Bladder outlet obstruction in children

postgraduate surgery presentation

1. Bladder Outlet Obstruction Presenter : Dr PASHI Moderator : Prof Munkonge

2. Introduction BOO describes blockage of urine outflow from the bladder and through the urethra Obstruction may be partial or complete C hildhood Urethral obstruction are mostly congenital O nly posterior urethral valves commonly give rise to secondary changes in the upper renal tracts Compared with the adult kidney, the developing kidney is highly susceptible to injury from obstruction to urine flow T he earlier the obstruction develops the worse the impact on the upper tracts

3. Incidence Various causes of BOO and vary in incidence In Africa, reports on the incidence are scanty, probably Voiding dysfunction describe abnormalities in either the filling and/or emptying of the bladder C onstitutes 40 % of paediatric urology clinic visits .

4. The Urinary system The urinary tract includes two kidneys, two ureters, a bladder, and a urethra . U rine flows from the kidneys through the ureters to the bladder which stores urine until releasing it through the urethra by urination Lower urinary tract – bladder and urethra Obstruction may occur anywhere More common in males

5. Embryology L ower urinary tract development is closely interrelated with genital tract and the hindgut. 3rd week of gestation, the cloaca meets the ectoderm of body wall at cloacal membrane 5th week , cloaca divided by urorectal septum to form the primitive rectum posteriorly and urogenital sinus anteriorly A llantois , bladder, pelvic, and phallic portions of the urogenital system are recognisable in the 6 th week.

6. Embryology

7. Embryology 7th week gestation, the mesonephric ducts (vas deferens) shift further caudal in the sinus and come to lie close to each other M etanephric buds (ureters) arise from mesonephric ducts root of the mesonephric duct exstrophies into the posterior wall of the developing bladder This process brings the openings of the ureteric buds into the bladder wall mesonephric duct is carried inferiorly to the level of the pelvic urethra The triangular region of exstrophied mesonephric duct incorporated into the posterior bladder wall forms the trigone of the bladder

8. Embryology

9. Embryology 9th week of gestation, the bladder cavity expands, urachus elongates and continues with the allantoic stalk at the umbilicus. 12th week gestation, extra embryonic allantois degenerates, urachus closes forming the median umbilical ligament. BOO manifest in some foetuses with closure of urachus , but delayed closure may protect others .

10. Embryology The early bladder epithelium initially consists of a single cell layer, but later become transitional B ladder epithelium or Chwalla’s membrane temporarily covers and occludes the ureteral orifice B ladder muscle arises from mesenchyme as a longitudinal layer on the dorsal surface and spreads cephalad to the intrarenal collecting system 16th week of gestation, the bladder is completely muscularized and the urachus is closed

11. Developmental Anomalies Bladder Agenesis : rare, is due to failure of allantoic stalk to develop U rachal anomalies (e.g., patent urachus ) result from delayed closure of the urachus , that arise from lower urinary tract obstruction at less than 12 weeks gestation Some anomalies result from a general mesodermal failure (the urachal diverticulum of the Prune belly syndrome). Intravesical ( simple) ureterocoeles are thought to be due to the persistence of Chwalla’s membrane beyond the time when urine flow begins

12. Bladder outlet obstruction caused by the urethral obstruction of posterior urethral valves or urethral hypoplasia may be detected from 4 weeks gestation concurrent with the absorption of the mesonephric duct and the resorption of the urogenital membrane. Abnormal dilatation of Cowper’s glands may give rise to an obstructive urethral syringocele

13. Bladder Innervation A utonomic nervous system P arasympathetic (S2–S4) S ympathetic (T11–L2 ) Inhibit parasympathetic to allow detrusor relaxation and expansion Constrict internal sphincter S omatic nervous system ( pudendal nerve(S1–S4) Control external sphincter

14. Physiology of voiding N ormal voiding cycle is a two-phased process, consisting of low-pressure and adequate volume bladder filling complete evacuation of the bladder . Bladder filling is passive determined by Vesicoelastic properties of the bladder wall Inhibition of bladder contraction Increased urinary sphincter Urinary continence maintained by contraction of sphincter complex which keeps urethral pressure above normal bladder pressure

15. Physiology of voiding Normal voiding is a spinal reflex modulated by the CNS (brain, pontine micturition centre, and spinal cord), which coordinates the functions of the bladder and urinary sphincter As the bladder fills, the pudendal nerve becomes excited, resulting in contraction of the external urethral sphincter As the bladder approaches fullness, tension receptors in the bladder wall trigger afferent nerves that send signals of the need to void. Voluntary voiding involves inhibition of sphincter contractions and coordinated contraction of the bladder smooth muscle.

