Urinary outflow tract obstructions

OVERVIEW: What every practitioner needs to know

Acute urinary retention in the pediatric population is much rarer and has a wider range of etiologies than seen in adult men. Clean intermittent catheterization is the mainstay of management once the practitioner establishes that the amount of urine in the bladder equals or exceeds the age-related estimated capacity. All children presenting with retention must be worked up for possible underlying neurologic, infectious or inflammatory conditions.

Are you sure your patient has a urinary outflow tract obstruction? What are the typical findings for this disease?

In acute urinary retention, the patient is unable to void for 12 hours despite the presence of a full bladder. Full bladder volume (in mL) is estimated as (age+2)*30=age appropriate capacity. Abdominal pain is commonly an accompanying or sole presenting symptom.

What other disease/condition shares some of these symptoms?

Anuria or oliguria are by far the most common diagnoses that are mistaken for urinary retention; therefore, the clinician must establish that the patient is producing urine and that it is present in the bladder. This can be done with physical exam or imaging.

What caused this disease to develop at this time?

Neurologic: encephalitis, Guillain-Barré syndrome, transverse myelitis, neoplasms of the spinal cord (ependymoma, Ewing sarcoma, neuroblastoma), occult dysraphism, tethered cord, traumatic injury
Voiding dysfunction: Fowler’s syndrome, Hinman-Allen syndrome
Urinary tract Infection (UTI)
Constipation
Adverse drug reaction: anesthetics; neuroleptics such as phenytoin, carbamazepime, haloperidol. Cold medicines and antihistamines such as pseudoephedrine, brompheniramine, diphenhydramine.
Inflammatory conditions: appendicitis, meatal stenosis, balanitis, labial adhesions, incarcerated hernia.
Malignancy with local invasion: Bladder/prostatic rhabdomyosarcoma, lymphoma, retroperitoneal testis or other neoplasms
Benign obstructing lesions: Posterior urethral valves, urethral stone, ureterocele, imperforate hymen, ovarian cyst, urethral polyp or stricture
Trauma: Iatrogenic, pelvic fracture
Idiopathic-Less than 10%

What laboratory studies should you request to help confirm the diagnosis? How should you interpret the results?

Urinalysis and culture. Basic metabolic panel to check if renal failure is also present.

Would imaging studies be helpful? If so, which ones?

Bladder scanner: note that these will produce erroneously high readings in patients with recent abdominal surgery, ascites, or other concurrent abdominal processes.
Pelvic ultrasound if the above is not available or a condition mentioned above is present.
Abdominal plain film or KUB to assess for constipation.
MRI of the spine if neurologic cause is suspected.
CT/MRI of abdomen/pelvis if malignancy is suspected.
Voiding cystourethrogram (VCUG) if benign obstruction is suspected. May also be useful after resolution of febrile or recurrent UTI.

Confirming the diagnosis

Diagnosis is based on patient history, physical examination, and ultrasound imaging to confirm full bladder.

Patient history should include preceding events, voiding dysfunction (daytime incontinence, nocturnal enuresis, frequency, urgency, dysuria, history of urinary tract infections or stones), constipation, gross hematuria, medication and toxin exposure, and prenatal ultrasounds.

Physical exam should include palpation for a full, possibly tender, bladder. In older children, this will be felt as a mass one to two finger breadths above the pubic symphysis, whereas in infants and toddlers, this can be felt as an abdominal mass. Also, one must look for stigmata of occult dysraphism such as a sacral dimple or hair-bearing patch over the spine. Motor and sensory exam. Rectal exam to assess tone and presence of stool or mass.

If you are able to confirm that the patient has a urinary outflow tract obstruction, what treatment should be initiated?

