressure.

Moves Urine Into the Ureters

The urine collects within the renal pelvis, located in the center of each kidney. From there, the urine is moved down the ureters, which attach to the renal pelvis, into the bladder, where it can sit for one to eight hours before being eliminated from the body. According to NKUDIC, the kidneys are so efficient that a 30 to 40 percent decrease in kidney function may be barely noticeable. Most of those who are born with only one kidney and those who donate one of their kidneys are able to live completely normal lives. However, serious problems can ensue when kidney function is less than 25 percent. At less than 15 percent function, dialysis or kidney transplant may be considered.