Urodynamics for Spina Bifida Patients

Posted by Clark Love on Sep 8, 2017 12:19:22 PM

urodynamics-spina-bifida.jpgSpina bifida patients have unique needs related to urologic care due to the nature of this disease. Here, routine urodynamics care for patients with spina bifida will be discussed.

 

What is Spina Bifida

Spina bifida1 is a birth defect that is characterized by the incomplete closing of the backbone and associated membranes around the spinal cord. While the lower back is the most common location for spina bifida, in rare instances children may experience this disorder in the neck or thoracic spine.

The mildest form of spinal bifida is occulta2, in which children are asymptomatic or have very mild symptoms. In this instance, children commonly have a spot on their back where a gap in the spine is located, such as a dimple, dark spot, swelling, or a hairy patch.

Meingocele is more serious than spina bifida occulta, but generally only causes mild problems due to the sac of fluid that is present at the spinal gap.

The most severe form of spina bifida is myelomengocele, which is also known as open spina bifida, and causes the spinal cord and adjacent structures to develop outside of the body. Children with spina bifida may suffer from incoordination, difficulties with bowel or bladder control, latex allergies, and a tethered spinal cord. While uncommon, spina bifida may also be accompanied by a learning disorder.

The exact cause of spina bifida is unknown, although researchers believe that both genetics and environmental factors are to blame. For parents who have one child with spina bifida, there is a 4% chance that subsequent children will also have this condition. Environmental factors include lack of folate in the mother’s diet during pregnancy, as well as anti-seizure medication, diabetes, and obesity. Depending on the severity of spina bifida, this condition can be diagnosed in the womb or at birth. Screening tools include blood test, aminocentesis (to look for high levels of alpha-fetoprotein), or ultrasound. Spina bifida is a form of a neural tube defect, related to anencephaly and encephalocele.

Treatment for severe forms of spina bifida, such as myelomengocele, includes surgery at birth to close the opening in the spinal column. In some instances, a shunt may be required when hydrocephalus is detected, and a tethered spinal cord will require surgical repair. If movement is restricted, children may be confined to a wheelchair or crutches. In almost all cases, the functioning of the lower urinary tract is affected, requiring children to undergo frequent urinary catheterization.  

Overall, approximately 5% of people worldwide have spina bifida occulta, but these rates vary widely by country, where environmental factors can be more or less controlled. In developed countries, such as the United States, spina bifida is much rarer, occurring in only 0.4 per 1,000 births. However, in India, spina bifida rates are significantly higher, at 1.9 per 1,000 births3.

How Does Spina Bifida Affect the Urinary Tract

The most common problem that children born with spina bifida face is neurogenic bladder. Due to the improper development of the spine, the nerves in the spinal cord which control the bladder do not form properly. Therefore, children might encounter problems either storing urine in the bladder, or voiding properly. In severe cases, both functions might be affected.

For nearly every child born with spina bifida, clean intermittent catheterization is necessary. This process is performed to protect the kidneys by preventing urinary tract infections, and to also allow children to have a higher quality of life by preventing the embarrassment that can be caused by diapers. Anticholinergic medications can be prescribed to help the bladder relax so that it can more effectively store urine while also helping to protect the kidneys.

In general, due to the neurogenic bladder, spina bifida patients have a much greater incidence of urinary tract infections than children without the presence of a neurogenic bladder. They also experience vesico-uretal reflux to a much greater degree, in which urine travels backwards from the bladder, through the ureters, and to the kidneys. This problem can occur due to high pressures in the bladder, and can result in kidney damage as infected urine spreads from the bladder. Hydroenphrosis is another kidney disorder, which is caused by high bladder pressures and results in swelling of the kidney due to the backup of urine. Finally, incontinence is a common concern for children with spina bifida, which can cause both physical and social problems for patients.

These problems occur because of nerve damage in the spinal cord which prevents the bladder and sphincter muscles from properly working together. Without this damage, the bladder is intended to fill and store urine at low pressures, and to empty every few hours. Both emptying and storage phases may be affected in spina bifida patients.

For instance, the bladder may not be able to operate at low pressures as it fills with urine. High bladder pressures, however, can cause damage to the kidneys. In addition, the bladder will not be able to hold as much urine as it theoretically should when bladder pressure is high, resulting in issues such as reflux or incontinence. In the emptying phase, urine leakage can occur if high bladder pressures weaken the sphincter muscles. Even at normal bladder pressures, urine leaking can occur if the sphincter is relaxed and does not tighten properly. Additionally, the bladder may not empty completely. This disorder can be caused by weak bladder muscles, or the sphincter muscle failing to relax when the bladder contracts.

