URINARY TRACT MALFORMATIONS AND INFECTIONS

•	Abnormalities of renal development.
•	Urinary tract infections.
•	Diagnostic investigations.
•	Vesicoureteric reflux.

Abnormalities of renal development

1.	Potter sequence

a.	This involves:

i.	pulmonary hypoplasia.

ii.	typical facies: widespaced eyes, epicanthic folds, broad flat nose, low-set ears, small chin.

iii.	limb abnormalities.

b.	It is due to severe oligohydramnios from:

i.	renal agenesis (20%).

ii.	autosomal recessive polycystic kidney disease.

iii.	medullary dysplasia.

iv.	renal obstruction.

2.	Renal dysplasia.

a.	Cysts of varying size are found in the kidney.

b.	Abnormal tissues such as cartilage and smooth muscle are present.

c.	It may present as an abdominal mass at birth.

3.	Infantile polycystic kidney disease

a.	Autosomal recessive condition.

b.	There is dilatation of collecting ducts to form sausaged shaped cysts.

c.	Characterized by:

i.	renal: cysts, haematuria, hypertension, polyuria; CRF develops in 5 – 10 years.

ii.	liver: cysts, hepatic fibrosis and portal hypertension.

iii.	pulmonary hypoplasia.

4.	Medullary cystic disease

a.	Autosomal recessive condition.

b.	One of the most common causes of end stage renal failure in childhood.

c.	Presentation is at the ages of 3 – 7 years with growth failure, anaemia, polyuria and polydipsia.

5.	Posterior urethral valves

a.	These are the most common cause of anatomical bladder outlet obstruction in boys.

b.	The kidneys are often affected by back pressure.

c.	Newborn babies may present with abdominal distension and dribbling or retention of urine; older children often develop sepsis or failure to thrive.

d.	The diagnosis is made on MCU.

e.	The valves can be ablated surgically and complex surgical reconstruction of the urinary tract is often necessary. 

6.	Neurogenic bladder

a.	Found commonly in association with spina bifida.

b.	The bladder is usually large and does not empty completely.

c.	The aim of management is to keep the bladder drained and thereby prevent urinary infection and damage to the kidney; this is usually done by clean intermittent catheterization.

7.	Prune belly syndrome

a.	An association of:

i.	deficient abdominal wall muscles.

ii.	undescended testes.

iii.	urinary tract abnormalities.

b.	May be due to severe urethral obstruction early in intrauterine life. 

8.	Duplication of kidneys

a.	Can be complete or incomplete and is not necessarily symptomatic.

b.	In total duplication there are two distinct ureters; the ureter from the upper pole of the kidney drains to a site distal to the drainage site of the ureter from the lower pole of the kidney.

c.	This upper pole ureter may drain to a site outside the bladder and give rise to incontinence or may be obstructed at its distal end.

d.	The lower pole ureter has an increased tendency to reflux. 

Urinary tract infection

1.	Significance of UTI in childhood

a.	Occurs in 3% of girls and 1% of boys; 50% of these children have a structural abnormality.

b.	UTI in infants may be associated with bacteremia and sepsis.

c.	Association with vesicoureteric reflux.

d.	Indicator of an underlying congenital abnormality that may require surgery.

e.	Pyelonephritis and urinary tract malformations form a major cause of chronic renal failure in children.

2.	Pathology

a.	A UTI can present as:

i.	acute cystitis.

ii.	acute pyelonephritis.

iii.	asymptomatic bacteriuria.

iv.	septicaemia.

b.	Acute pyelonephritis may lead to renal scarring and changes of chronic pyelonephritis.

c.	UTI associated with reflux can cause scarring in a growing kidney and this can lead to hypertension and chronic renal failure.

3.	Symptomatic UTI in children

a.	Frequency.

b.	Urgency.

c.	Dysuria.

d.	Enuresis.

e.	Cloudy urine.

f.	Loin pain.

g.	Abdominal pain. 

4.	Non-specificity of signs and symptoms in infants

a.	Fever of unexplained origin.

b.	Convulsions.

c.	Feeding problems.

d.	Vomiting.

e.	Diarrhoea.

f.	Jaundice.

g.	Failure to thrive.

h.	Screaming attacks. 

5.	Epidemiology

Organisms	% of cases	
E. coli	68 – 81	
Klebsiella	4.4 – 10 	
Proteus	4.4 – 6	
Enterococcus	10	

6.	Screening for UTI

a.	Chemical test strip:

i.	detection of nitrites.

ii.	detection of leucocytes esterases.

b.	Pyuria:

i.	boys: > 10 / ul uncentrifuged urine.

ii.	girls: > 50 / ul uncentrifuged urine.

c.	Bacteria seen on direct microscopy.

