What is Pelvic Kidney?
Renal fusion anomalies are a type of kidney abnormality that was first documented in 1938 by a researcher named Wilmer. The way we categorize these abnormalities was later expanded upon in 1957 by McDonald and McClellan. They’re usually described based on different factors, such as whether the kidneys are crossed or uncrossed, and whether they are fused together or not.
There’s a particular abnormality known as a ‘pelvic kidney’, which occurs when the kidney doesn’t move upwards from the pelvis during development in the womb. Most people with a pelvic kidney usually don’t show any symptoms, but it might increase the chances of injuries, urinary tract infections, kidney stones, and other related problems. It could also complicate surgeries, such as procedures for aortic aneurysm.
Did you know that kidney abnormalities at birth are one of the most common types of birth defects, only behind heart and skeletal defects? When it comes to the different types of renal fusion anomalies, the horseshoe kidney is the most common, whereas a pancake or lump kidney is the rarest.
An ‘ectopic kidney’ refers to a kidney that is located in an unusual place in the body. Interestingly, the blood supply of an ectopic kidney can come from a range of vessels. This is because the original blood supply from when the fetus was in the womb can be maintained. The blood for the ectopic kidney might come from the iliac arteries, direct branches from the aorta, mid sacral vessels, or the hypogastric arteries. This is important information for any surgeon preparing to operate on a patient with an ectopic kidney.
Ectopic kidneys can also occur alongside other birth abnormalities. For example, in females, these could be related to issues in the pelvis, such as Mullerian agenesis or a unicornuate uterus. Ectopic kidneys can also be part of larger congenital syndromes like CHARGE syndrome, which is recognized by a series of symptoms including heart disease, slow growth, and abnormalities in the eyes and ears, or VACTERL malformations, which is a series of different birth defects affecting the spine, heart, anus, trachea, esophagus, kidney, and limbs.
What Causes Pelvic Kidney?
Your kidneys typically develop 6 to 8 weeks after conception, moving up from the pelvis to your lower back area during week 9. However, if this process doesn’t occur properly due to issues like disrupted blood supply or other factors, a kidney may end up somewhere other than its normal position, which is called an “ectopic” kidney.
The exact location of an ectopic kidney can vary widely, with most cases being in the pelvic area opposite to the normal kidney. In some rarer instances, both kidneys can end up on the same side of your spine or even outside of the pelvis or abdominal cavity, potentially even in the chest area.
There are six types of “crossed fused ectopic kidneys,” which means kidneys that aren’t just ectopic, but that are also conjoined. These kinds are:
1. “Superior ectopia,” where the ectopic kidney is attached to the upper part of a normal kidney.
2. “Inferior ectopia,” when the ectopic kidney is positioned below the normal kidney.
3. “Sigmoid,” or S-shaped kidneys.
4. “Pancake,” or lump-shaped kidneys.
5. “Disk.”
There’s also another subtype described in a 2014 study known as “Y type,” which has joined ureters – the tubes that carry urine from your kidneys to your bladder.
Ectopic kidneys usually affect one side, but there are cases where both kidneys are ectopic. This is different from a “horseshoe kidney,” where the bottom parts of both kidneys are fused and are usually within the abdominal cavity.
A particularly unusual type of ectopic kidneys is a “pancake kidney.” This condition results in kidneys that are fused along their inner sides, leading to a rounded, disc-shaped mass. Sometimes, this mass may have a hole in the centre (resembling a doughnut), or the inner side can fuse entirely. Despite this unusual formation, there are typically still two separate systems for gathering and processing urine. Pancake kidneys appear more often in males than females, and they’re most commonly detected in individuals aged between 30 to 60 years old.
Risk Factors and Frequency for Pelvic Kidney
The likelihood of babies being born with pelvic kidneys varies worldwide, but it typically happens in about 1 in 1000 births. For instance, a past study in Turkey, which reviewed 13,701 prenatal scans, discovered that 1 in every 571 pregnancies showed signs of a pelvic kidney. However, this study only involved scans with a normal amount of amniotic fluid.
In Taiwan, a different study screened 132,000 school children and found only 1 in every 5000 had pelvic kidneys. This result may be an underestimate due to the method used for screening.
It is most probable to find an ectopic, or displaced, pelvic kidney in a fetus if an ultrasound during pregnancy does not show a kidney where it should be, but there is a normal amount of amniotic fluid.
Signs and Symptoms of Pelvic Kidney
Most cases of renal ectopy, where the kidneys are not in their usual position, are diagnosed by chance when they don’t show any symptoms. An example is a study conducted by Guardino and his team in 2004. In this study, out of 99 patients, 79 didn’t have any symptoms at the time of diagnosis. However, for those who showed symptoms, 12 of them had a urinary tract infection. Other signs found in this study included stomach pain in 4 patients, a palpable mass in the abdomen in 2 patients, and blood in the urine and inability to hold urine in others. Each sign was found in one patient.
