First off, however, it is important to be skeptical when somebody tells you that a liver patient's renal failure is due to HRS. HRS is actually the 3rd most common cause of acute renal failure in patients with liver disease, with the first 2 common being pre-renal failure (often 2/2 overdiuresis) and ATN. The diagnostic criteria, as defined by the International Ascites Club, are shown below:
1. cirrhosis with ascites
2. serum creatinine >1.5mg/dL
3. no improvement in serum creatinine (decrease to a level <1.5mg/dl)>
4. no current or recent exposure to nephrotoxic drugs (e.g., NSAIDs, iv contrast)
5. absence of parenchymal kidney disease as indicated by proteinuria >500mg/day, >50 RBC/hpf on urinalysis, and/or abnormal renal ultrasonography.
In my own experience, hypotension is something that goes hand-in-hand with HRS; if a patient is hypertensive, one should probably entertain diagnoses other than HRS as the cause of AKI. The urine sodium is almost always low unless the patient has recently been on diuretics. Also, hypervolemic hyponatremia is another finding which is commonly linked to HRS. Also, the presence of sepsis or SBP do not exclude the diagnosis of HRS; it is quite common in fact for these to be precipitants, although you need to look at the urine to exclude muddy brown casts/ATN (the urine sediment in HRS is typically bland).