Nephrology 4 Flashcards
What is haemolytic uraemia syndrome?
triad of acute renal failure, microangiopathic haemolytic anaemia and thrombocytopenia
secondary to gastrointestinal infection with verocytotoxin producing E. coli
acquired through contact with farm animals or eating uncooked beef, or, less often, Shigella
Which organs does HUS affect?
Prodrome of bloody diarrhoea-the toxin from these organisms enters the gastrointestinal mucosa and preferentially localises to the endothelial cells of the kidney, where it causes intravascular thrombogenesis
• Coagulation cascade is activated-platelets are consumed in this process and microangiopathic haemolytic anaemia results from damage to red blood cells as they circulate through the microcirculation
Brain, pancreas and heart
How does atypical HUS present?
no diarrhoeal prodrome
may be familial and frequently relapses
has a high risk of hypertension and chronic renal failure and has a high mortality
• Children with intracerebral involvement or with atypical HUS may be treated with plasma exchange or plasma infusions, but their efficacy is unproven
What follow up is needed in HUS?
• With early supportive therapy, including dialysis the typical diarrhoea associated HUS usually has a good prognosis
follow up is necessary as there may be persistent proteinuria and the development of hypertension and declining renal function in subsequent years
What is the definition of hypertension in children?
• Hypertension is blood pressure above 95th percentile for height, age & sex
What are the causes of hypertension in children?
Renal: Renal parenchymal disease, renal artery stenosis, PKD, renal tumours Coarctation of aorta Catecholamine excess: Phaechromocytoma Neuroblastoma Endocrine: Congenital adrenal hyperplasia Cushing syndrome/corticosteroid therapy Hyperthyroidism Essential hypertension
How does hypertension present?
o Vomiting o Headahces o Facial palsy o Retinopathy o Convulsions o Proteinuria FTT and cardiac failure Paroxysmal palpitations and sweating
How does antenatal detection aid urinary tract abnormalities?
early treatment of urinary tract anomalies provide an opportunity to minimise or prevent progressive renal damage
a disadvantage is that minor abnormalities are also detected, most commonly mild unilateral pelvic dilatation, which do not require intervention but may lead to over- investigation, unnecessary treatment and unwarranted parental anxiety
Which abnormalities are detectable on antenatal US screening?
Renal agenesis (absence)- severe oligohydramnios resulting in Potter syndrome
• Multicystic dysplastic kidney- a non-functioning structure with large fluid filled cysts and no renal tissue or connection to the bladder
• Autosomal dominant or recessive polycystic kidney disease
• Pelvic or horseshoe shaped kidneys
• Duplex system- varies from a bifid pelvis to complete division and two ureters
• Posterior urethral valves- a valve in the urethra which causes obstruction and reflux
• Hydronephrosis- a dilation and swelling of the kidney due to increased back pressure
How does GFR differ in children?
- The GFR is low in a newborn infant and is especially low in premature infants- at 28 weeks gestation the GFR is only 10% of the term infant
- In a term infant GFR is 15-20 ml/min per 1.73m2 but rapidly rises to a normal adult rate by the age of 2
What are the investigations available to monitor the kidney and renal systems?
o Ultrasound – provides anatomical assessment but not function
o DMSA scan – detects functional defects
o MCUG/VCUG – visualise bladder and urethral anatomy and can detect both reflux and obstruction
o MAG3 isotope scan – isotopes excreted from the blood into the urine can be measured
o Plain abdominal X-ray – spinal abnormalities and potentially renal stones
What is the antenatal treatment for posterior urethral valves?
may develop severe urinary outflow obstruction, resulting in progressive bilateral hydronephrosis, poor renal growth and declining liquor volume- with the potential to lead to pulmonary hypoplasia
• Intrauterine bladder drainage procedures to prevent severe renal damage have been attempted, but results have been disappointing
• Early delivery is rarely indicated.
What is the postnatal management for renal disease?
• Prophylactic antibiotics to prevent UTI
• As the newborn kidney has a low GFR- urine flow is low and mild outflow obstruction may not be evident in the first few days of life
USS delayed for several weeks- bilateral hydronephrosis in a male infant warrants an ultrasound shortly after birth to exclude posterior urethral valves which always requires urological intervention such as cystoscopic ablation
How does hypospadias form?
- In the male foetus the formation of the urethra occurs in a proximal to distal direction, under the influence of testosterone
- Failure to complete this results in a urethral opening proximal to the normal position on the glans
- It is a common congenital abnormality occurring in about 1 in 200 boys
What are the symptoms of hypospadias?
o Ventral urethral meatus- normally on the glans penis but can be on the corona, shaft or perineum.
o Hood dorsal foreskin- that has failed to fuse ventrally and a chordae-ventral curvature (of the penis head), severe hypospadias
Complications- cosmetic, problems urinating and erections
