Hepatorenal Syndrome

Hepatorenal Syndrome (HRS)

Definition

Hepatorenal syndrome (HRS) is a functional, potentially reversible acute kidney injury (AKI) occurring in patients with advanced cirrhosis and portal hypertension(Ascites), in the absence of intrinsic renal disease or structural kidney damage.

Epidemiology 

• Occurs in advanced decompensated cirrhosis (often Child-Pugh C)
• Triggers:
• Refractory ascites
• Spontaneous bacterial peritonitis (SBP)
• Large-volume paracentesis without albumin
• GI bleeding
• Severe alcoholic hepatitis
• Incidence:~20–40% of cirrhotics with ascites over time
• Prognosis: Very poor without treatment or transplantation

Pathophysiology 

1. Portal hypertension → ↑ shear stress
2. ↑ Splanchnic vasodilators (NO, CO, prostacyclin)
3. Splanchnic arterial vasodilation
4. ↓ Effective arterial blood volume
5. Compensatory activation of:
• RAAS
• Sympathetic nervous system
• Arginine vasopressin (ADH)

6. Intense renal vasoconstriction
7. ↓ Renal blood flow → ↓ GFR → AKI

Important Points

• Cardiac output may initially be high (hyperdynamic circulation)
• Renal hypoperfusion is functional, not structural
• Tubules remain intact → bland urine sediment

Updated Classification 

HRS-AKI (replaces old Type 1 HRS)

• Rapid rise in creatinine
• Defined using ICA-AKI criteria
• Most common and most lethal form

HRS-NonAKI(No Structural Kidney Disease)

• HRS-Acute Kidney Dysfunction : GFR reduction for <3 months,Does NOT meet AKI criteria,eGFR <60 mL/min/1.73 m²
• HRS-CKD: GFR reduction ≥3 months+eGFR: <60 mL/min/1.73 m²
• Seen with long-standing refractory ascites

Old terminology 

• Type 1 HRS → Rapidly progressive renal failure
• Type 2 HRS → Slowly progressive renal dysfunction with refractory ascites

Diagnostic Criteria (ICA 2015 / AASLD / EASL)

All must be present

1. Cirrhosis with ascites
2. AKI defined by ICA criteria
• ↑ serum creatinine ≥0.3 mg/dL in 48 h
  OR
• ≥50% increase from baseline in 7 days

3. No response after 48 hours of:

• Diuretic withdrawal
• Plasma volume expansion with albumin 1 g/kg/day (max 100 g/day)

4. Absence of shock(If volume resuscitation is needed administer crystalloid and patient should fail to respond within 24 hours of the resuscitation.)
5. No nephrotoxic drugs
6. No structural kidney disease

• Proteinuria <500 mg/day
• <50 RBCs/HPF
• Normal renal ultrasound

Probable Hepatorenal Syndrome–Acute Kidney Injury (Probable HRS-AKI)

The term probable HRS-AKI is commonly used in clinical practice when a patient with cirrhosis and AKI has a high likelihood of HRS, but the full diagnostic criteria have not yet been fulfilled (typically because albumin expansion has not yet been completed or other causes have not been completely excluded). This concept allows early initiation of evaluation and often early vasoconstrictor therapy, particularly in critically ill patients, rather than waiting 48 hours.

Definition

A patient is considered to have probable HRS-AKI when:

• Cirrhosis with ascites is present.
• AKI fulfills the International Club of Ascites (ICA) AKI criteria:
• Increase in serum creatinine ≥0.3 mg/dL within 48 hours, or
• ≥50% increase from baseline within the previous 7 days.
• There is no obvious structural kidney disease in H&P and POCUS
• Baseline MAP <65 mm 

Differential Diagnosis 

Clinical Features

• Oliguria
• Rising serum creatinine
• Dilutional hyponatremia
• Hypotension (often)
• Refractory ascites
• No hematuria or proteinuria
• Often precipitated by:
• SBP
• GI bleed
• Excess diuretics
• Sepsis

Investigations

• Serum creatinine (trend is critical as patients often have low muscle mass leading to artificially low creatinine values)
• Urine sodium, FeNa (supportive)
• Urinalysis (bland)
• Renal ultrasound (normal size, no obstruction)
• Exclude infection (blood, urine, ascitic fluid cultures)
• LFTs, INR, MELD score

