Investigations
1st investigations to order
serum creatinine
Test
Widely available and inexpensive test. Lower levels of serum creatinine indicate greater chances of HRS reversal.[4][6][7]
Revised International Club of Ascites classification criteria specifies following changes in serum creatinine levels for HRS-AKI and HRS-NAKI:
HRS-AKI: increase in serum creatinine ≥0.3 mg/dL within 48 hours; or a percentage increase serum creatinine ≥50% from baseline which is known, or presumed, to have occurred within the prior 7 days
HRS-NAKI: increase in serum creatinine <50% using last available value of outpatient serum creatinine within 3 months as baseline
Inaccurate results may be obtained with serum creatinine test in patients with cirrhosis because of impaired creatine production (the precursor of creatinine), reduced muscle mass, tubular secretion of creatinine, and inaccurate estimate of creatinine due to interference by elevated serum bilirubin.[5][27][28]
Result
elevated serum creatinine
urea
Test
Levels may be artificially decreased because of reduced hepatic synthesis of urea or increased if gastrointestinal haemorrhage.[3]
Result
variable urea
electrolytes
Test
Low sodium due to chronic liver disease.
Potassium increases as renal failure progresses.
Result
low sodium; elevated potassium with progressive renal failure
FBC
Test
Anaemia and thrombocytopenia due to chronic liver disease.
An elevated WBC count may be suggestive of the presence of an infection, which may be responsible for the worsening renal function.
Result
low Hb; low platelets
liver tests
Test
Transaminases, gamma-glutamyltransferase, and alkaline phosphatase may be normal or elevated in chronic liver disease.
Low albumin is an indication of impaired liver function.
Result
low albumin; elevated bilirubin
coagulation study
Test
Indication of impaired liver function.
Result
prolonged prothrombin time
diagnostic paracentesis and culture of ascitic fluid
Test
Suggests spontaneous bacterial peritonitis, which commonly precipitates HRS-AKI.
Result
WBC count elevated (polymorphonuclear leukocytes >250 cells/mm³); positive culture
blood culture
Test
Positive culture suggests sepsis.
Result
may be positive for causative organism
urinalysis and culture
Test
Presence of WBC and organisms indicate a possible infectious cause of worsening renal function.
Presence of red blood cells and red cell casts suggests an intrinsic renal cause of renal failure, such as glomerulonephritis.
Urinary sodium is low in HRS due to preserved tubular function and activation of sodium-retaining systems. However, this should not be used to differentiate between HRS and acute tubular necrosis.[5][20]
Result
absence of heavy proteinuria or albuminuria (protein <500 mg/dL); sodium <10 mmol/L (10 mEq/L); urine osmolarity > plasma osmolarity; urine culture may reveal infection
Chest x-ray
Test
Chest x-ray is performed to exclude sepsis and pulmonary oedema.
Result
no sign of infection
Investigations to consider
renal ultrasound
Test
Renal ultrasound is performed to exclude an obstructive cause of renal failure.
Result
no evidence of obstruction
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