16. Physiology of voiding Bladder filling in neonates is followed by reflexive emptying This micturition cycle occurs hourly under sacral spinal cord control After 6 months of age, the urinary volumes increase, the frequency of voiding decreases as the control of voiding shifts from the sacral cord to the pontine voiding center B rain maturation and development, leads to bladder and urinary sphincter control to inhibit involuntary voiding At 2 years the child develops conscious sensation of bladder fullness and has urge incontinence

17. Physiology of voiding Between 2 and 4 years of age acquires voluntary control of bowel and bladder function according to the following sequence: 1. nocturnal bowel control 2. daytime bowel control 3. daytime bladder control 4. nocturnal bladder control . B y 4 years of age , most children demonstrate adult voiding pattern . The timing of this sequence is influenced by ethnic, cultural, economic, and individual family differences.

18. Pathophysiology of BOO BOO results in an elevation of intravesical storage pressure Detrusor muscles generate excessive force against outlet resistance Massive hypertrophy of the detrusor muscles results Formation of sacculation , trabeculation, and ultimately diverticula The antireflux mechanism of the ureterovesical junction becomes incompetent Ureteral peristalsis is overcome increased hydrostatic pressures are transmitted directly to the nephron Results in impairment of renal development and function

19. Pathophysiology of BOO

20. Pathophysiology of BOO GFR falls as pressure in the proximal tubule and bowman space increase After 12–24 hours of complete obstruction, intratubular pressure decreases to preobstruction levels If not relieved, a depressed GFR is maintained by decreases in renal blood flow mediated by thromboxane A2 and angiotensin II With continued obstruction, there is a progressive fall in renal blood flow, ischaemia, and nephron damage. GFR falls, but tubular function is particularly severely affected, with a high water and sodium loss resulting in the high output renal failure of obstructive nephropathy.

21. Pathophysiology of BOO In the foetus, the placenta functions as the primary excretory organ in place of the kidney throughout gestation. Hence, in the new-born with BOO, the renal function is usually similar to the normal maternal levels initially because of the placental function. The kidneys commence gradual glomerular filtration by the 11th to 12th weeks of gestation. About 90% of amniotic fluid is produced in the kidneys, and only 10% comes from the GIT, lungs, and skin.

22. Pathophysiology of BOO Inadequate foetal urine production leads to oligohydramnios lung movement is therefore restricted P oor acinar growth and decreased surfactant production due to decreased fluid in the bronchial tree The newborn may have compressed limbs, Potter’s facies , and pulmonary hypoplasia presenting with respiratory distress and pneumothorax

23. Pathophysiology of BOO The pathophysiology of this process is complex and incompletely understood. Long-term bladder dysfunction may plague these patients in their daily lives despite relieving the obstruction. Obstruction impacts renal concentrating ability, glomerular filtration rate, and renal morphology.

24. Classification Primary causes : Anatomical ( congenital or acquired) functional (congenital or acquired) A natomical causes Intraluminal Intramural extrinsic . F unctional causes Neurogenic N onneurogenic

25. Aetiolgy Congenital urinary anomalies Male Female Posterior urethral valves Vaginal obstruction Anterior urethral valves Urogenital sinus Posterior urethral polyps Cloacal abnormalities Urethral diverticulum, atresia, duplication, stricture Ureterocele Prune belly syndrome Acquired urogenital anomalies Bladder neck fibrosis Trauma Urethral strictures Tumors

26. Clinical Presentation History Elicit prenatal health, birth and development, perinatal complication, and bowel and bladder habits. Many are asymptomatic for a long time or present with constitutional features that often are misleading to an unsuspecting practitioner A cute or chronic urinary retention, overflow incontinence, UTI, or renal failure.

27. Neonate P resentation is characterised by abdominal distention palpable suprapubic or flank masses (bladder and the kidneys); And/or urachal cyst, fistula, or abscess. Neonatal sepsis and respiratory distress may also be present. Parents may give a history of urine dribble, poor stream, and failure to thrive in the young infant

28. Infants and children E nuresis , weight loss, vomiting, and diarrhoea. Constipation may be present in cases of dysfunctional voiding, faecal impaction, Hirschsprung’s disease, or compression from pelvic masses. Other features include urine dribbling, incontinence, straining, frequency, and intermittency or “staccato” stream.

29. Physical Examination In the African setting, many children present with complications , due to late presentation and lack of prenatal diagnosis small stature for age, anaemia , gross pitting pedal oedema, ascites , and abdominal masses

30. Physical examination Other features depend on primary or secondary causes. SPINE examine for defects, and the lower extremities for reflexes, muscle mass and strength, sensation, and gait. PERINEUM check for gluteal fold symmetry, natal cleft depth, absent coccyx, perineal sensation, tone and reflexes. D igital R ectal E xamination check anal sphincteric tone, faecal impaction, distended rectum, and presacral and pelvic masses .

