Postoperative Renal Complications
By: Matthew LeDuc M.D.
Ability to Void:
 Needs to be assessed as opioids and autonomic side effects
of regional anesthesia interfere with sphincter relaxation causing
retention
 Retention is common following urologic, inguinal and genital
surgery
 Ultrasonic bladder scan helps access bladder volume and is
less invasive than “straight cath”
 Reasonable to discharge patients prior to voiding however
plan must be in place to insure patient returns should voiding not
occur in 10-12 hours.
Renal Tubular Function:
 Urine color not useful in assessing concentrating ability
however is useful in detecting hematuria and pyuria
 Osmolarity >450 mOsm/L indicates intact tubular
concentrating ability
 Urine sodium conc. Far below serum concentrations or urine
potassium above concentrations indicates tubular viability.
 Osm, electrolyte, PH values close to serum may indicate poor
tubular function or ATN.
 Interactions of sevoflurane with dry carbon dioxide absorbents
(often found after 1st case of the day on Monday) generates
compound A, a vinyl ether that degrades to release inorganic
fluoride which can result in ATN. Note: This is very rare and it is
accepted that use of Sevo dose not seriously affect renal
function
Oliguria:
 Def: <0.5 ml/kg/hr
 Often an appropriate response to hypovolemia
 In patients w/o catheters assess interval since last voiding
and bladder volume to help differentiate oliguria from inability to
void.
 Check indwelling urinary catheters for kinking, obstruction by
blood clots or debris and for catheter tip positioned above
urinary level in the bladder.
 Aggressively evaluate oliguria if intraoperative events could
jeopardize renal function such as aortic cross clamping, severe
hyptension, possible urethral ligature or massive transfusion.
 After urine is sent for electrolytes and osm a 300-500cc NS
bolus helps to differentiate decreased tubular function from
hypovolemia.
 Persistence of low urine output despite fluid challenge,
adequate blood pressure and lasix challenge increases likelihood
of ATN, urethral obstruction, renal artery or vein occlusion or
SIADH.
Polyuria:
 Def: 4-5 ml/kg/hr
 Profuse urine output often reflects generous intraoperative
fluid administration
 Osmotic diuresis can occur if hyperglycemia and glycosuria is
present
 Sustained polyuria can indicate abnormal regulation of water
clearance or high-output renal failure.
 Diabetes insipidus (inadequate secretion of ADH from the
posterior pituitary or resistance of renal tubules to ADH results in
polydipsia, hypernatremia and high output urine)
 Causes of DI include: intracranial surgery, pituitary ablation,
head trauma or increased ICP.
 Treatment of DI: DDAVP
Reference: Paul G. Barah, Clinical Anesthesia: 5th edition 2006