BIOMED - Pathophysiology

🚽 𝘗𝘰𝘴𝘵𝘦𝘳𝘪𝘰𝘳 𝘜𝘳𝘦𝘵𝘩𝘳𝘢𝘭 𝘝𝘢𝘭𝘷𝘦𝘴 (𝘗𝘜𝘝)

©️ Monash Children's Hospital

A video to get started (4:52 mins):

Posterior Urethral Valves (PUV)

PUV is a congenital condition that affects males, involving an abnormal valve in the urethra that causes urinary obstruction. This occurs in around 1 in 4'000-6'000 male births, and is of unknown cause as of yet. It has however been associated with dysplastic kidneys (under-developed kidneys).

In PUV, the bladder must work harder to expel urine past the obstruction, thereby increasing pressure in the urinary tract. However this can also push urine back up the ureters into the kidneys and cause hydronephrosis as well as bladder distension.

The bladder wall can become thickened from higher pressures, and ureters do not work properly due to the distension and back-pressure.

Signs & Symptoms
Neonates with PUV may present with different symptoms, depending on the severity and timing of presentation. Depending on the obstruction and interruption to urinary flow, there will be urinary tract dilation seen on prenatal ultrasounds during pregnancy. There will likely be little amniotic fluid, as this is determinant on urine output, and if there is none, there will be less amniotic fluid, thereby affecting lung development in the fetus. Prenatal surgical intervention is only undertaken in severe cases, as this can be a risky surgery.

If it is not identified during pregnancy, there may be signs including:

☞ No urine output or a poor urine stream.
☞ Poor feeding & failure to thrive
☞ UTI's
☞ Abdominal distension

Older children may present with:

☞ Recurrent UTI's
☞ Difficulty/frequent voiding
☞Poor urinary stream
☞ Protracted bed wetting
☞ Poor weight gain or growth

Diagnostics
Ultrasound ☞ shows distension of the bladder, ureters, kidneys and upper urethra, and assists in determining risk to kidneys.

Blood Tests ☞ assess and monitor kidney function.

Micturating Cystourethogram (MCU) ☞ gives a definitive diagnosis, by ways of urethral catheter insertion to inject contrast and view through x-ray the shape and outline of the bladder as well as the urethral obstruction. This will show whether there is reflux of urine through the ureters into the kidneys.

Cystoscopy ☞ confirms the diagnosis if necessary and can be used to treat the condition at the same time. Under anaesthesia, this test assesses kidney function.

Treatment
Treatment aims to address the obstruction and manage bladder dysfunction. A catheter is inserted to drain urine whilst stabilising kidney function. Valve ablation via cystoscopy is the procedure used to address the obstruction, however may only be carried out until the baby's condition is stable.

If this is not successful, in critically ill babies, there are other options, including stoma formation in the form of vesicostomy, ureterostomy, and pyleostomy.

Complications of pUV
If there is damage to the kidneys, the baby will need to see a nephrologist, as impaired kidney function can progress to end-stage renal failure, and about 1/3 of boys will eventually require dialysis or renal transplantation at some point in their life.

These boys are also more prone to UTIs due to the poor urine drainage of bladder and ureters. A UTI that makes it to the kidney can cause more damage to renal function, and thus preventative and acute management is principal.

Bladder dysfunction may be experienced, as patients tend to experience overactive bladders. This causes in intense, upper urinary tract dilation and damages kidney function.

Outcomes Long-Term
This depends on the degree of kidney damage and bladder abnormality, as surgery does not reverse damage. As discussed, around 1/3 of boys with PUV will develop kidney failure requiring renal replacement therapy. 1/3 will also have renal impairment requiring medical/diet management, and 1/3 will go on to have normal kidney function, but may potentially experience issues with urinary tract drainage, infections and/or bladder function.

Follow-up is necessary, however frequency will depend on the condition of the patient and the type of issues being experienced. This will determine whether a urologist or nephrologist will be either or both involved in the management care.

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