In addition to affecting the urinary tract, spina bifida can also cause problems with a child’s bowels. Children with spina bifida are a greater risk for developing constipation because they lack the nerves which regulate bowel movements. In general, children with spina bifida rely on laxatives for the prevention of constipation.

Urodynamics

Urodynamics is a blanket term for a series of tests that assess the functionality of the lower urinary tract. These tests are important for the spina bifida patient to assess bladder pressure and storage / voiding phases. For non-spina bifida patients, these tests are ordered to diagnose issues such as urinary incontinence or prostrate problems, as well as completed before and after any type of surgery involving the pelvic organs or the urinary tract. Common symptoms that result in a doctor ordering urodynamics include incontinence, frequent urination, inability to urinate, weak urine stream, painful urination, nocturia, recurrent urinary tract infections, and difficulties emptying the bladder entirely.  The types of urodynamic tests commonly performed include the following:

  • Uroflowmetry is a test which measures a patient’s natural urine flow rate, as well as urine volume before and after voiding. Here, the patient is asked to empty his or her bladder naturally while a flow rate meter records urine flow. This test is routinely performed for all urodynamic assessments, and is useful when diagnosing the cause of weak urine stream or difficulty urinating. Additionally, uroflowmetry can determine how well a patient’s bladder and sphincter are functioning, and can be used to determine if obstructions are blocking the bladder from releasing urine.
  • Pressure uroflowmetry is like uroflowmetry described above in that it also measures the rate of urination. However, bladder and rectal pressures are also simultaneously recorded during this assessment. Pressure uroflowmetry requires invasive catheterization and is useful for diagnosing disorders that result in difficulty urinating. Common diseases that are diagnosed with this test are bladder muscle weakness and bladder outlet obstruction.
  • Post-void residual volume tests are used to measure the volume of urine that remains in the bladder after voiding. This test is important in the assessment of many urinary tract disorders. Here, the patient is asked to void his or her bladder naturally, and then a bladder scanner is used to noninvasively measure the amount of urine remaining in the bladder. If a bladder scanner is unavailable, the patient is catheterized and the remaining amount of urine is measured. Post-void residual volume assessments are primarily used to determine neurogenic bladder disorders as well as the cause of frequent urinary tract infections, renal insufficiency, bladder outlet obstruction, and detrusor underactivity.
  • Multichannel cystometry is a type of pressure uroflowmetry test. Two pressure catheters are inserted, one in the bladder and one in the rectum, to measure associated pressures during both the filling and emptying of the bladder. Assessments that are made include the presence of contractions in the bladder wall during filling or stress (i.e. coughing), urethra strength, detrusor under- or overactivity, and bladder outlet obstruction. This test is the gold standard for diagnosing stress urinary incontinence.
  • Electromyography is a test that measures the electrical activity in the bladder neck. It can be performed during voiding to determine coordinated or uncoordinated voiding and the functioning of the detrusor muscle. For this measurement, electrodes are placed in the pubic area of the patient to test for electrical impulses from the muscles. Most commonly, electromyography is beneficial when testing for neurologic disorders that affect the communication between the brain and body.
  • Urethral pressure profilometry measures strength of sphincter contractions. This test is used to further study urinary incontinence in both men and women.
  • Fluoroscopy (also known as videourodynamics) is a moving video x-ray of the bladder and bladder neck that is obtained while the patient is voiding her bladder. This test helps doctors provide a better view of what is happening in the lower urinary tract, such as bladder outlet obstruction or pelvic organ prolapse.

Ultimately, each of the tests described above is important for diagnosing various disorders of the lower urinary tract. These tests range from non- to minimally invasive and are performed as outpatient procedures. There is minimal pain or discomfort associated with each assessment, and few risks involved. Additionally, doctors are typically able to provide patients with immediate answers regarding their urinary symptoms.

Urodynamics in Spina Bifida Patients

There are multiple tests that are performed for both prevention and treatment of urinary disorders in spina bifida patients, and urodynamics for spina bifida patients is one of the most important.

A urinalysis and urine culture should be regularly performed to check for signs of infection due to problems voiding. Indeed, urinary tract infection4 is one of the most common side effects of neurogenic bladder, so testing for bacteria which might be present in the urine is important.

Renal and bladder ultrasounds are also routinely performed in spina bifida patients to visualize the size and shape of both the kidneys and bladder. Since storage of urine in the bladder is such a prevalent problem, spina bifida patients are at increased risk of organ damage. Regular ultrasound also ensures that the bladder and kidneys are developing properly in severe cases of spina bifida.

A voiding cystourethrogram (VCUG) may be performed to determine whether urine reflux is occurring, which is a condition where urine flows backwards into the kidneys. This condition can cause kidney damage. In addition to testing for reflux, a VCUG can be performed in place of a renal / bladder ultrasound, as it also shows the shape of both the bladder and the urethra, and can also provide information on how well the bladder voids itself of urine.

