Page 4 - Diagnosis, management, and surveillance of neurogenic lower urinary tract dysfunction – Full text

Kavanagh et al

tion, microscopic hematuria, and unexpected pyuria or pro- not be applicable to adult NLUTD. As DLPP increases, so
teinuria), and post-void residual (PVR) volume measurement. too does the risk of renal dysfunction due to an increased
Urine dip may need to be followed by a urine microscopy resting pressure in the bladder being transmitted to the kid-
and must be interpreted in the context of catheter usage. In neys. If a high DLPP only occurs at a volume greater than
patients who are voiding spontaneously, using reflexive void- the usual capacity during the normal daily voiding pattern,
ing/crede emptying, or using a condom catheter, the detection then this DLPP may not be physiologically relevant. A low
of an elevated PVR is important to address potential UTI risk DLPP maintains low pressure drainage from the kidneys,
and overflow incontinence and may prompt screening for however, this often results in urinary incontinence.
upper tract deterioration. It is important to recognize that a
PVR at the time of renal ultrasound may be artificially ele- Imaging
vated secondary to the hydration protocol, resulting in blad-
der over-distension; an elevated PVR from a renal ultrasound Renal and bladder imaging is necessary to identify hydrone-
should be confirmed in a more normal setting. phrosis (a late but potentially reversible sign of bladder dys-
PVR is not clearly defined as a factor associated with function in NLUTD), renal/bladder stone disease, abnormal
increased risk of complications among patients with bladder morphology (for example, thickened bladder wall,
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NLUTD. In the non-NLUDT population, a value >300 diverticula), and both renal atrophy and degree of scarring;
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mL is used to define chronic urinary retention. In NLUTD both SCI and SB patients are at an increased risk of renal
patients with a PVR >300 mL, it is reasonable to follow them stone disease, and this may present with atypical symptoms
for a period of time to determine the stability of their PVR (such as nausea or decreased appetite). 41-43 Often bladder
and bladder symptoms. PVR needs to be interpreted based stones are asymptomatic and early treatment, while they
on the proportion of urine voided and method of bladder are amendable to endoscopic management, is preferable.
emptying. The need to treat PVR should be based on patient
symptoms rather than an absolute number. Renal function
Specific patient populations require further investigation
due to a higher risk of serious sequela from bladder dysfunc- Patients with SCI and SB are at increased risk of renal dys-
tion. The first evaluation of a patient with SB, SCI, or a patient function; a serum creatinine can be used to assess renal func-
with more advanced MS should include UDS, renal-bladder tion, however, it may not accurately reflect renal function
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imaging, and a measurement of renal function. in these two populations. Evaluating the creatinine in the
context of previous readings is potentially useful, although
Urodynamics (UDS) it is important to note that changes within the normal range
may still be significant. Either a nuclear medicine glomerular
They are the gold standard for evaluating NLUTD and are filtration rate (GFR), or a 24-hour urine collection for creati-
necessary due to the absence of normal lower urinary tract nine clearance will better reflect renal function, and allow
sensation and the poor ability of symptoms to predict high- the identification of early renal dysfunction. While renal dys-
risk features. VideoUDS are preferred, as the additional function secondary to bladder dysfunction can occur with
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correlation with imaging allows assessment of VUR, abnor- MS, it is quite uncommon (estimated at 0.5%).
mal bladder morphology, and the behaviour of the urinary
sphincters during voiding. The availability of videoUDS is Cystoscopy
not universal, and a voiding cystogram is an acceptable
alternative in some cases. Urodynamic diagnoses, such as This should be reserved for situations where there is a clini-
neurogenic detrusor overactivity (NDO), impaired compli- cal indication to assess either the urethra or bladder (such
ance, reduced bladder capacity, or a high detrusor leak point as suspicion of urethral strictures or false passages, bladder
pressure (DLPP, defined as the lowest vesical pressure at stones, or bladder cancer). Screening cystoscopy has histori-
which urine leaks from the bladder in the absence of a cally been recommended among patients with indwelling
detrusor contraction or increased abdominal straining) can catheters or after SCI, however, there is no evidence that
identify a patient with potentially higher risk of urological screening programs are effective. Cystoscopy has a poor
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complications (such as renal dysfunction, urinary infections, sensitivity for bladder cancer in SCI patients; the higher-risk
and incontinence). 36-39 Other potential urodynamic charac- cancers after SCI are rarely detected at an early enough stage,
teristics, such as the duration of the NDO contraction, may which would affect their natural history, and there is very low
also predict renal deterioration. A DLPP of >40 cmH O real-world compliance with cystoscopy screening programs.
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2
has traditionally been cited as the cutoff above which a However, there does seem to be an increased risk of bladder
patient has a high risk of renal deterioration; however, this cancer in patients after SCI, potentially as a result of indwell-
is based on a historical study of children with SB, and may ing catheter usage, and cystoscopy should be used when

E160 CUAJ • June 2019 • Volume 13, Issue 6