Myelomeningocele
With regard to embryology, the developing spinal canal begins on the 18th day of gestation and is completed by day 35, closing in a caudad direction from the cephalic end of the body. Failure of mesodermal in-growth over the developing spinal cord results in an open lesion, most commonly seen in the lumbo-sacral area and, with decreasing regularity, in the thoracic and cervical areas (Table
1). The exposed spinal cord and its nerve roots, some of which may protrude into the meningocele sac, and tension on the spinal cord as the cord ‘rises up’ the canal with elongation of the fetus (from L2, L3 in mid- to late fetal life, to L1 at birth), contribute to a variable picture of neural injury to the lower urinary tract and lower extremities [
8]. Coupled with obstruction of the aqueduct to the fourth ventricle (Chiari malformation), with possible herniation of the brainstem and the center for micturition coordination (the pontine mesencephalic center), additional layers of dysfunction are added to those nerve pathways already affected.
Table 1
Spinal bony level of myelomeningocele (uppermost vertebral abnormality)
Cervical-high thoracic | 2 |
Low thoracic | 5 |
Lumbar | 26 |
Lumbosacral | 47 |
Sacral | 20 |
The over-riding issue at birth is whether or not the child has detrusor external urethral sphincter dyssynergy and whether the infant can empty the bladder completely at low pressure. All newborns with radiologic abnormalities at birth (5–10% with hydronephrosis, reflux) have active obstruction of the bladder outlet that had caused these changes to occur in utero [
9]. The presence of elevated detrusor filling pressure, bladder sphincter dyssynergy or high voiding or leaking pressures (above 40 cm H
2O) at capacity, which can result in upper urinary tract deterioration in as many as 63% of children [
9], warrants early intervention with clean intermittent catheterization (CIC) and anticholinergic drugs [
10‐
13]. Thus, the investigation of these children when newborn includes a renal and bladder ultrasound, a catheterized measurement of urine residual after voiding or leaking, a determination of serum creatinine concentration after 7 days of life and a urodynamic study that incorporates both detrusor pressure measurements and urethral sphincter electromyography. Voiding cystography is undertaken when hydronephrosis is present and/or urodynamic studies indicate bladder outlet obstruction with either increased pressure at capacity or bladder sphincter dyssynergy. The incidence of reflux when there is functional obstruction of the bladder outlet can range as high as 50% [
14,
15].
Although some clinicians still preach watchful waiting if the renal ultrasound findings are normal, and do not recommend urodynamic studies in the newborn period, opting instead for instituting CIC and drug therapy only with the first sign of ureteral or renal pelvic dilation [
16,
17], most centers within the USA now advocate full investigation of the lower urinary tract and initiate prophylactic treatment if there are signs of outlet obstruction and/or elevated bladder filling or voiding pressure [
18‐
20]. The incidence of urinary tract deterioration can be greater than 50% [
11,
12,
20] when children with the potential for deterioration are followed with expectant and not preemptive therapy. Even though the ‘watchful waiters’ demonstrate that they can reduce the presence of hydronephrosis and, possibly reflux, the changes in detrusor dynamics are not as easily reversed, and the need for subsequent aggressive management of the bladder to control incontinence and a poorly compliant bladder is commonplace (Table
2). Therefore, CIC is begun when detrusor sphincter dyssynergy, elevated leak point pressures greater than 40 cm H
2O, and/or reflux grade 3 or higher (on a scale of 1 to 5) are present. Instituting CIC and anticholinergic therapy in infancy has revealed many advantages over time [
19‐
21]: the parents and the child adapt to the routine of CIC much easier than they would have if it were to be begun when the child is older; the bladder often remains very compliant, expanding as the child grows and maintaining appropriate wall thickness as noted on bladder echography; hydronephrosis and vesicoureteral reflux develop in fewer than 10%; continence is readily achieved in greater than 50% with no additional maneuvers; and the need for augmentation cystoplasty to maintain a reasonable organ for storage is markedly reduced from almost 60% to 16% when compared with that in children followed expectantly [
22].