In rare cases, a small or minute ectopic kidney located in the pelvic region could be the reason for constant urinary incontinence in females. This means they can’t control their bladder and leak urine all the time. Sometimes this kidney could be so small that ultrasound may not be able to detect it and advanced imaging techniques like a renal nuclear scan or MRI with contrast might be needed. This tiny kidney can cause an enlargement of the healthy kidney on the other side. If a woman has primary, constant urinary incontinence, doctors should suspect this condition. The typical treatment for this is the surgical removal of the ectopic kidney by laparoscopic or robotic means.
Testing for Pelvic Kidney
During prenatal ultrasound checks, if the baby’s kidney appears to be located in an unusual spot (ectopic kidney), particularly when the amniotic fluid is at a normal level, it’s crucial to conduct further investigation. These misplaced kidneys are typically the most common reason for an ultrasound showing an “empty” kidney space.
After the baby is born, further diagnostic steps might be different depending on the clinic but will likely include additional imaging. This is to check for a condition called hydronephrosis (when the kidney swells due to urine failing to properly drain from the kidney to the bladder) and to see the structure of the other kidney. If the tests don’t show any signs of issues, like hydronephrosis, and the kidney function is normal (based on creatinine levels, a waste product filtered by the kidneys), no further actions might be necessary. However, some doctors suggest more regular ultrasounds to monitor the kidneys’ growth and detect any early signs of hydronephrosis or kidney stones.
If severe hydronephrosis or urinary tract infections are present, then a voiding cystourethrogram (VCUG), a type of X-ray, may be required. If this test result appears normal, further evaluation resorting to a special kidney scan may be required. Especially if the creatinine level in the blood is high, it may signify an obstruction. However, if there is mild to moderate hydronephrosis, it may be recommended to repeat the scan after 3 to 6 months to monitor any worsening of hydronephrosis and check on kidney growth. In case of any abnormality, more comprehensive imaging and scans may be needed to identify possible obstructions in the ureter, the tube that carries urine from the kidney to the bladder.
If the other kidney has unusual structures or impaired functionality, doctors often suggest a DMSA scan. This test measures the health of the kidney tissue and checks if one kidney is doing more work than the other. It’s important to raise these tests with a specialist because ectopic kidneys sometimes have less functionality than the other one.
Research indicates that kidneys located unusually in the body often come with other issues. For instance, vesicoureteral reflux (a condition that allows urine to flow backward into the kidneys from the bladder) was found in 20-30% of the cases with an ectopic kidney. Other detected abnormalities include kidney dysplasia (when the kidneys don’t develop normally) and hydronephrosis. Some other non-urinary conditions may accompany the ectopic kidney, such as VACTERL anomalies, a name for a group of birth defects that often occur together. Therefore, once an ectopic kidney diagnosis is made, it’s essential to assess these other potential congenital defects.
Treatment Options for Pelvic Kidney
If you have a “pelvic kidney,” which is a kidney that’s located in your pelvis instead of its usual place in the abdomen, you usually won’t need any medical treatment if there are no complications. But if problems like kidney stones, known as renal calculi, occur, it could be trickier to deal with due to the unusual shape and position of the kidney.
If kidney stones develop in a pelvic kidney, treating them can be much more complex. This is because the tubes that carry urine from the kidneys to the bladder, known as ureters, are in a different location. One treatment option is a laparoscopic-assisted procedure, which is a minimally invasive surgery. This method has been used successfully to treat large kidney stones too big for a non-surgical treatment called shockwave lithotripsy, which is typically effective for kidney stones smaller than 2 cm.
This type of surgery might involve moving the colon, which could potentially cause a leak of urine into the abdomen. However, it could be an option if the stone is not located within the renal pelvis and calyces, the parts of the kidney where urine is collected. This movement of the bowel can be avoided by using another type of surgery — robot-assisted surgery. This has the added advantage as it remains within a space called the retroperitoneal space, reducing the risk of urine leaking into the abdomen and the chances of urinoma, which is a collection of urine within the body that’s not in the bladder.
It’s also worth noting that problems with pelvic kidneys can be tackled individually if needed. A fused renal mass (which is a kidney that’s stuck to another organ or tissue) should not be separated due to the risk of injuring blood vessels, tissue death, and reducing kidney function.
Large-scale surgeries are generally not encouraged for pelvic kidneys, except for specific problems. In most cases, they can be managed without surgery. However, certain procedures, like using a needle to access the kidney to relieve a blockage, could be more challenging or even impossible due to the unique anatomical structure. It’s important to consider this in treating pelvic kidneys.
