The kidneys filter waste products from the blood and produce urine. This urine collects in a structure within each kidney called the renal pelvis before traveling down the ureter to the bladder. An extrarenal pelvis is an anatomical variation where this urine-collecting funnel extends beyond the kidney’s internal structure. This article clarifies the nature of an extrarenal pelvis and whether it poses a health risk.
What is an Extrarenal Pelvis?
Normally, the renal pelvis is largely situated within the central cavity of the kidney, nestled among the filtering units. It acts as a funnel, gathering urine from the kidney’s collecting ducts and directing it into the ureter, which transports it to the bladder. In contrast, an extrarenal pelvis is where a significant portion of this urine-collecting structure protrudes outside the kidney’s substance.
This anatomical difference does not alter the fundamental function of the renal pelvis, which remains the collection and drainage of urine. It is simply a variation in its positioning relative to the main kidney tissue. The size and shape of an extrarenal pelvis can vary among individuals. This configuration is considered a normal variant and is not a disease or abnormality.
Is Extrarenal Pelvis Dangerous?
For most individuals, an extrarenal pelvis is not dangerous and presents no health concerns. It is a common anatomical variation; many people have this characteristic without ever knowing it or experiencing symptoms. This benign condition often goes undetected throughout a person’s life.
An extrarenal pelvis is frequently discovered incidentally during imaging studies performed for unrelated medical reasons. For example, an ultrasound or CT scan of the abdomen for digestive issues might reveal its presence. When identified, clinicians reassure patients it is a normal finding that typically causes no problems. Its presence alone does not indicate kidney dysfunction or disease.
Potential Complications and When They Arise
While an extrarenal pelvis is typically benign, specific circumstances can lead to complications, though these are uncommon. One potential issue involves urinary obstruction, where the flow of urine from the kidney is impeded. This can occur if the extrarenal pelvis, due to its more exposed position, is compressed by an anomalous blood vessel crossing its path. Scar tissue from previous inflammation or surgery near the kidney could also constrict the pelvis, leading to an obstruction.
Obstruction can result in hydronephrosis, the swelling of the kidney due to a backup of urine. This occurs when urine cannot drain properly, causing pressure to build within the kidney. Prolonged or severe hydronephrosis can impair kidney function over time. Additionally, altered drainage dynamics in an obstructed extrarenal pelvis might increase susceptibility to urinary tract infections (UTIs) because stagnant urine provides a breeding ground for bacteria. These complications arise when the anatomical variation interferes with normal urine flow, rather than from the extrarenal pelvis itself.
Diagnosis and Monitoring
An extrarenal pelvis is most commonly diagnosed through medical imaging techniques. Ultrasound is often the initial tool used, as it provides a non-invasive way to visualize the kidneys and their internal structures. More detailed imaging, such as computed tomography (CT) scans or magnetic resonance imaging (MRI), may be employed to confirm the diagnosis and assess the exact anatomy of the renal pelvis and surrounding structures. These studies can help distinguish an extrarenal pelvis from other conditions that might cause kidney swelling.
For individuals diagnosed with an extrarenal pelvis who are asymptomatic, the typical approach involves observation rather than active treatment. Regular monitoring might be recommended, especially if there are any subtle signs of urinary flow issues or if the diagnosis is made in childhood. Further investigation or intervention, such as surgical correction, is usually only considered if symptoms develop, such as flank pain, recurrent urinary tract infections, or if imaging studies reveal significant hydronephrosis or evidence of obstruction.