31. Investigations Depend on availability and condition A variety of tests may be required to confirm the diagnosis and determine the extent of damage I maging may be sufficient to define: site and extent of an obstructing pathology; extent of urinary tract reaction to the BOO split and total renal function and scarring; presence and degree of reflux; and associated anomalies, where present.

32. Investigations Haemogram to quantify anaemia. The platelet count may also drop. Serum biochemistry to assess the electrolytes, urea, creatinine, and acid-base balance

33. Investigations Plain radiography can identify radio-opaque stones. May suggest an enlarged or poorly emptying bladder, displacement of the bowel shadow from the hypochondrium by a large fluid-filled kidney, and/or outline associated vertebral and other bony anomalies.

34. Investigations Ultrasonography D emonstrate filling, dilated, or narrow posterior urethra or the presence of intraluminal lesions. Size and shape of the kidneys bladder as well as dilated pelvicaliceal system and ureter. US should be performed with a moderately filled urinary bladder, and if an anomaly is found, US should be repeated with the bladder empty. It can be used to estimate the post void residual volume of urine, and a spinal ultrasound in children younger than 3 months of age is useful for spinal lesions (tethering, defects, or masses)

35. Investigations CT scan/MRI Done with or without contrast enhancement Provide precise anatomical details of the lesion E xtent of damage Good-quality ultrasound with Doppler is a good substitute.

36. Investigations Micturating cystourethrography E ssential for demonstration of bladder shape and capacity, including diverticulum and vesicoureteric reflux and grading, posterior urethral dilatation, and possible filling defects and urinary incontinence. A filling phase is important to identify ureterocoele

37. Investigations Scintigraphy Dimercaptosuccinic acid (DMSA) scintigraphy is a radionuclide technique that provides a functional cortical map of the kidney, quantifying renal tubular cell mass. U seful for identifying scars of reflux nephropathy and estimating differential function, provided there is no obstruction. D iethylenetriamine penta -acetic acid (DTPA) scintigram , the DTPA is filtered by the glomerulus and gives a dynamic study similar to an IVU. It identifies dilatation and obstruction, and in the latter stages of the study it can give information concerning reflux. Differential renal function can also be quantified .

38. Investigations Intravenous urogram An IVU study shows morphology of the urinary tract, provided the kidney is working well enough. Is disappointing and sometimes dangerous in infants In the neonate, due to the low GFR, the urinary tract does not opacify well. The x-ray exposure for IVU is relatively high, and US scans are performed where possible

39. Investigations Urodynamic studies Urodynamic studies of the physiologic function of the bladder mechanics during filling and voiding used to ascertain the aetiology and epidemiology of nonneurogenic bladder sphincter dysfunction (NNBSD) with the aid of x-ray screening Egs of such studies include uroflowmetry and cystometrogram .

40. Investigations Cystourethroscopy A pproach of choice for identification and treatment of structural abnormalities. Posterior urethral valves , ureterocoeles may be treated , and Polyps May Be biopsied or resected. In the African setting, however, appropriate scopes may not be readily available or accessible for either adults or paediatric surgical services

41. Management BOO is a potentially curable form of lower urinary tract and renal disease Determinants of bladder dysfunction - Degree and duration of obstruction Early recognition and treatment are key to preventrenal function loss D efinitive treatment of mechanical causes of BOO is mostly surgical

42. Posterior Urethral Valves (PUV) History First reported by Langenbeck in 1802 (Dewan et al, 1999) Hugh Humpton Young developed Classification (Young et al, 1919) Most common anatomic cause of BOO in pediatric population in boys PUVs are not valves, have no function, are not part of normal development

43. PUV

44. PUV classification Classification(Young) Type I – 95% 2 folds extend anteroinferiorly from caudal aspect of verumontanum often fusing anteriorly at a lower level Type II - now discounted as non-obstructive folds of superficial muscle and mucosa, between the verumontanum and the bladder neck Type III – 5% Circular diaphragm with a central or eccentric narrow aperture in membranous urethra

45. PUV classification

46. Dewan and Ransley’s challenged Youngs classification; the types are secondary to urethral instrumentation C haracteristics of the urethral valve vary but include: attachment posteriorly to the distal part of the verumontanum ; a small hole adjacent to the verumontanum an oblique membrane with the distal attachment lying anteriorly paramedian parallel reinforcements; Distal ballooning with suprapubic pressure; traversing the urethral sphincter

47. PUV Incidence Incidence is between 1 in 5000 - 8000 male births Few familial cases recorded, including in siblings, but no established genetic predisposition Represent 10% of urological anomalies detected by prenatal U/S in Europe A ccounts for less than 1% of antenatally diagnosed hydronephrosis O verall mortality is 25–50%. Many foetuses are lost antenatally, and 45% of survivors have renal failure Other associated anomalies = chromosomal abnormalities, and some deformations related to the oligohydramnios.