Management 

1. General Measures

• Stop diuretics
• Stop nephrotoxins (NSAIDs, ACEI/ARB)
• Treat precipitating factors:
• SBP → antibiotics + albumin
• GI bleed → early control
• Optimize MAP (≥65 mmHg)

2. Plasma Expansion

• Albumin (20% or 25% preferred because it provides oncotic expansion with a smaller infused volume, reducing the risk of fluid overload.).
• 1 g/kg/day (max 100 g/day) for 2 days
• Then 40 g/day during vasoconstrictor therapy(optimal duration of albumin therapy remains unclear)
• Infuse over 4–6 hours
• Slower infusion (6–8 hours) is preferred in patients with:Heart failure,Pulmonary hypertension,Significant ascites

3. Vasoconstrictor Therapy 

• European guidelines recommend reserving vasoconstrictors for patients with HRS-AKI Stage IB (serum creatinine >1.5 g/dL) since milder forms are likely to resolve with fluid expansion alone.
• ACG guidelines (2021) and AASLD guidelines (2024) recommend vasoconstrictors for stages 2-3 AKI. 
• The goal is not to constrict renal arteries Instead Constrict dilated splanchnic circulation—Increase systemic vascular resistance—Increase MAP >15 mm above baseline.

Terlipressin -Selective V1 receptor agonist(Drug of choice)

A. Intermittent Bolus Regimen 

• Initial:1 mg IV QID
• Escalation:If no response after 2–3 days:
  → Increase stepwise to 2 mg IV every 4–6 hours
• Max dose:12 mg/day

B. Continuous Infusion (Preferred in ICU – Better Safety Profile)

• Start:2 mg/day continuous IV infusion
• Titrate:Increase every 24–48 hr based on response
• Max:12 mg/day

 Advantages:Less ischemic complications

Duration of Vasoconstrictor Therapy 

• Usually:7–14 days(Stop if No response after 4 days at maximal dose)

ADQI/ICA 2024 guidelines recommend stopping vasopressors when one of the following criteria is reached:

• Serum creatinine returns to within 0.3 mg/dL of baseline.
• Patient clearly fails to respond to vasopressors (e.g., persistent renal failure for >48 hours, or hemodialysis, or intractable anuria).
• Maximum of 14 days of therapy.
• Severe adverse reaction develops to the vasopressors. 

 Response Definitions 

Alternatives

• Norepinephrine-0.05–0.1 µg/kg/min 
• equally as effective as terlipressin
• Titrate every 15–30 minutes
• Midodrine(Oral α1 agonist) + Octreotide(Somatostatin analogue)
• Less effective
• Used where terlipressin unavailable.
• Not for ICU use.
• Midodrine is started at 10 mg PO q8hrs and titrated(15 mg three times daily) to increase the MAP by >10-15 mm Hg
• Octreotide-200 mcg subcutaneously every 8 hours.

Current AASLD (2021), EASL (2023), and ICA-ADQI (2024) guidelines do not recommend routine bridging to midodrine after successful treatment of HRS-AKI.

4. Renal Replacement Therapy (RRT)-Continuous renal replacement therapy (CRRT) Preferred 

• Bridge to liver transplantation
• Indications same as other AKI:
• Refractory hyperkalemia
• Severe acidosis
• Volume overload
• Uremic complications
• Poor long-term survival without transplant

5. Definitive Therapy – Liver Transplantation

• Only curative treatment
• Renal function often recovers post-transplant
• Prolonged HRS → risk of irreversible kidney injury → may require combined liver-kidney transplant

6. Types of Hyponatremia in HRS

Prevention

• Albumin during SBP (1.5 g/kg day 1, 1 g/kg day 3)
• Albumin after large-volume paracentesis (>5 L)
• Early treatment of infections
• Avoid nephrotoxins
• Careful diuretic dosing

Prognosis

• Untreated HRS-AKI:Median survival: weeks
• With vasoconstrictors:Reversal in ~40–50%
• Best outcomes with early diagnosis and transplantation