What is the Function of the Renal Pelvis in the Kidneys?


The renal pelvis, also known as the cup or pelvis of the kidney, is a crucial structure in the urinary system. Situated at the innermost part of the kidney, it serves several important functions related to urine formation, storage, and elimination. Understanding the role of the renal pelvis is essential in comprehending the overall functioning of the kidneys and maintaining a healthy urinary system.

The Anatomy of the Renal Pelvis

The renal pelvis is a funnel-shaped structure that connects the major calyces (cups) of the kidney to the ureter, which carries urine to the bladder for elimination. It is located in the central area of the kidney, known as the renal sinus, and is surrounded by renal cortex and renal medulla. The pelvis collects urine produced by the microscopic functional units of the kidneys, called nephrons, before it is transported to the bladder through the ureter.

The Calyces and Renal Papilla

The renal pelvis is divided into two or three major calyces, which further divide into several minor calyces. These calyces serve as cup-like structures that receive urine from the nephrons. At the apex of each minor calyx lies the renal papilla, which acts as a drainage point for urine from the nephrons into the calyces. This hierarchical arrangement is crucial in maintaining the flow of urine and preventing backflow.

Functions of the Renal Pelvis

Urine Collection and Storage

The primary function of the renal pelvis is to collect urine produced by the nephrons. Each nephron filters blood and reabsorbs necessary substances while eliminating waste products, resulting in the formation of urine. The urine then drains into the minor calyces, major calyces, and finally into the renal pelvis. The renal pelvis acts as a reservoir, temporarily storing urine before it is transported to the bladder for elimination.

Prevention of Urine Reflux

The renal pelvis plays a crucial role in preventing the backward flow of urine, known as reflux, from the bladder into the kidneys. The structure of the renal pelvis, particularly its funnel shape and positioning at the renal sinus, helps maintain a unidirectional flow of urine. Additionally, the ureter, which connects the renal pelvis to the bladder, has a valve-like mechanism preventing urine reflux.

Mechanical Protection

The renal pelvis provides mechanical protection to the delicate structures within the kidney. Situated deep within the body, the kidneys are vulnerable to trauma or external forces. The renal pelvis, along with its surrounding structures, acts as a cushion, protecting the nephrons and other vital components of the kidney from injury.

Transport of Urine

Another important function of the renal pelvis is the transport of urine from the kidneys to the bladder. Once the renal pelvis collects and stores urine, it contracts rhythmically, propelling the urine into the ureter. This peristaltic movement efficiently moves urine towards the bladder, ensuring the continuous elimination of waste from the body.

Renal System 4, Paranchyma, calyces and pelvis.

Renal Pelvis 👩🏾‍⚕️📚🩺

Common Issues and Disorders

Renal Pelvis Calculi

Renal pelvis calculi, commonly known as kidney stones, are mineral and salt deposits that form within the renal pelvis. These stones can cause severe pain and discomfort as they obstruct the flow of urine. Treatment options vary depending on the size and location of the stones and may range from conservative measures to surgical intervention.

Pyelitis and Pyelonephritis

Pyelitis refers to the inflammation of the renal pelvis, often caused by bacterial infections. If the infection spreads to involve the surrounding kidney tissue, it is referred to as pyelonephritis. Symptoms include fever, flank pain, and urinary tract symptoms. Prompt medical attention and appropriate antibiotic therapy are essential to prevent complications.

Renal Pelvic Tumors

Tumors can also develop within the renal pelvis, although they are relatively rare. Most renal pelvic tumors are malignant and require surgical intervention for treatment. Early detection and appropriate management are crucial for improving the prognosis.

Frequently Asked Questions (FAQs)

1. Can the renal pelvis function properly if there is a blockage in the ureter?

The renal pelvis cannot function optimally if there is a blockage in the ureter. The blockage prevents the normal flow of urine from the renal pelvis to the bladder, leading to urine backup and potential damage to the kidneys. Prompt medical intervention is necessary to relieve the blockage and restore proper urinary flow.

2. Is the renal pelvis prone to infections?

Yes, the renal pelvis can be susceptible to infections, particularly bacterial infections. Conditions such as pyelitis and pyelonephritis involve inflammation of the renal pelvis and are often caused by bacteria ascending from the urinary tract. Proper hygiene, adequate fluid intake, and prompt treatment of urinary tract infections can help reduce the risk of renal pelvis infections.

3. Can kidney stones form within the renal pelvis?

Yes, kidney stones can form within the renal pelvis. These stones are typically composed of mineral and salt deposits that accumulate over time. The presence of kidney stones can cause pain and obstruction in the urinary system, requiring medical intervention for removal.

4. How does the renal pelvis contribute to urine concentration?

The renal pelvis does not directly contribute to urine concentration. The concentration of urine primarily occurs in the renal tubules within the nephrons. However, the renal pelvis plays a crucial role in collecting and storing urine, allowing for the concentration process to take place efficiently. The concentrated urine is then transported to the bladder for elimination.

5. Can the renal pelvis regenerate if damaged?

The renal pelvis has limited regenerative capacity. In cases of mild injury or inflammation, the renal pelvis may heal with proper medical treatment and management of the underlying condition. However, severe damage or loss of renal pelvis tissue may require surgical intervention or other specialized treatments to restore its function.

6. Can abnormalities in the renal pelvis be detected through medical imaging?

Yes, medical imaging techniques such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) can detect abnormalities in the renal pelvis. These imaging modalities provide detailed visualization of the kidneys, including the renal pelvis, allowing healthcare professionals to identify any structural or functional abnormalities.


The renal pelvis performs several vital functions in the kidneys’ overall functioning and the urinary system. It collects, stores, and transports urine while preventing the backward flow of urine and providing mechanical protection to the delicate structures within the kidney. Understanding the role and potential issues associated with the renal pelvis is essential for maintaining a healthy urinary system and overall well-being.

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