48. PUV symptoms Severe obstruction leads to intrauterine renal failure and fetal death in utero or soon after birth from potters syndrome. Less severe obstruction allows the fetus to survive, but if not detected early leads to Septic complications from UTI and metabolic abnormalities caused by renal failure

49. PUV Diagnosis - Prenatal Fetus Prenatal U/S detects 80% of cases, 50% between 16-20 weeks Obstruction develop at 7 wks GA and are detectable by U/S by 14 wks

50. PUV Diagnosis – Prenatal U/S features Bilateral upper tract dilatation Persistently distended full bladder Predictors of poor functional outcome an early-onset renal failure Detection before 24 weeks’ gestation Bladder wall thickening Echo-bright kidneys (renal dysplasia) Oligohydramnios

51. PUV Diagnosis - Prenatal

52. PUV Treatment Fetus treatment Vesicoamniotic shunting Intrauterine valve ablation Fetal intervention still controversial because diagnosis is difficult and benefits are difficult to ascertain Fetal intervention carries high risk of mortality 43% Early diagnosis ensures early treatment and minimises risk of infection

53. . Complications Shunt blockage Migration Preterm labour Intrauterine death

54. PUV postnatal Neonate Symptoms of BOO Poor urinary stream Palpable bladder Kidneys may be palpable Urinary ascites Listlessness, poor feeding, irritability, failure to thrive

55. PUV Postnatal Infant May be asymptomatic Urinary tract infections Chronically impaired renal function manifest as poor growth

56. PUV postnatal Older child Urinary tact infections Voiding symptoms Growth retardation Treatment endoscopic ablation of the valves is the initial treatment

57. PUV postnatal diagnosis U/S – dilation of prostatic urethra and thickening of bladder wall amd also hydronephrosis VCUG – dilated prostatic urethra, valve leaflets, detrusor hypertrophy, bladder diverticula, bladder neck hypertrophy, narrow penile urethra stream and probably incomplete emptying Renal scan – assess kidney function

58. PUV Treatment Minimises risk of electrolyte disturbance and infection Primary treatment bladder drainage Antibiotics Correction of metabolic disturbances Urethral or suprapubic drainage T ransurethral valve ablation definitive RX – incision at 4 and 8 o’ clock Post op catheterisation only when significant intra op bleeding but may be left for 1 or 2 days

59. Vesicostomy and delayed valve ablation Indication markedly impaired renal function, especially deteriorating despite catheterisation , gross bilateral vesicoureteric reflux. S toma created at the apex of the bladder to minimise risk of prolapse Closure done after valve ablation, by 6–18 months, depending on the initial indication the child’s level of renal function

60. PUV treatment Urinary leaks due to high intravesical pressure Urinary ascites and perinephric collections or ‘urinomas ’ usually respond to a short period of bladder drainage. Large or persistent perirenal collections may require ultrasound-guided percutaneous aspiration or open drainage (in combination with open nephrostomy )

61. PUV treatment complications Damage to sphincters Urethral strictures haemorrhage

62. Patent Urachus Associated with drainage of urine from the umbilicus. Suspect Clear drainage from the umbilicus Investigate the urinary tract for bladder outlet obstruction in which the urachus is functioning as a relief valve A patent urachus may be approached either through the umbilicus or through an infraumbilical incision. It is important to identify all the umbilical structures for a definitive diagnosis . The patent urachus is ligated and transected at the level of the bladder; broad-based connections are closed in two layers with absorbable sutures

63. Urethral Polyps Urethral polyps are fibromuscular epithelial structures with transitional epithelium covering the surface. They may occur either in the posterior or anterior urethra. In either position , they may cause hematuria , urgency, or obstructive symptoms . Bladder ultrasound may show the polyps in the posterior urethra but VCUG and cystoscopy are diagnostic and excision through the cystoscope is usually curative . Polyps can present as congenital obstructing lesions with all of the characteristics of bladder outlet obstruction .

64. References Coran Pediatric Surgery 7 th Edition Essential of Pediatric Urology, 2 nd Edition, Edited by David FM Thomas Clinical Pediatric Nephrology, 2 nd Edition, Edited by Kanwal K Kher MD Langmans medical embryology, 12 th Edition