Flashcards in Kidney and Urinary Tract Disorders Deck (127)
GFR at 28 weeks gestation compared to term infant
At 28 weeks the GFR is only 10% of term infant
GFR at term
15-20ml/min per 1.73m2
Changes in GFR post-partum
Rapidly rises to 1-2 years of age when adult rate of 80-120ml/min per 1.73m2 is reached
How are congenital renal abnormalities identified?
Before antenatal US they wouldn't be detected until caused symptoms in infancy/childhood or occasionally adulthood - now detected in utero
What is renal agenesis?
Absence of both kidneys congenitally
What is Potters syndrome?
Oligohydramnios due to decreased urine production due to renal problems (as urine makes up majority of amniotic fluid) leading to fatal condition
Symptoms of Potters syndrome?
Specific facies with low-set ears, beaked nose, prominent epicanthic folds
May be stillborn or die soon after birth due to resp. failure
Plasma Creatinine concentration in children
Main test of renal function
Rises progressively throughout childhood according to height and muscle bulk
eGFR in children
Better measure of renal function than creatinine and useful to monitor renal function serially in children with renal impairment
Inulin or EDTA GFR in children
More accurate as clearance from plasma of substrates freely filtered and not secreted or reabsorbed - but need for repeated blood tests limits use in children
Creatinine clearance in children
Requires timed urine collection and blood tests. Rarely done in children as inconvenient and inaccurate
Plasma urea concentration in children
Same as adults
Increased in renal failure often before creatinine starts rising, raised levels may be symptomatic
What is DMSA scan?
Static scan of renal cortex - detects functional defects such as scars but v.sensitive therefore need to wait 2 months after UTI
What is Micturating cystourethrogram?
MCUG - contrast into bladder through urethral catheter - visualise bladder and urethral anatomy - detects reflux and obstruction
What is MAG3 renogram?
Dynamic isotope scan - measures urinary drainage - best performed with high urine flow
In children >4 (can cooperate) can identify reflux
What is multicystic dysplastic kidney (MCDK)?
Results from failure of union of ureteric bud (ureter/pelvis/calyces/collecting duct) with nephrogenic mesenchyme
Therefore leaves non-functioning structure with multiple large fluid-filled cysts - no renal tissue and no collection to bladder
What happens normally to MCDK?
Half will have involuted by 2 years of age
Nephrectomy only indicated if remains large or hypertension develops (rare)
What is risk with MCDK?
Produce no urine therefore if bilateral will get Potters syndrome
Other causes of large cystic kidneys other than MCDK?
Autosomal recessive and autosomal dominant polycystic kidney disease and tuberous sclerosis
Difference between other cystic kidney disorders and MCDK?
Bilateral BUT some or normal renal function is maintained
Main symptoms of ADPKD in childhood?
Renal failure in late adulthood
Extra-renal symptoms with ADPKD? x4
Cysts in liver and pancreas, cerebral aneurysms and mitral valve prolapse
What can abnormal caudal renal migration lead to x2 and possible consequence x2?
Pelvic kidney or horseshoe kidney (lower poles fused in midline) can predispose to infection or obstruction
What does premature division of the ureteric bud lead to?
Duplex system - can be bifid pelvis or complete division with two ureters
Consequence of duplex system x3
Ureters frequently have abnormal drainage so ureter from lower pole moiety often refluxes, whereas upper pole may drain ectopically into urethra or vagina or may prolapse into bladder - therefore obstruction
What is bladder extrophy?
Exposed bladder mucosa as a result of failure of fusion of infraumbilical midline
What is absent musculature syndrome/prune belly syndrome?
Absence or severe deficiency of anterior abdominal wall muscles - frequently associated with a large bladder and dilated ureters and cryptorchidism
Where can obstruction occur in boys?
Posterior urethra due to mucosal folds or a membrane called posterior urethral valves
What can occur in severe obstruction
Dysplastic kidney - small, poorly functioning and may contain cysts and aberrant embryonic tissue
Most severe = Potters syndrome