What is the main cause of anaemia in CKD?
Decreased production of erythropoietin
Why do preterm infants <34 weeks have a low GFR?
Low GFR in preterm infants is due to:
- Low renal blood flow
- The preterm infant kidney is less able to concentrate urine secondary to relatively low interstitial urea concentration, anatomically shorter loop of Henle, distal tubular and collecting duct system less responsive to ADH.
What is the main site of K+ reabsorption in the nephron?
Mostly reabsorbed in the Proximal convoluted tubule (60-70%) via the Na+/K+ ATPase and (25-35%) in the loop of Henle via Na/K/2CL co-transporter mechanism
What is normal anion gap range?
What are the causes of high serum anion gap?
a) Anion gap range 12+/-4 meq/L
AG=(Na + K) -(HCO3 +Cl-)
b) CAT MUDPILES
CO, Alcohol, Toulene, Methanol, Uremia, DKA, Paraldehyde, Iron/Isoniazid, Inborn errors of metabolism, Lactic acidosis, Ethanol, Salicylate
What is the management of nocturnal enuresis in a 10 year old? She has no daytime symptoms.
- Nocturnal enuresis is involuntary voiding at night after 5yrs of age. By age 5, 80-85% of children are continent at night and 90-95% during the day
- First line Mx: Restrict fluid intake after 6 pm, mx constipation, avoid caffeinated drinks, motivational therapy, conditioning therapy-alarm attached to sensor
- 2nd line Mx: Medication desmopressin acetate
- Answer: Enuresis alarm (alarm therapy for 16 weeks or until 14 days of being dry)
What is the function of 1,25 dihydroxycholecalciferol?
1,25-Vitam in D results in:
a) Decreased calcium and phosphate excretion by the kidney
b) Calcium and phosphate absorption from
the small intestine
c) Increased osteoclast activity and bone turnover (via PTH)
Where is renin produced and what is its function?
What is the main stimulus for renin secretion?
a) Renin is produced by juxta-glomerular apparatus (in affarent arterioles) and converts angiotensinogen (liver) to angiotensin.
b) Low Na+ stimulates renin production while high plasma Na+ levels reduces renin
In clinical practice what is used to estimate GFR?
Creatinine clearance is used to estimate GFR however note that it overestimates GFR by 10-20% due to tubular secretion of creatinine
What is Fractional Excreation (FE) of Sodium?
How do you interpret results?
a) The fractional excretion of sodium (FENa) measures the % of filtered Na+ that is excreted in the urine. It is used to differentiate prerenal disease (decreased renal perfusion) from acute tubular necrosis (ATN) as the cause of acute kidney injury.
b) FENa <1% suggests prerenal disease, where the reabsorption of almost all of the filtered Na represents an appropriate response to decreased renal perfusion, a value between 1 and 2 % may be seen with either disorder, while a value above 2% usually indicates ATN.
Note: In younger children/neonates due to limited ability of tubules to reabsorb Na+ cut offs are higher <3% pre-renal and >4% post renal
What is the MOA and indication of tacrolimus?
What are the adverse effects of tacrolimus?
a) Tacrolimus is a calcinuerin inhibitor.
- Inhibition of calcineurin in activated T cells prevents increase in cytokine production which stimulates B and T cell proliferation and differentiation.
b) Indications of tacrolimus
- prevention of solid organ transplant rejection
- prevention of GVHD in allogenic stem cell transfusion
- Induction and maintenance of remission in immune and inflammatory disorders
c) Adverse effects: Alopecia, HTN, nephrotoxicity, hypercholestrolaemia (minor effect compared to cyclosporin, and sirolimus), hyperglycaemia, hypomagnesemia, tremor, parasthesias, gingival hyperplasia. Rarely-seizures, coma, psychosis
What factors lead to progressive renal failure?
- Hyperfiltration injury
- Proteinuria
- Uncontrolled HTN
- Hypercalcaemia
- Hyperphosphatemia (leads to calcium-phosphate deposition in the renal interstitium and blood vessels)
- Hyperlipidaemia (results in oxidant mediated injury)
What is the prognosis of minimal change GN?
- MCGN is steroid responsive in most children
- 30% of treated patients are cured after the initial course of therapy
- 10-20% will relapse after steroid Rx is discontinued but will have <4 steroid responsiveepisodes before permanent remission occurs
- 30-40% will have frequent relapses (4 or more relapses per year)
In acute hypovolaemia what mediator produces dilation of the renal afferent arteriole?
Prostaglandin I 2-Found in vascular endothelial cells, it is a potent vasodilator and inhibitor of platelet aggregation
