NEPHROLOGY
ACUTE RENAL FAILURE
Even when 90% of the nephrons are destroyed , the kidney function
is yet normal.
In hypovolumia or shock if prolonged , acute Tubular Necrosis develops and less than
500 ml of urine is passed daily.
Vomiting
rids the body of Potassium ( decreases Hyperkalaemia ) and sodium,
BP
rises in an attempt to increase renal perfusion ,
Anorexia
ensures low protein input and thereby decreasing production of Blood urea nitrogen.
Eventually
gradual increase in urine output occurs and diuretic phase may develop which
reduces the retained sodium, potassium and urea.
Outcome
is not decided by the Renal failure but by the underlying cause.
No
treatment as yet is known to reduce the duration of Acute Tubular Necrosis.
CHRONIC RENAL FAILURE
i)
It is an irreversible deterioration
of renal function . It is apparent only after GFR ( Glomerular Filtration Rate ) falls from 120 ml / min to 20ml / min . The
skin takes over and excretes the increased Urea, etc in the sweat.
ii)
Metabolic Acidosis resulting
from diminished excretion of acids is compensated by the loss of chloride ions in vomiting or sweating.
iii)
Increased nitrogenous excretion
occurs via diarrhoea.
iv)
There is hyper secretion of
Renin Angiotenin, Aldosterone system which could be considered beneficial to renal perfusion.
v)
Mobility and Exercise in the
patient helps to preserve muscle mass, decreased Nitrogen production and encourage carbohydrate metabolism.
vi)
Osteomalacia - The decreased
production of active Vitamin D causes a decrease in Serum Calcium as bone is eroded. The phosphorous retention by the Kidney
and the decreased Calcium indirectly stimulates the Parathyroid gland and PTH secretion and raises Serum Calcium to counter
the fall in calcium. Ultimately hyperplasia of Parathyroid gland occur and increase calcium annd increase Bone density and
counteracts the Osteomalacia. Initially PTH increase erodes bone later PTH hyperplasia densifies the bone.
vii)
Polyuria serves to increase
BUN and toxic excretion.
Raised
Urea and Creatinine (uptoCrn 14, BUN 200) can be tolerated by the body and are not necessarily toxic to the body.
URINARY
TRACT OBSTRUCTION
Usually
renal calculi settle comfortably in renal pelvis and most often causing incomplete obstruction and not interfering with the
flow.
If
they get impacted in the ureter, they are almost always passed via strong ureteric contraction called renal colic which usually
subside within 2 hours.
A
calculus takes about 3 years to form and may remain asymptomatic for years together.
Stones
less than 0.5 cm pass spontaneously and larger stones stay comfortably in the Renal pelvis.
RENAL
TRANSPLANTATION
Is
usually performed in Chronic Renal Failure where GFR has fallen radically as shown below :
GFR
CRN
NORMAL ( 150ml/min) 1mg%
50
2mg%
10
6
2
16
Complications
in CRF develop when creatinine reaches 8- 10 mg %.
Transplantation
is via a compatible Kidney graft and has a 90 % patient survival for 3 years
Long
term Immunosuppressants are required and these are themselves nephrotoxic . Immunosuppressants cause opportunistic infection
and 50 % patients develop skin cancer.