Immediate intervention is the initiation of clean intermittent catheterization until treatment of the underlying issue resolves the obstruction/retention. Indwelling urethral or suprapubic catheters should usually be avoided as they have higher rates of infection.
UTI: Empiric antibiotics until culture and sensitivities define an appropriate narrow spectrum antibiotic.
Voiding dysfunction/constipation: Miralax or other stool softener, timed voiding, urologic referral for possible urodynamic assessment
Mass/Malignancy: Appropriate referral for medical, surgical, or radiation therapy
Adverse drug reaction: Stop the inciting medication or eliminate exposure to toxin.
Neurologic: Referral to neurology or neurosurgery for appropriate management.
Benign obstructing lesion: Referral to urologist for removal of stones, ablation of posterior urethral valves, lysis of labial adhesion, rupture of imperforate hymen, resection of urethral polyp, treatment of urethral stricture, etc.

What are the adverse effects associated with each treatment option?

The most common adverse effect to urethral catheterization is iatrogenic urinary tract infection. Clean intermittent catheterization has a significantly lower rate of infection compared with indwelling suprapubic or urethral catheters. Trauma to the urethra can result in bleeding or creation of false passages.

What are the possible outcomes of urinary outflow tract obstructions?

Prognosis is highly variable and dependent on the underlying etiology. Recovery of normal voiding dysfunction and time to resolution depend on the degree of obstruction, amount of bladder distension, presence of perforation, and presence of renal failure.

Long-term consequences may include urinary incontinence, requirement of intermittent catheterization, and renal failure.

Intermittent catheterization is more labor intensive than indwelling catheters, but is the treatment of choice due to its decreased rate of infection. Urethral catheterization has the highest infection rate and may cause urethral erosion over time. Suprapubic tubes are intermediate between the two with regards to infection and are less likely to cause trauma to the urinary tract, but they do require a more invasive procedure. Indwelling catheters may be required if catheterization is too difficult or if the bladder has perforated.

What causes this disease and how frequent is it?

Urinary retention is rare in the pediatric population with the exception of children with known neurologic disorders (spina bifida, spinal cord injuries, etc.).

Incidence is more common during infancy or toilet training years as subtle neurologic conditions are discovered. The only seasonal variation would depend on use of cold or allergy medications.

Bacterial urinary tract infections account for a minority of cases. Transmission is most commonly ascending migration from the rectum and perineum.

Post-operative recovery period due to pain, narcotics and anesthetic.
One case report describes an association with deletion on chromosome 10q.

How do these pathogens/genes/exposures cause the disease?

All of the above etiologies either cause mechanical obstruction of the genitourinary tract caudal to the bladder or prohibit effective muscular contraction of the bladder.

Other clinical manifestations that might help with diagnosis and management

N/A

What complications might you expect from the disease or treatment of the disease?

Acute: Bladder perforation, renal failure, cardiac arrhythmia, increased ventricular pressure in spina bifida patients with a ventriculoperitoneal shunt

Chronic: Renal failure, voiding dysfunction/urinary incontinence

Are additional laboratory studies available; even some that are not widely available?

Follow up: Video-urodynamics or complex uroflowmetry if ongoing voiding dysfunction is suspected.

How can urinary outflow tract obstructions be prevented?

Miralax to prevent constipation.

Minimize anesthesia during surgery. For example, using local penile blocks instead of caudal/epidural for pelvic surgery.

Timed voiding regimen, typically every 2 to 3 hours.

Bowel regimen with scheduled trips to the toilet, typically three times daily.

Genetic counseling is indicated only if the underlying etiology warrants it. For example, mitochondrial disorders may sometimes present with urinary retention as well as other stigmata.

Encourage high intake of fruits, vegetables, high fiber, and fluid intake to prevent constipation in susceptible children.

What is the evidence?

Due to the rarity of this condition, all evidence comes from case reports or case series. An excellent review article on this condition is:

Gatti, JM, Perez-Brayfield, M, Kirsch, AJ. “Acute urinary retention in children”. J Urol. vol. 165. 2001. pp. 918-21.

Ongoing controversies regarding etiology, diagnosis, treatment

Despite strong data supporting intermittent, as opposed to indwelling, catheterization; many practitioners continue to use indwelling devices. This could be due to social issues or desire/need to limit the labor intensity.

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