Peritubular Capillaries: What to Know

Medically Reviewed by Jabeen Begum, MD on October 11, 2022
5 min read

The kidneys contain millions of microscopic blood vessels known as peritubular capillaries. These vessels recapture helpful nutrients like glucose and minerals and return them to your bloodstream for additional use. They also help the kidneys regulate bodily fluid levels by transforming extra water and waste into urine. 

Peritubular capillaries help your renal and urine systems function efficiently and smoothly. If you develop a disease that affects these systems, though, your peritubular capillaries may be damaged. 

Learn about the anatomy and function of peritubular capillaries, along with signs of common health conditions that can injure these vital blood vessels.

Peritubular capillaries are tiny blood vessels located inside your two kidneys. They work alongside nephrons (filtering units) to rid your body of excess water and waste. After passing through the peritubular capillaries and nephrons, waste is turned into urine that travels to the bladder and exits the body. 

Peritubular capillaries also help the body reabsorb nutrients that would otherwise be excreted as waste.

Interesting facts about peritubular capillaries: 

  • The peritubular capillaries are one of three distinct capillary systems in the kidneys. The other two capillary networks are the glomerular capillaries and vasa recta. 
  • The peritubular capillary beds maintain low blood pressure that allows them to easily absorb fluids and nutrients. 
  • Peritubular capillaries reclaim molecules that help your body function, like amino acids, glucose, and minerals.

Peritubular capillaries function as part of the urinary system. Major components of this system include the kidneys, urinary bladder, and urethra. 

The peritubular capillaries and other parts of the urinary system regulate the levels of bodily fluids and waste in the human body. The urinary system maintains normal fluid volumes through several processes, including: 

  • Controlling the levels of electrolytes in the blood 
  • Producing the hormone erythropoietin, which regulates red blood cell production 
  • Regulating the pH level of blood
  • Secreting excess water and unneeded substances as urine 

The kidneys and peritubular capillaries play an essential role in the urinary system by helping the body excrete fluids and waste. The filtering process involves several steps: 

  • Blood enters nephrons, a million tiny filtering units found in each kidney.
  • The peritubular capillaries move the blood through the nephrons into filters called the glomerulus. These filters trap fluid, small molecules, and waste in the tubule. Blood cells and proteins pass through the glomerulus harmlessly. 
  • The peritubular capillaries reabsorb essential minerals and nutrients, along with excess water. 
  • The remaining fluids and waste in the tubule turn into urine and leave the body. 

The kidneys filter an astonishing 150 quarts of blood daily, creating 1 or 2 quarts of urine. Thanks to the efficiency of the peritubular capillaries and other parts of the urinary system, most of the other substances contained in the filtered blood are reabsorbed into your bloodstream.

Each kidney contains millions of peritubular capillaries. 

These peritubular capillaries work closely with other structures and blood vessels in kidney nephrons to ensure that valuable nutrients are reabsorbed in the blood and that damaging waste is efficiently expelled from the body through urine.

The kidneys are also connected to or contain the:

Nephrons. These units each include a renal corpuscle and a tubule. The renal corpuscle creates a filtrate of blood plasma. The tubule receives this plasma filtrate and transforms it into urine. 

Proximal tubule. This filtering system is the first part of a tubule that captures nutrients and sends them back into the blood through the peritubular capillaries. 

Afferent arteriole. These blood vessels deliver blood to the glomerulus. 

Glomerulus. This network of capillaries filters plasma in the nephrons. Any plasma volume that escapes during this process gets captured by the peritubular capillaries and returned to the blood. 

Efferent arteriole. This vessel carries blood from the glomerulus to the peritubular capillaries or the vasa recta. 

Vasa recta. These networks of vessels return the filtered blood to the veins.

Conditions that damage the kidneys can also harm the fragile peritubular capillaries. If you experience changes in your urine, that may indicate that something is wrong with your peritubular capillaries and urinary system. 

Specific symptoms to watch out for include:  

  • Hematuria (blood in your urine) 
  • Fatigue
  • Insomnia
  • Loss of appetite 
  • More frequent urination 
  • Muscle cramps

Unfortunately, kidney diseases often have no symptoms, especially in the early stages. These serious conditions can progress to kidney failure and death, though, if left untreated. If you experience symptoms that may be related to your peritubular capillaries and kidneys, seek medical treatment immediately.

A range of conditions can harm your peritubular capillaries.

Chronic kidney disease. The kidneys gradually stop filtering waste effectively, eventually leading to severe damage and kidney failure if the condition is left untreated. Chronic kidney disease can only be managed through dialysis and other treatments, not cured. 

Hydronephrosis. Urine is trapped inside the urinary tract, causing the kidneys to swell up. This condition may be caused by an obstruction or muscular issues that cause urine to flow backward. 

Pyelonephritis. Commonly known as a kidney infection, pyelonephritis occurs when bacteria or viruses disrupt the function of the kidneys. This infection can be fatal if left untreated. 

Ureteral obstruction. Blockage can stop urine from exiting the kidneys, and the fluid may then travel back up into the kidneys. Common causes of ureteral obstruction include a bladder tumor, enlarged prostate, or kidney stones. 

Damage to your peritubular capillaries can also lead to peritubular capillary refraction. This condition causes your peritubular capillaries to filter blood less effectively. Peritubular capillary refraction occurs commonly in patients with chronic kidney disease, lupus nephritis, polycystic kidney disease, and other disorders.

You can help maintain the health of your peritubular capillaries by taking care of your kidneys and overall health. You can adopt simple strategies that will help you stay healthy, such as: 

  • Avoiding tobacco products
  • Drinking plenty of water to help your kidneys function effectively
  • Eating a healthy, balanced diet that includes ample fruits and vegetables
  • Following a weight loss program if you’re obese

A healthy lifestyle can help safeguard your peritubular capillaries and keep your urinary system running smoothly.