Traditional urodynamic studies, i.e. multichannel cystometry, are routinely performed for spina bifida patients. The parameters that are useful when treating neurogenic bladder include knowing the bladder’s storage volume, as well as the pressures that the bladder maintains during filling, storage, and voiding phases.

Pressure flow studies can also determine how well the bladder empties, as well as the functioning of the bladder and sphincter muscles in conjunction with one another. This test can also determine if reflux is present, and provides doctors with useful information as to which children with spina bifida may be at increased risk for developing problems in the lower urinary tract. Regular urodynamics is a good way to keep track of how well a child’s bladder is responding to treatment or for any new or worsening disorders, as well.

Non-urodynamic based tests that can be performed in children with spina bifida to keep track of the functioning of their urinary symptoms include blood tests to check creatinine and blood urea nitrogen (BUN) levels, as well as renal scans. Both tests measure how well the kidneys are functioning and whether there is a drainage issue from the kidneys to the bladder. A renal scan will also show whether scars are present on the kidneys, or if other changes have occurred that require attention.

Ongoing Urodynamics Care for Spina Bifida Patients

Urodynamic assessment is utilized throughout a child’s life to monitor symptoms and treatment of the spina bifida patient’s condition. For newborns with spina bifida, there are numerous urodynamic tests performed to assess the child’s urinary tract. A urinalysis and urine culture is the first step, which checks for signs of infection. Blood tests look for kidney damage by testing creatinine and BUN.

A post void residual test is also performed on the newborn to determine how much urine remains in the bladder after the child has voided. A bladder ultrasound looks for physical abnormalities, while traditional pressure flow studies are performed on the child during his or her first month of life to achieve baseline measurements and to check for abnormalities, such as high bladder pressure.

These initial urodynamic tests help pediatric urologists make suggestions for the child’s care. For instance, if the child shows signs of reflux, clean intermittent catheterization is started and low-dosage antibiotics prescribed to prevent infection. If high bladder pressures are detected, clean intermittent catheterization and anticholinergic medications are prescribed.

In the first year of the child’s life, renal ultrasounds and urodynamic studies are performed every 3 – 6 months to monitor the infant’s condition, as well as to check for new abnormalities. As the child grows, the bladder function is sometimes altered.

After the first year, toddlers should have renal ultrasounds every 3 – 6 months, and urodynamic studies performed every 6 months. Catheterized urine cultures should be obtained whenever the child shows signs of urinary tract infection.

When the spina bifida patient reaches preschool age, renal ultrasounds and urodynamic studies only need to be performed every 6 – 12 months. If, after potty training, the child is having difficulties with continence, clean intermittent catheterization should be started.

When the child reaches school-age, renal ultrasounds and urodynamic studies only need to be performed yearly, or as necessary. At this age, the child may be able to perform clean intermittent catheterization his or herself.

Finally, when the child reaches adolescence, urodynamic tests and renal ultrasounds should only be performed as deemed necessary by a urologist. Throughout the spina bifida patient’s life, catheterized urine cultures should be obtained whenever signs of urinary tract infection are obvious. As adults, spina bifida patients should know and understand the signs of urinary tract infection, and should be able to catheterize themselves for clean intermittent catheterization.

Conclusion

Ultimately, urodynamics testing plays an important role in the maintenance of spina bifida. Patients with this disease, particularly its most severe form – myelomengocele – are at an increased risk of neurogenic bladder, urinary tract infections, high bladder pressures, urine reflux, and kidney and bladder damage.

Without urodynamics, these conditions can go unnoticed and create serious and potentially life-threatening problems for spina bifida patients. Routine urodynamics testing is especially important for young children with spina bifida, and is performed as needed as the patient reaches adolescence. Overall, urodynamics is a technique that has vastly improved the quality of life of patients with spina bifida.

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 References

  1. Mitchell LE, Adzick NS, Melchionne J, Pasquariello PS, Sutton LN, Whitehead AS. Spina bifida. Lancet. 2004;364(9448):1885-95.
  2. Gregerson DM. Clinical consequences of spina bifida occulta. J Manipulative Physiol Ther. 1997;20(8):546-50.
  3. Bhide P, Sagoo GS, Moorthie S, Burton H, Kar A. Systematic review of birth prevalence of neural tube defects in India. Birth Defects Res Part A Clin Mol Teratol. 2013;97(7):437-43.
  4. Vigil HR, Hickling DR. Urinary tract infection in the neurogenic bladder. Translational Andrology and Urology. 2016;5(1):72-87. doi:10.3978/j.issn.2223-4683.2016.01.06.

Topics: Urodynamics Testing, Pediatric Urodynamics, Spina Bifida

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