A guide to diagnosing and managing ascites in cirrhosis

We suggest a systematic and targeted approach to using various physical exam maneuvers described in the literature. If the patient has a full/distended abdomen, percuss the flanks. If increased dullness at the flanks is detected, check for shifting dullness, which indicates at least 1500 mL of fluid in the abdomen.¹⁶ Keep in mind that a 10% chance of ascites exists even if shifting dullness is absent.¹⁷ Maneuvers such as the puddle sign and fluid thrill are less accurate than shifting dullness, which has 83% sensitivity and 56% specificity in detecting ascites.¹⁷ Patients with cirrhosis also have a high likelihood of complications from ascites such as inguinal, umbilical, and other hernias.

Diagnostic work-up includes blood tests and ultrasound

Blood tests. The initial work-up for ascites should include complete blood count, complete metabolic panel, and prothrombin time/international normalized ratio.¹⁸

Abdominal ultrasound is recommended as the first-line imaging test.¹⁹ Aside from detecting ascites, it can give an estimate of the volume of ascites and indicate whether it is amenable to paracentesis. A vascular exam added to the standard ultrasound can detect radiologic evidence of portal hypertension such as splenomegaly, portosystemic collaterals, splenorenal shunt, patency of the paraumbilical vein, and portal vein diameter. Patients with established cirrhosis also require abdominal ultrasound every 6 months to screen for hepatocellular cancer.²⁰

Abdominal paracentesis is the cornerstone of ascites evaluation.²¹ It is indicated for every patient with new-onset ascites or for any patient with known ascites and clinical deterioration. Ascitic fluid analysis can be used to easily differentiate portal hypertension from other causes of ascites. It can also be used to rule out bacterial peritonitis. The recommended sites for evaluation are in the left lower quadrant, 3 cm cranially and 3 cm medially from the anterior superior iliac spine.²² A large cohort study showed that abdominal ultrasound-guided paracentesis reduced bleeding complications by 68% following the procedure and is strongly recommended (if available).²³ Generally, paracentesis is a relatively safe procedure with a low risk of complications such as abdominal wall hematoma (1%), hemoperitoneum (< 0.1%), bowel perforation (< 0.1%), and infection (< 0.1%).²⁴

Calculating the serum ascites albumin gradient better characterizes ascitic fluid than total protein-based tests.

Assess all ascitic fluid samples for color, consistency, cell count and differential, albumin, and total protein. These tests are usually sufficient to provide evidence regarding the cause of ascites. If there is suspicion of infection, order a gram stain and culture (80% sensitivity for detecting an infection if obtained prior to initiation of antibiotics)²⁵ and glucose, lactate dehydrogenase (useful to differentiate primary from secondary bacterial peritonitis),²⁶ and amylase tests. Other tests such as cytology, acid-fast bacilli smear and culture, and triglyceride level should only be obtained if specific conditions are suspected based on high pretest probabilities.

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