7.	Methods of urine collection

a.	Midstream specimen:

i.	the presence of 105 bacteria / ml or more in a midstream specimen indicates UTI, so long as the growth is of a single organism.

ii.	a mixed growth suggests contamination.

iii.	a growth of < 104 / ml indicates that the urine is sterile.

iv.	ideal for children who are continent and can void on request.

b.	Bag urine specimens:

i.	contamination is common.

ii.	suitable only for excluding UTI by the finding of a growth of < 104 / ml.

c.	Suprapubic aspiration of urine:

i.	most accurate way of collecting urine for confirmation of infection in children aged less than 2 years.

ii.	it is safe and simple.

iii.	it is performed when the child has not voided for at least 1 hour.

iv.	after skin preparation, a 23 gauge needle attached to a syringe is inserted vertically just above the pubic symphysis with steady suction being applied until urine is obtained. 

v.	because bladder urine should be totally sterile, the presence of any organisms on culture indicates infectioin.

d.	Catheter urine specimens: used only where there has been failure to obtain urine by suprapubic aspiration.

e.	In all cases, the urine specimen should either be taken direct to the laboratory or refrigerated, as room temperature encourages the growth of organisms.

8.	Treatment of Lower UTI

Antibiotics	Dosage	Duration	
Cotrimoxazole	40 mg / kg / day	< 7 years: 7 – 10 days.
> 12 years: 3 days.
7 – 12 years: decide individually. 	
Nitrofurantoin	5 – 7 mg / kg / day		
Cephalexin	50 mg / kg / day		
Trimethoprim	6 – 8 mg / kg / day		

9.	Treatment of Upper UTI

a.	Infant < 28 days:

i.	ampicillin: 50 – 100 mg / kg / day.

ii.	gentamicin: 5 – 6 mg / kg / day.

b.	Infant > 28 days and child: gentamicin 7.5 mg / kg / day.

c.	For both age groups:

i.	ceftriaxone: 50 – 100 mg / kg / day.

ii.	cefotaxime: 50 – 200 mg / kg / day.

d.	Duration:

i.	10 – 14 days.

ii.	infant < 28 days: IV therapy until no fever for 48 – 72 hours then oral therapy.

iii.	infant > 28 days: parenteral therapy until response for 24 hours then oral therapy. 

Diagnostic Investigations

1.	Renal ultrasound

a.	Non-invasive and simple, but operator dependent.

b.	Generates information on renal size and growth, structure and obstructions.

2.	Intravenous urography (IVU)

a.	Rarely needed.

b.	Outlines the kidneys and ureters, is used to determine whether there is reflux nephropathy or other abnormalities in the renal tract.

3.	Micturating cystourethrography (MCU)

a.	Radiolabelled scanning: bladder is filled with radiocontrast via a urethral catheter in place and infant voiding.

b.	The diagnosis of vesicoureteric reflux is made by observing the backflow of urine from the bladder into the ureter and kidney.

c.	The urethra is also delineated on MCU and it is thus the ideal technique for diagnosing posterior urethral valves.

4.	Static nuclear medicine scan (DMSA)

a.	DMSA is taken up by proximal tubules and the functional cortical mass is outlined.

b.	Normal results range > 45% on kidney and < 55% the other.

c.	The scan is used to detect renal scarring and pyelonephritis.

d.	Not useful in situations where urinary obstruction is suspected.

5.	Dynamic nuclear medicine scanning (DTPA and MAG 3)

a.	DTPA and MAG3 are freely filtered through the glomerulus.

b.	In a normal scan the isotope is quickly excreted, but with pathology the excretion is delayed.

c.	Frusemide is then given to differentiate an obstructed system from an unobstructed system.

d.	Used to detect renal blood flow, function and drainage disorders and reflux in an older child who can control micturition on demand. 

Vesicoureteric reflux

1.	This is detected on renal investigation usually following UTI.

2.	It is a reflux of urine from the bladder into the ureters and renal pelvis due to incompetence at the vesicoureteric junction or abnormality of the whole ureter. 

3.	Reflux can result in renal scarring because:

a.	Renal pelvis exposed to high pressures.

b.	Facilitates passage of bacterial to renal pelvis.

4.	Causes

a.	Primary incompetence of VU sphincter:

i.	anatomical distortion of VU junction: congenital paraureteral diverticulum, ectopic ureter.

ii.	bladder dyssynergia.

b.	Secondary causes:

i.	infection.

ii.	posterior urethral valves.

iii.	neurogenic bladder. 

c.	Childhood causes of neuropathic bladders:

i.	spina bifida.

ii.	sacral agenesis.

iii.	autonomic neuropathy.

iv.	transverse myelitis.

v.	spinal cord tumor / trauma.

5.	Classification

Grade	Features	
Grade 1	Ureter only, with no dilatation.	
Grade 2	Up to renal collecting system without any dilatation.	
Grade 3	Into collecting system with mild / moderate dilatation and tortuosity of ureter, and mild / moderate dilatation of collecting system.	
Grade 4	As for grade 3 as well as obliteration of forniceal angles.	
Grade 5	Gross dilatation and tortuosity of ureter, gross dilatation of renal pelvis and calyces. 	

6.	Management

a.	Aims:

i.	preservation of renal function and continence.

ii.	enable child to lead as normal a life as possible.

b.	Long-term prophylactic antibiotic therapy.

c.	Routine MSU 3 – 4 monthly or when symptomatic.

d.	BP check six-monthly for life.