Table 2
Surveillance in infants with myelodysplasia (until age 5 years) (IVP intravenous pyelogram, ECHO sonogram, UDS urodynamic study, VCUG voiding cystourethrogram, RNC radionuclide cystogram)
Intact-synergic | Post-void residual volume | Every 4 months |
IVP or renal ECHO | Every 12 months |
UDS | Every 12 months |
Intact-dyssynergica
| IVP or renal ECHO | Every 12 months |
UDS | Every 12 months |
VCUG or RNCb
| Every 12 months |
Partial denervation | Post-void residual volume | Every 4 months |
IVP or renal ECHO | Every 12 months |
UDSc
| Every 12 months |
VCUG or RNCb
| Every 12 months |
Complete denervation | Post-void residual volume | Every 6 months |
Renal ECHO | Every 12 months |
When vesicoureteral reflux is present, CIC effectively lowers the intravesical emptying pressure when the bladder is drained. In addition, anticholinergic medication can be added to lower detrusor filling pressure, increasing compliance without fear of causing urinary retention when combined with CIC. The lowered filling and emptying pressures has proven to be very beneficial; in 30–50% of children reflux is resolved within 2–3 years of its discovery and initiation of therapy.
The disadvantages are few and include a higher rate of bacteriuria (60–70% versus 30%) but a lower rate of symptomatic urinary tract infection (20% versus 40%) during childhood than in children followed expectantly [
23,
24]. Because the subsequent risk of reflux is lower, the effect on renal function and the development of scarring is reduced when these prophylactically treated children are compared to those monitored with watchful observation [
16,
25].
Credé voiding is not an efficacious form of bladder emptying in children with myelodysplasia, especially if the urethral sphincter is partially or fully innervated. Because most children have intact motor function above L1, any increase in abdominal pressure from a Credé maneuver can lead to a reflexive increase in urethral sphincter activity, thus producing an increase in bladder outlet resistance resulting in “high voiding pressure”. This can be particularly noxious in children with moderate or severe grades of reflux. In addition, as the child grows, the bladder resides more in the pelvis and not intra-abdominally, further reducing the effectiveness of the Credé maneuver.
The key to a stable bladder and, consequently, renal function is the maintenance of a good capacity, highly compliant, detrusor muscle, combined with periodic and complete emptying of the bladder at low pressure. Anticholinergic medication (primarily oxybutynin, tolterodine, glycopyrrolate, hyoscyamine or trospium) and CIC achieve that in a majority of children and provide an added benefit of continence if the child has reasonable bladder outlet resistance [
9]. Several alpha sympathomimetic agents, such as phenylpropanolamine, ephedrine or pseudoephedrine, are used to increase bladder outlet resistance when it is not sufficient to maintain continence between CICs. A variety of surgeries has been devised when these conditions cannot be met. A detailed description of the surgical treatment is beyond the scope of this discussion, but, suffice it to say, bowel augmentation onto the bladder has been a common practice to lower pressure and increase capacity in order to make the bladder a useful organ for storage. Disadvantages abound, including problematic mucus production, recurrent urinary infection, electrolyte imbalance, stone formation and the recently documented risk for the late occurrence of cancer in the augmented segment [
26].
A plethora of surgical procedures has been designed to increase bladder outlet resistance in those children with a level that is insufficient to maintain continence between catheterizations, that include implantation of an artificial urinary sphincter, bladder neck tightening, using adjacent tissue, a fascial sling, and various bulking agents. All can provide more resistance, but no one procedure is ideally suited for every patient.
Creating a catheterizable urinary stoma has become fashionable in those children with intractable urethral incontinence (with obliteration of the bladder neck) or inability to catheterize their urethra easily due to obesity, poor eye–hand coordination or caretaker issues surrounding genital organ privacy. Long-term success has been achieved that provides the individual with a degree of independence, but problems with stomal stenosis can occur.