What Is Meant By An Extrarenal Pelvis?

In order to better understand what an extrarenal pelvis is, or means, it would pay to step back to see what a renal pelvis is, and perhaps even go back a step further to define both renal and pelvis.

Pelvis – A Definition - When we think of the pelvis, we picture the three large bones that make up the pelvis, bones which help keep in place our abdominal organs, plus provide a home for our two hip joints. The word pelvis means a basin, and our pelvic bones do form a basin of sorts. Renal on the other hand has to do with our kidneys, two bean shaped organs that have little to do with the pelvic bones, as they are located higher up in the abdomen, just under the rib cage.

Imagine A Mushroom - If you look at an illustration of a cross-section of one of the kidneys, it somewhat resembles the cross-section of a mushroom. There is the body of the mushroom, and in the middle is the stem. In the kidney, what appears to be the part of the stem that is located inside the organ, is what is called the renal pelvis. The renal pelvis is shaped a basin. It collects urine from the body of the kidney, and funnels it into the ureter. Where the ureter connects to the renal pelvis would, in our mushroom analogy, resemble the mushroom's stem.

The renal pelvis then is a catch-basin, and as you can see, has nothing to do with the much larger and bony pelvis we are more familiar with. An extrarenal pelvis is not an additional, renal pelvis. An extrarenal pelvis is a renal pelvis that is abnormally enlarged, and often protrudes from the kidney. While this is an abnormality, it does not necessarily constitute a problem, as long as it functions properly by collecting urine and funneling it into the ureter. Extrarenal means something that is sticking out of the kidney.

Complications Are Somewhat Rare - An abnormally large renal pelvis is only likely to be the source of a problem if it somehow impedes the flow of urine from the kidney. This would be more likely if the shape of the renal pelvis were to be distorted than merely being larger than normal. A renal pelvis that is truly large and protrudes from the kidney could conceivably affect the performance of an adjacent organ, but this is highly unlikely. In fact, there does not appear to be any documented evidence that this has ever been the case. Problems associated with an abnormally large and protruding renal pelvis are most apt to be the same problems which might affect a normal renal pelvis, such as the presence of a tumor or a cyst.

An Important Distinction - A distinction needs to be made between the symptoms of an extrarenal pelvis, and extrarenal symptoms. Extrarenal symptoms have nothing to do with an enlarged or protruding renal pelvis, but instead are symptoms associated with a genetic kidney disorder known as nephronophthisis. This disorder is a common genetic cause of kidney failure in children, but fortunately is quite rare. Roughly 10% of those having this disorder experience extrarenal symptoms, which in include blindness, mental retardation, and liver problems. Symptoms associated with an enlarged or protruding renal pelvis, if present at all, are rarely of a serious nature.

Renal Cell Cancer - Renal cell cancer is the most common type of kidney cancer. It can be slow to develop, and consequently there may be no noticeable symptoms during the early stages. Symptoms, when they do occur often consist of blood in the urine, a constant back pain, fatigue, weight loss, and painful urination. As long as the cancer is localized it is generally treatable and curable. If it is regional, or has become metastatic, treatment can be more difficult and the prognosis may be less positive.

Part of the treatment often involves the use of a ureteroscope, a tube-like instrument that can be inserted through the urethra, through the bladder, through the ureter, and into the renal pelvis. Ureteroscopy could also be employed to examine an extrarenal pelvis should the abnormality be suspected of causing a particular problem, as could a CT or CAT scan. The same procedure could be used to help in the diagnosis of a disease affecting the renal pelvis.

Generally Not A Problem - In the vast majority of cases, any concerns over an abnormally large, protruding renal pelvis usually turn out to be much ado about nothing. When symptoms do occur, the cause of the symptoms usually has little to do with the size of the renal pelvis, even if the renal pelvis itself is the source of the problem. Furthermore, an extrarenal pelvis, when it does occur, almost always occurs in one kidney only. An occurrence in both kidneys is exceedingly rare.

Summary - In summary, if the renal pelvis in a kidney is abnormally large and protruding it generally means very little, since an enlarged renal pelvis, whether it protrudes or not, generally functions normally and is not a source of any problems. The only problem that might be encountered would be if the renal pelvis were distorted in such a manner that it could not perform its function of collecting urine and sending it on its way.