142 Acid–Base, Electrolyte and Renal Emergencies
ACUTE RENAL FAILURE2 Causes include:
(i) Pre-renal failure (decreased renal perfusion):
(a) shock, burns, sepsis, dehydration, low-output cardiac failure
(b) renovascular disease: renal artery stenosis, renal artery
emboli.
(ii) Intrinsic renal failure:
(a) acute tubular necrosis (ATN): ischaemia, sepsis, toxins, e.g.
gentamicin, radiographic contrast, myoglobin, ethylene
glycol
(b) acute interstitial nephritis: drugs (including antibiotics and
NSAIDs), infection, sarcoidosis, autoimmune disease, e.g.
systemic lupus erythematosus
(c) acute glomerulonephritis: post-infectious, vasculitis,
autoimmune disease, complement-related
(d) acute cortical necrosis: profound hypoperfusion, e.g. obstetric
complication with haemorrhage
(e) miscellaneous: malignant hypertension, renal vein
thrombosis.
(iii) Post-renal failure
Obstruction may be extramural, intramural or intraluminal at any
point from the renal tubule to the distal urethra. Causes include:
(a) ureteric obstruction to a single kidney, or bilateral ureteric
obstruction to both kidneys
(b) retroperitoneal fibrosis; ureteric strictures, calculi or crystal
deposition; tumours such as uterine cancer; prostatic disease
such as benign prostatic hypertrophy or malignancy.
3 Take a thorough history, including a drug history for potential nephrotoxic
agents, and obtain an accurate weight on arrival as this will help monitor
treatment progress.
4 As acute k idney injur y is associated with multiple pathologies it may present
in a variety of ways.
(i) Pre-renal failure with symptoms and signs of hypovolaemia such
as confusion, dehydration, orthostatic hypotension, oliguria and
anuria.
(ii) Nephritic syndrome with acute hypertension, haematuria with
red cell casts and dysmorphic red cells, and generalized oedema
from acute glomerular disease.
(iii) Flank pain, loin pain and microscopic or macroscopic haematuria.
5 Examine patients systematically. Look for:
(i) Volume status
(a) signs of volume depletion: hypotension, tachycardia,
decreased skin turgor, dry mucous membranes in a patient
with decreased renal perfusion associated with a pre-renal
condition