Renal disease in a child (nephrotic syndrome, renal failure, acute glomerulonephritis) Flashcards
List some conditions with a raised anion gap.
- DKA
- Renal failure
- Poisoning with salicylate, ethanol/methanol, paraldehyde
- Inborn errors of metabolism
NB: There will be a normal anion gap in:
- Intestinal loss of base e.g. diarrhoea
- Renal loss of base e.g. renal tubular acidosis types 1 and type 2
Which electrolyte is high in renal failure? What other blood investigations will be raised?
- Potassium (normal range 3.5-4.7 mmol/L)
- Plasma urea often starts rising before creatinine
Should measure: serum Cr, urea, electrolytes, acid-base status, calcium and phosphate.
Apart from renal failure, what are the other reasons for a raised urea?
- High protein diet
- Catabolic state
- GI bleeding
What are the main non-radiological investigations for assessing kidney function in a child?
- Plasma creatinine concentration
- Calculating eGFR from formula using height and creatinine
- Inulin or EDTA GFR
- Creatinine clearance
- Plasma urea concentration
What radiological investigations of the kidneys and urinary tract are useful in children?
US - visualises urinary tract dilatation, stones and nephrocalcinosis
DMSA - detects functional defect, nucelar scan
MCUG - contrast introduced into bladder through catheter
MAG3 renogram - isotope-labelled scan to measure drainage
Plain abdo XR - spinal abnormalities and stones mainly
How are the causes of AKI classified? Give examples of causes in each group.
- prerenal: the most common cause in children
- renal: there is salt and water retention; blood, protein, and casts are often present in the urine; and there may be symptoms specific to an accompanying disease [e.g. haemolytic uraemic syndrome (HUS)]
- postrenal: from urinary obstruction.
What is the brief management of AKI based on cause (prerenal/renal/postrenal)?
Prerenal failure - suggested by hypovolaemia, low fractional excretion of sodium is as the body tries to retain volume. Correct hypovolaemia urgently with _fluid replacement and circulatory suppor_t to avoid ATI and necrosis.
Renal failure - if circulatory overload, restriction of fluid intake and challenge with a diuretic to increase urine output sufficiently to allow gradual correction of sodium and water balance. A high-calorie, normal protein feed will decrease catabolism, uraemia, and hyperkalaemia. If the cause of renal failure is not obvious, a renal biopsy should be performed to identify rapidly progressive glomerulonephritis, as this may need immediate treatment with immunosuppression.
Postrenal failure - assess the site of obstruction and relieve by nephrostomy or bladder catheterization.
What are the two most common renal causes of acute renal failure in children
The two most common renal causes of acute renal failure in children in the UK are:
- HUS
- ATN
the latter usually in the setting of multisystem failure in the intensive care unit or following cardiac surgery.
How do you correct these metabolic abnormalities in renal failure?
When is dialysis indicated in AKI?
BMJ general indications for dialysis:
- intractable hyperkalaemia;
- acidosis;
- uraemic symptoms (nausea, pruritus, malaise);
- therapy-resistant fluid overload;
What is HUS?
Triad of:
- Acute renal failure
- Microangiopathic haemolytic anaemia
- Thrombocytopenia
Usually secondary to GI infection with verocytotoxin producing E. coli O157:H7 or sometimes Shigella. Follows a prodrome of bloody diarrhoea. Toxin enters the endothelial kidney cells and causes intravascular thrombogenesis so platelets are consumed.
What are the long-term complications of HUS if left untreated?
Persistent proteinuria
Hypertension
Progressive chronic kidney disease
How do you grade the severity of CKD?
How common is CKD in children?
10 per million (i.e. very uncommon)
Congenital and familial causes are more common in childhood than acquired causes
What are the clinical features of stage4/5 CKD in children?
- anorexia and lethargy
- polydipsia and polyuria
- faltering growth/growth failure
- bony deformities from renal osteodystrophy (renal rickets)
- hypertension
- acute-on-chronic renal failure (precipitated by infection or dehydration)
- incidental finding of proteinuria
- unexplained normochromic, normocytic anaemia
What is stage 5 CKD by definition?
eGFR <15 ml/min per 1.73m2
end-stage renal failure
renal replacement therapy required
What are the most common causes of CKD in children?
Cause - %
- Renal dysplasia ± reflux - 34
- Obstructive uropathy - 18
- Glomerular disease - 10
- Congenital nephrotic syndrome - 10
- Tubulointerstitial diseases - 7
- Renovascular disease - 5
- Polycystic kidney disease - 4
- Metabolic - 4
When do symptoms usually begin with CKD?
When renal function falls to less than one third of normal or CKD stage 4
How is CKD managed?
Aims to prevent symptoms, metabolic abnormaities and allow normal growth.
Diet - calorie supplements and NG tube, sufficient protein to maintain growth but not to accumlate toxix metabolic by-products
Phosphate restriction/binder and activated vitamin D - prevents renal ostedystrophy (from secondary parathyroidism)
Salt and water balance - may need salt supplements and water, with bicarbonate supplements to prevent acidosis
Recombinant human EPO - prevents anaemia and the toxic metabolites which circulate in anaemia and are toxic to BM
Hormonal abnormalities - GH resistance may be found which can be treated with GH up to 5yrs of age, delayed puberty, subnormal pubertal growth spurt
Dialysis and transplantation - all children can have RRT when CKD stage 5 is reached but transplantation is better (although weight of 10kg needs to be reached first to avoid renal vein thrombosis)
What are the clinical features of steroid-sensitive nephrotic syndrome?
- age between 1–10 years
- no macroscopic haematuria
- normal blood pressure
- normal complement levels
- normal renal function.
What is the prognosis with steroid-sensitive nephrotic syndrome?
No progression to CKD
Proteinuria resolves in ~11 days
- 1/3 resolve directly
- 1/3 have infrequent relapses
- 1/3 have frequent relapses