If you’ve had kidney stones with a pelvic kidney, it’s recommended to do a 24-hour urine test. This is because the surgery for kidney stones in these individuals can be complicated, and there’s a risk of losing kidney function. The urine test can help prevent future kidney stones.
What else can Pelvic Kidney be?
When scanning with an ultrasound, we might notice some unusual results. It could be due to unique conditions that affect the formation or position of the kidneys:
- Unilateral Renal Agenesis: In this case, the ultrasound will only show one kidney, which might look like renal ectopia (dislocated kidney). But in renal agenesis, the kidney doesn’t form at all, as opposed to just not being in the right place.
- Horseshoe Kidney: This condition also causes the kidneys to be out of place. However, in this situation, both kidneys are fused together. They create a single U-shaped mass in the lower abdomen. This mass can often be identified easily on an ultrasound or other types of abdominal imaging studies.
In either case, further investigations are needed to accurately diagnose the condition and decide the right treatment strategy.
What to expect with Pelvic Kidney
Ectopic kidneys, or kidneys that are not in their typical place, usually don’t cause issues with kidney function or blood pressure if there are no other health conditions present. A study in 2010 looked at 41 patients who all underwent a certain kind of test. They found that these patients’ kidneys were working about 38% as effectively as typical kidneys, and that over 80% of them had relatively healthy kidneys, regardless of whether the kidney was simply out of place or also crossed over to the opposite side of the body.
However, if the kidneys are not only out of place, but also turned the wrong way and have a physical abnormality, then these patients are more likely to get repeated urinary tract infections and a buildup of urine in their kidneys. They also have a higher rate of a condition where urine flows back into the kidneys and even kidney failure, compared to people without these kidney issues.
“Pancake kidneys”, which are also ectopic but specifically flattened and fused together, usually don’t cause any symptoms. But they do increase a person’s risk of getting repeated urinary tract infections and kidney stones. This higher risk is due to the flow of urine being reduced through a twisted pathway, and blood vessel abnormalities related to the condition.
A review in 2019 found only a few cases of stones and cancers linked to a specific kind of ectopic kidney where the kidneys are fused together and crossed over to the opposite side of the body. However, these kidneys worked well enough that they could be used for kidney transplants.
While having an ectopic kidney is not free of complications, the overall outlook for those with this condition is usually positive.
Possible Complications When Diagnosed with Pelvic Kidney
People with kidneys located in the pelvis (known as pelvic kidneys) usually have a good prognosis. But their unique ureteral anatomy can interfere with normal urine flow and potentially lead to a number of health issues. This includes an increased risk of vesicoureteric reflux (backflow of urine from the bladder into the ureter), kidney stone formation, recurrent urinary tract infections (UTIs), and chronic kidney disease.
Vesicoureteric Reflux
Abnormal ureteric anatomy is often seen with ectopic kidneys (misplaced kidneys). This can cause the ureter to be twisted and its insertion point in the kidney to be higher than normal, impeding the flow of urine. This may result in backflow of urine into the kidneys (called vesicoureteric reflux or VUR), or the enlargement of the renal pelvis and kidney cavities (a condition known as hydronephrosis). The likelihood of these complications varies, with most studies suggesting they are relatively rare. Ultrasound is used to diagnose hydronephrosis, while VUR requires more investigation. The best method for diagnosing VUR is a type of X-ray called a voiding cystourethrography (VCUG), especially in patients with recurring UTIs and worsening kidney function.
Renal Calculi
The rate of kidney stone formation in people with pelvic kidneys is uncertain, but it’s believed to be higher than the general population due to the altered anatomy and slower urine flow. This atypical anatomy also has notable effects on the surgical management of kidney stones, and there’s a higher risk of damaging blood vessels during surgery compared to the general population.
Malignancy
Cancer in pelvic kidneys is rare, with the risk of developing cancer similar to people with normally positioned kidneys. However, some reports indicate that those with certain types of kidney malformations, such as horseshoe kidneys (when the kidneys are fused together), may have a higher likelihood of developing Wilms tumor or renal cell cancer than the general population. Precautions must be taken due to the variations in kidney blood supply during any surgical procedures on these patients.
Preventing Pelvic Kidney
For individuals who have an ectopic kidney (a kidney located in an unusual place), it’s vital to understand the situation because it can change the treatment options. You should openly communicate about your condition with the healthcare professionals taking care of you. This communication becomes especially crucial if you, over time, develop complications like vesicoureteric reflux – a condition where urine flows backwards into your kidneys from your bladder.
This reverse flow of urine can affect your long-term health. It can also lead to a higher chance of developing kidney stones, urinary tract infections, and a chronic condition called kidney disease, where your kidneys stop working as they should. Therefore, understanding this and having honest conversations with your doctor can help manage your condition better.