Nephrology And Genito Urinary Notes

Nephrology and Genito-Urinary

Assessment of Renal Function in Children

• Plasma Creatinine Concentration

  • Rises progressively throughout childhood according to height and muscle bulk

  • May not be outside normal until renal function has fallen by half

• eGFR

  • = k x height (cm) / creatinine (umol/L)

  • Useful for monitoring renal function

• Inulin or EDTA Glomerular Filtration Rate

  • More accurate as clearance from the plasma of substances freely filtered at the glomerulus, and is not secreetd or reabsorbed by the tubules.

• Creatinine Clearance

  • Requires timed urine collection and blood tests – rarely used

• Plasma Urea Concentration

  • Increased in renal failure often early indicator

  • Urea increased by high protein diet and in a catabolic state

Radiological Investigation of the Kidneys and Urinary Tract

• Ultrasound

  • Anatomy NOT function

  • Visualise dilation, stones and nephrocalcinosis

  • Non invasive and mobile

• DMSA scan (^99mTc dimercaptosuccinic acid)

  • Static scan of renal cortex

  • Detects functional defetcs such as scars

  • V. sensitive wait at least 2 months post UTI to avoid diagnosing false scars

• Micturating Cystourethrogram (MCUG)

  • Anatomy and vesicoureteric reflux (VUR) and urtheral obstruction

  • Invasive and unpleasant, high radiation

• MAG3 Renogram (Mercapto-acetyl-triglycine, labelled with ^99mTc)

  • Dynamic scan

  • Label excreted from blood into urine

  • Measures drinage

  • Scan during micturition can identify VUR

• Plain Abdominal XR

  • Spinal abnormalities

  • Renal stones may be identifiable

  • Poor at showing nephrocalcinosis

Congenital Abnormalities

Diagnosis on Antenatal USS

• Renal Agenesis

  • Severe oligohydramnios (no urine production) resulting in Potter Syndrome fatality

  • Potter Facies:

    • Low-set ears

    • Beaked nose

    • Prominent epicanthic folds

    • Downward slanting eyes

  • Pulmonary hypoplasia respiratory failure

  • Limb deformities talipes

• Multicystic Dysplastic Kidney (MCDK)

  • Failure of union of the ureteric bud with the nephrogenic mesenchyme

  • Non functioning structure with large fluid filled cysts no renal tissue and no connection with the bladder

  • Half involute by 2 years but nephrectomy may be indicated

  • Potter syndrome if bilateral

  • Other causes of cystic kidneys

    • Recessive polycystic kidney disease (ARPKD)

    • Autosomal dominant polycystic kidney disease (ADPKD)

      • 1 in 1000

      • Hypertension and haematuria in childhood

      • Usually manifests in adult life

      • Multiorgan involvement:

        • Intracranial aneurysm

        • Liver and pancreatic cysts

        • Mitral valve prolapse

    • Tuberous sclerosis

      • Autosomal dominant

      • Hamartomas in the brain, skin and other organs

      • Infantile spasm, seizure and metal retardation

      • Hypomelanotic macules (ash leaf spots)

Postnatal Mangement of Anomalies

Antenatal diagnosis of urinary tract anomaly

Start prophylactic antibiotics

• Bilateral hydronephrosis and /or dilated urinary tract in a male

• USS within 48 hours (rule out posterior urerthal valves)

• Abnormal MCUG/ surgery

• Normal stop antibiotics and repeat USS at 3/12

• Unilateral hydronephrosis in a male / Any anomaly in a female

• USS at 4-6 weeks*

• Normal stop antibiotics and repeat USS at 3/12

• Abnormal further investigation

*Newborn kidney has low GFR, urine flow and mild outflow obstruction – therefore delay USS

EXCEPT in bilateral hydronephrosis rule out posterior urethral valves

Urinary Tract Infection

• Up to half of patients have a structural abnormality

• Pyelonephritis may damage the growing kidney by forming a scar, predisposing to hypertension and (if bilateral) chronic renal failure

Clinical Features

• Varies accoring to age

• Infants non specific

  • Fever

  • Vomiting

  • Lethargy / irritability

  • Poor feeding / FTT

  • Jaundice

  • Septicaemia

  • Febrile convulsions

  • Offensive urine

• Children

  • Dysuria and frequency

  • Abdo pain or loin tenderness

  • Fever with rigors

  • Lethargy / anorexia

  • Vomiting / diarrhoea

  • Haematuria

  • Offensive / cloudy urine

  • Febrile convulsion

  • Recurrence of enuresis

Collection of Samples and Investigation

**Urine sample should be tested in ALL children with unexplained fever >38^oC**

• For a child still in nappies

  • Clean-catch

  • Adhesive plastic bag

  • Urethral catheter

  • Suprapubic aspiration (SPA)

• Older children

  • MSU

    • Contamination may occur with white cells and bacteria from the foreskin

• Urine sample should be microscoped and cultured IMMEDIATELY

  • Can be refrigerated to prevent overgrowth of contaminating organisms

  • Culture of 10⁵ per mm 90% chance of infection

    • Rises to 95% if two samples are +’ve

  • ANY growth in a catheter or SPA is considered +’ve

• Dipstick testing

  • Nitrite stick +’ve likely to inficate true UTI

  • Leucocyte esterase stick test for WBCs

    • NOT a reliable marker of UTI

    • Present in balanitis and vulvovaginitis

• Interpretation of Results

Further Investigation

• NICE guidance does NOT recommend USS for first UTI if there is a response to antibiotic treatment

  • Unless <6 months OR atypical / recurrent UTI

• Atypical includes

  • Seriously ill / septicaemia

  • Poor urine flow

  • Abdominal or bladder mass

  • Raised creatinine

  • Failure to respond to suitable antibiotics within 48 hours

  • Non E-coli organism

• Imaging SEE case study pg333 of Illustrated for pics

  • USS

  • DSMA check for scarring 4-6 months later

  • MCUG obstruction or reflux

  • <6 months

    • First time UTI that RESPONDS to treatment

      • USS within 6 weeks of UTI

        • Consider MCUG if abnormal

    • Atypical or recurrent

      • USS during acute infection

      • MCUG (give prophylactic antibiotics)

      • DSMA 4-6 months post infection detects renal parenchymal defects

  • ...

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